#### Star One

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« on: 10/05/2017 07:55 PM »
Blog by Seth Shostak of SETI. Just hope he’s right is all I can say and also that I am still around by then.

Quote
l’ve bet a cup of coffee to any and all that by 2035 we’ll have evidence of E.T. To many of my colleagues, that sounds like a losing proposition. For more than a half-century, a small coterie of scientists has been pursuing the Search for Extraterrestrial Intelligence, or SETI. And we haven’t found a thing.

I’m optimistic by nature—as a scientist, you have to be. But my hopeful feeling is not wishful thinking; it is firmly grounded in the logic of SETI. Half a century sounds like a long time, but the search is truly in its early days. Given the current state of SETI efforts and abilities, I feel that we’re on the cusp of learning something truly revolutionary.

Most of our experiments so far have used large radio antennas in an effort to eavesdrop on radio signals transmitted by other societies, an approach that was dramatized by Jodie Foster in the 1997 movie Contact. Unlike other alien potboilers, Contact’s portrayal of how we might search for extraterrestrials was reasonably accurate. Nonetheless, that film reinforced the common belief that SETI practitioners paw through cosmic static looking for unusual patterns, such as a string of prime numbers. The truth is simpler: We have been searching for narrow-band signals. “Narrow-band” means that a large fraction of the transmitter power is squeezed into a tiny part of the radio dial, making the transmission easier to find. This is analogous to the way a laser pointer, despite having only a few milliwatts of power, nonetheless looks bright because the energy is concentrated into a narrow wavelength range.

http://m.nautil.us/blog/why-well-have-evidence-of-aliensif-they-existby-2035

« Last Edit: 11/08/2017 07:40 PM by Star One »

#### matthewkantar

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #1 on: 10/05/2017 09:21 PM »
An inflection point for SETI will be what turns up in the search for extra terrestrial life, most likely not intelligent. This will be facilitated by next generation telescopes. Detailed spectra from exoplanets may turn up unmistakeable bio-markers. I would bet a cup of coffee this sort of result turns up before 2025. A solid result might also lead to increased funding for SETI, and for ever more powerful telescopes.

Matthew

Edited for spelling
« Last Edit: 10/21/2017 07:22 PM by matthewkantar »

#### Lar

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #2 on: 10/05/2017 09:37 PM »
I skimmed it but missed a compelling argument for why he thinks we will find something. Is it because by 2035 we will have thoroughly explored the LaGrange points and the Moon? I'm dubious of that timeline.
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#### TakeOff

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #3 on: 10/05/2017 09:54 PM »
I hope to live to see Shostak eat a porcelain coffee cup, as he promised to do. But nothing can never be indicated, so he'll glance on in MSM now and then, talking about hunting aliens.

Some French guy is said to have eaten an entire bicycle, so we should not underestimate the human digestion system as a way of taking care of problems. Just eat'em!

#### vapour_nudge

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #4 on: 10/05/2017 09:55 PM »
After so long searching fruitlessly looking for something that's not there it would be hard for anyone to admit they're wrong. So, just dig the heels in...

#### Star One

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##### Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #5 on: 10/05/2017 10:52 PM »
After so long searching fruitlessly looking for something that's not there it would be hard for anyone to admit they're wrong. So, just dig the heels in...

What a ridiculous assumption, for a start how can you say at this stage no one is there? Also we’ve barely searched much of the possible spectrum out their due to a combination of technological and budgetary limitations.

To think we are the only intelligence live in the entirety of the universe always strikes me as one of the most arrogant statements that can be made.
« Last Edit: 10/05/2017 10:57 PM by Star One »

#### vapour_nudge

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #6 on: 10/06/2017 01:15 AM »
Nowhere in my post did I mention intelligent life.  I meant any life at all. Perhaps it's time to stop searching for life and just go and look for the wonder of it all. There's so much we don't know about our own Solar system. Perhaps a lot of the money sent to SETI and otherwise similar wasteful enterprises could go towards funding more Discovery/New Horizons missions etc

I'm a sci-fi fan too but I don't believe the stuff

#### spacenut

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #7 on: 10/06/2017 01:21 AM »
If there are aliens, they may not be using our type of communication, but some other form that we cannot detect.

#### punder

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #8 on: 10/06/2017 01:25 AM »
Perhaps a lot of the money sent to SETI and otherwise similar wasteful enterprises could go towards funding more Discovery/New Horizons missions etc

Yes, that vast NASA SETI budget is such a waste! How much is it, again?

And, can you list the other government sources of SETI research, along with the funding figures, and explain how all that money could be redirected to the NASA robotic exploration budget?

#### Star One

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #9 on: 10/06/2017 07:40 AM »
If there are aliens, they may not be using our type of communication, but some other form that we cannot detect.

I’ve wondered if there is the possibility that all biological life is supplanted by machine life as an inevitability and until a similar thing happens here there will not be a detection of other intelligence.

#### sanman

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #10 on: 10/06/2017 08:44 AM »
I’ve wondered if there is the possibility that all biological life is supplanted by machine life as an inevitability and until a similar thing happens here there will not be a detection of other intelligence.

That presupposes that biological life has to be intelligent life that develops artificial machine intelligence.

Ironically, we're most likely to find extraterrestrial life if we deploy our own artificial intelligence to keep relentlessly searching for it.

#### Star One

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #11 on: 10/06/2017 09:51 AM »
I’ve wondered if there is the possibility that all biological life is supplanted by machine life as an inevitability and until a similar thing happens here there will not be a detection of other intelligence.

That presupposes that biological life has to be intelligent life that develops artificial machine intelligence.

Ironically, we're most likely to find extraterrestrial life if we deploy our own artificial intelligence to keep relentlessly searching for it.

I’ve seen it proposed that machine life wouldn’t or couldn’t talk to biological life, hence another reason for AI.

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #12 on: 10/06/2017 12:20 PM »
I tend to the "Rare Earth" hypothesis, that microbial life is common but animals are rare, and intelligent animals (almost!) vanishingly rare.  (See book by Brownlee and Ward of the same title; Brownlee was a professor of mine in college.)

It could be argued that radio SETI hinges on a few postulates: ETI exists, and they want to talk, and they want to use radio, and they want to use the frequencies we're observing.  But radio SETI is fairly low-cost, and it's unimaginably high-payoff if it succeeds, so to me, it's worth doing.

My guess is, if we get evidence of extraterrestrial life, it'll come from spectroscopic observations of extrasolar planets, microfossils from Mars, or perhaps in situ observations from Europa or Enceladus.  And it'll be a long time between the detection, and acceptance that it's actually extraterrestrial life ("extraordinary claims" and all that), unless it's something like a picture of some sort of sharktopus in the seas of Enceladus.

Sci-fi is sci-fi, but one could argue that the long history of life on Earth is evidence against the existence of Berserker planet-killing starships (see Fred Saberhagen's novels), and therefore malevolent AI in the universe.  If we ever create strong AI, we'll test the Berserker/Skynet hypothesis soon enough.

In the end, the Fermi paradox looms large.  IMHO, we're a long way from either getting positive proof, or being able to draw a negative conclusion.
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#### TakeOff

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #13 on: 10/06/2017 01:32 PM »
"Rare Earth" is certainly true in the sense that there's nothing similar to us in the visible universe. The diversity of life on Earth (although all closely related) and the diversity of the planets and exoplanets points to a huge diversity in bio-kind of chemistry. Life and other funny phenomena may be common out there. But nothing that we could communicate with or even eat (isn't that the working definition, that if we can eat it it was alive). Maybe in a world like Enceladus, life spurts out to space and falls back and gradually evolve to survive in space. Space faring bugs without any intelligence or civilization or technology.

The combinatorics of biology, even just our own as it is, is much much larger than the visible universe. Two similar things will never occur in spacetime contact of each other.
« Last Edit: 10/06/2017 01:33 PM by TakeOff »

#### M.E.T.

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #14 on: 10/06/2017 01:37 PM »
Well, how about the Universe being merely a larger version of the Earth system itself. Meaning, if life developed only once on Earth at some point (and that is a possibility at this stage), it gradually spread to and evolved  in the various environmental niches on the planet.

Eventually, it could evolve enough to spread to the next planet, where new evolutionary forces will influence it to adapt even further. Eventually it spreads to the next solar system, and eventually, presumably, to the next galaxy, until the entire Universe is populated by it. Of course, the various evolutionary forms in the various environmental niches across the Universe will ultimately differ drastically from the original species that first spread beyond the Earth's atmosphere. Just like the various species on Earth already differ significantly from one another.

In any case, the point is that life had to start somewhere, and it might as well have been on the Earth 3-4 billion years ago. Looking back from a point 100 billion years in the future, life would be common throughout the Universe. And the point where it originated would be largely irrelevant, much like the exact point of origin of it back in Earth's history is interesting, but far removed from us today.

#### su27k

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #15 on: 10/06/2017 02:58 PM »
Shouldn't the title be "If They Exist in our galaxy"?

I think there're some opinions that Drake's estimate in the Drake Equation is too optimistic, a more realistic estimate would yield 1 to 2 civilizations per galaxy only.

#### savuporo

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #16 on: 10/06/2017 03:14 PM »
I skimmed it but missed a compelling argument for why he thinks we will find something. Is it because by 2035 we will have thoroughly explored the LaGrange points and the Moon? I'm dubious of that timeline.

It read as a bit of solid autoetnographic research
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#### zubenelgenubi

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #17 on: 10/06/2017 04:49 PM »
<snip>

Sci-fi is sci-fi, but one could argue that the long history of life on Earth is evidence against the existence of Berserker planet-killing starships (see Fred Saberhagen's novels), and therefore malevolent AI in the universe.  If we ever create strong AI, we'll test the Berserker/Skynet hypothesis soon enough.

In the end, the Fermi paradox looms large.  IMHO, we're a long way from either getting positive proof, or being able to draw a negative conclusion.

Unless Gregory Benford's hypothesis/story is correct: that a new, technically advanced species starting to broadcast in the RF spectrum catches the attention of the lurking galactic machine AI civilization.  (Galactic Center saga, beginning with Into the Ocean of Night)

Why dispatch Berserkers willy-nilly, when the mechanicals can keep a lid on the biological intelligences with force-multipliers like the Snark and the Watchers?  And, the strategy answers the Fermi Paradox.

Maybe there's another good reason for a frequent-repeat, deep magnitude all-sky survey program: to observe a Snark as early as possible as it "drops" into the Solar System.

Have a nice day!
« Last Edit: 10/06/2017 04:52 PM by zubenelgenubi »

#### TakeOff

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #18 on: 10/07/2017 03:50 PM »
I think that if extraterrestrial intelligence is not discovered by 2035 or so, the interest for looking for it will diminish even more. Seth Shostak is kind of making that worse by making deadlines like that. Bbut of course to improve enthusiasm in the short term, which is a crucial step to the long term. And soon this date will be forgotten anyway. What could he say? It's his job to promote SETI, and I think this crazy guy does a very good job. And it certainly would be  a very bad idea to not even try looking.

#### Star One

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #19 on: 10/07/2017 06:24 PM »
I think that if extraterrestrial intelligence is not discovered by 2035 or so, the interest for looking for it will diminish even more. Seth Shostak is kind of making that worse by making deadlines like that. Bbut of course to improve enthusiasm in the short term, which is a crucial step to the long term. And soon this date will be forgotten anyway. What could he say? It's his job to promote SETI, and I think this crazy guy does a very good job. And it certainly would be  a very bad idea to not even try looking.

Are you implying anyone who works in SETI is crazy, because if you are that’s pretty indefensible?

#### TakeOff

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #20 on: 10/07/2017 06:42 PM »
Are you implying anyone who works in SETI is crazy, because if you are that’s pretty indefensible?
Seth Shostak certainly uses the crazy alien hunter as part of his public persona. That's how most people perceive SETI, Seth strikes the right string in the public mind. I think that without him SETI would quickly dwindle. And they haven't found anything, so it is a natural joke to everyone. A project like this has to be handled with a sense of humor.

#### Star One

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #21 on: 10/07/2017 09:01 PM »
Here’s a new related SETI article from Jason Wright.

Quote
One of the reasons SETI is hard is that we don’t know exactly what we are looking for, and part of that difficulty is that we still aren’t sure of who we are.  It seems counter-intuitive, but in order to be good at looking for aliens, we have to become experts at understanding ourselves.

http://sites.psu.edu/astrowright/2017/08/17/doing-seti-better/

#### TakeOff

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #22 on: 10/08/2017 06:18 AM »
Here’s a new related SETI article from Jason Wright.

Quote
One of the reasons SETI is hard is that we don’t know exactly what we are looking for, and part of that difficulty is that we still aren’t sure of who we are.  It seems counter-intuitive, but in order to be good at looking for aliens, we have to become experts at understanding ourselves.

http://sites.psu.edu/astrowright/2017/08/17/doing-seti-better/
That article is itself an example of "cultural myopia"!
The idea of intelligence and civilization is overdone. It is a self-glorifying geocentric perspective. No one has even the faintest idea as to what subjective consciousness is. Science can never even try to start to address the question because consciousness is an immeasurable non-objective existence. Yet our intelligence seems to build upon it, and hence our technology and civilization. We are so intelligent that we have no idea of what intelligence is! So what other non-objective non-measurable phenomena are out there, forming matter and energy like we do??

I do agree that looking for copies of ourselves is a practical approach, but the article totally fails with its claim to get out of this myopic perspective of searching for ourselves out there. Looking at ourselves in the mirrors of the space telescopes. The analogs with historic colonization on Earth can have a meaning for human colonization for space, since we are the same and repeat. But it can have no similarities with what completely different kinds of phenomena are doing. Europeans went to America to grow potatoes and tobacco. What has that got to do with anything else? I think that American history focus has taken over too much of the public thinking about these things.
« Last Edit: 10/08/2017 06:20 AM by TakeOff »

#### RotoSequence

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #23 on: 10/08/2017 10:29 AM »
I think that American history focus has taken over too much of the public thinking about these things.

Obsessing over "how awful American history is" has effectively become the dominant cultural movement in public universities in America. A myopic view isn't a surprise; the objective study of cultures has basically disappeared in the process.

In any case, it's irrelevant. We can look for optimal structures in nature and reasonably extrapolate that the same laws of physics will produce similar optimal results elsewhere, and the rules of telescope optics care not for culture or philosophy, no matter what planet they're built on.
« Last Edit: 10/08/2017 10:30 AM by RotoSequence »

#### marseventually

##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #24 on: 10/08/2017 03:11 PM »
Somewhere around the late 1960's Arthur C. Clarke predicted there was a 99% chance that we would contact intelligent ETs by the year 2000.  Ambitious predictions are often wrong.

#### Bynaus

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #25 on: 10/09/2017 07:19 AM »
I skimmed it but missed a compelling argument for why he thinks we will find something. Is it because by 2035 we will have thoroughly explored the LaGrange points and the Moon? I'm dubious of that timeline.

The way I understand it is that if the "10000 to 1 million broadcasting societies in the galaxy" estimates are right, by 2035 we will have surveyed enough near-by stars at sufficient sensitivity to have found the first broadcasting society (with high statistical likelyhood). That seems to be a fair claim.

Of course, these estimates might well be (and are very likely to be, in my opinion) way too high. Then, we won't have found ETIs by 2035, even if they exist (contrary to the claim of the headline of the article).

#### QuantumG

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #26 on: 10/09/2017 08:06 AM »
I usually don't have an opinion on this kind of thing, but it really does seem like the problem of SETI is scale (with a little bit of algorithm thrown in, I guess) and the way to solve problems of scale is *not* the academic approach. Until we figure out a way to make profit from searching for extraterrestrial signals then we'll never find them. Okay, maybe never is too harsh, without profit we won't find them until the non-related economy of relevant technology reaches a point where the required scale is in the noise. i.e., if some other industry causes the abundance of (almost certainly space) radio telescopes you reach such a level that searching for extraterrestrial signals is just a side activity then we may have a chance of finding them. Otherwise we're just searching for a needle in a haystack with grad student labor... literally.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

#### Star One

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #27 on: 10/19/2017 08:13 PM »

Why haven’t we had alien contact? Blame icy ocean worlds

Quote
Might ET be buried under too much ice to phone Earth? That’s what planetary scientist Alan Stern of the Southwest Research Institute in Boulder, Colorado, has concluded may be delaying our contact with alien civilizations. Most extraterrestrial creatures are likely deep inside their home planets, in subsurface oceans crusted over in frozen water ice, according to a new proposal at this year's American Astronomy Society Division for Planetary Sciences meeting in Provo, Utah. The hypothesis could explain the lack of signals from other technologically advanced civilizations, a conundrum known as the Fermi paradox.

#### Dao Angkan

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #28 on: 10/19/2017 10:35 PM »
It would be difficult for technological civilisations to evolve without fire.

#### redliox

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #29 on: 10/19/2017 10:57 PM »
It would be difficult for technological civilisations to evolve without fire.

Perhaps, but it could depend on the planet.  We have insects that build their homes instinctively and there are chemical fires (phosphorous I think) that can burn underwater without oxygen.  A planet rich in quartz or other minerals that refract and focus light could spur development of optics and perhaps primitive lasers.  The ways technology begins could be a varied as the way live evolves.

Why haven’t we had alien contact? Blame icy ocean worlds

Quote
Might ET be buried under too much ice to phone Earth? That’s what planetary scientist Alan Stern of the Southwest Research Institute in Boulder, Colorado, has concluded may be delaying our contact with alien civilizations. Most extraterrestrial creatures are likely deep inside their home planets, in subsurface oceans crusted over in frozen water ice, according to a new proposal at this year's American Astronomy Society Division for Planetary Sciences meeting in Provo, Utah. The hypothesis could explain the lack of signals from other technologically advanced civilizations, a conundrum known as the Fermi paradox.

Another example of how civilization might develop differently from us.
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#### topo334

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #30 on: 10/19/2017 11:03 PM »
How about the beings of xxauoin XXXXII, who worship the Jolly Green Giant and use a very large prime number as a key for decoding their frosty lore!

#### Phil Stooke

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #31 on: 10/19/2017 11:09 PM »
"Europeans went to America to grow potatoes and tobacco. "

Yikes, nobody picked up on this?  What about stealing gold?  Escaping persecution?   Establishing penal colonies?  Converting heathens?  There are lots of reasons people went to America and every one of them might find a parallel in alien visits to Earth, though none of them would look very good from our point of view.

And that leads to another suggestion about why we don't detect broadcasts - the aliens are afraid of what might happen if they announce their presence, so they are lurking and listening.

#### TakeOff

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #32 on: 10/20/2017 02:23 AM »
"Europeans went to America to grow potatoes and tobacco. "

Yikes, nobody picked up on this?  What about stealing gold?  Escaping persecution?   Establishing penal colonies?  Converting heathens?  There are lots of reasons people went to America and every one of them might find a parallel in alien visits to Earth, though none of them would look very good from our point of view.

And that leads to another suggestion about why we don't detect broadcasts - the aliens are afraid of what might happen if they announce their presence, so they are lurking and listening.
The natives were of no use. All of them just died from decease. Potatoes and tobacco was what was profitable. And later cotton slavery. If aliens don't smoke tobacco we have no reference as to what motivates them to move around in space. What motivation do virus have to help your immune system against other virus? Do you think that virus are "lurking and listening"? Do you imagine that they care about our existence at all? And most virus DNA is identical with sequences of our DNA. They are our identical twins. Alien life will be far different.

This whole subject suffers from Disneyfication as in talking cute cartoon animals. We can never have any kind of communication or relationship with any non-human being. We never have had even with the genetically almost identical life we have here on Earth, like grass or ants. Alien life is an astrophysical phenomena, not anything we can use our common sense to relate to. Even playing chess with a computer we ourselves have made is hopeless. Even AI cannot be dealt with by common sense. Common sense is only common among us.
« Last Edit: 10/20/2017 02:35 AM by TakeOff »

#### CuddlyRocket

##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #33 on: 10/20/2017 04:39 AM »
It would be difficult for technological civilisations to evolve without fire.

We don't know that. We know how we did it, and we used fire because we had fire. We haven't given much thought to the contra-factual!

#### Bynaus

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #34 on: 10/20/2017 06:03 AM »
If there was a 30 km thick ice ceiling over Earth - don't you think we would have punched through that centuries ago? Yeah, so do I. That explains nothing.

#### Star One

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #35 on: 10/20/2017 06:40 AM »
It would be difficult for technological civilisations to evolve without fire.

Perhaps, but it could depend on the planet.  We have insects that build their homes instinctively and there are chemical fires (phosphorous I think) that can burn underwater without oxygen.  A planet rich in quartz or other minerals that refract and focus light could spur development of optics and perhaps primitive lasers.  The ways technology begins could be a varied as the way live evolves.

Why haven’t we had alien contact? Blame icy ocean worlds

Quote
Might ET be buried under too much ice to phone Earth? That’s what planetary scientist Alan Stern of the Southwest Research Institute in Boulder, Colorado, has concluded may be delaying our contact with alien civilizations. Most extraterrestrial creatures are likely deep inside their home planets, in subsurface oceans crusted over in frozen water ice, according to a new proposal at this year's American Astronomy Society Division for Planetary Sciences meeting in Provo, Utah. The hypothesis could explain the lack of signals from other technologically advanced civilizations, a conundrum known as the Fermi paradox.

Another example of how civilization might develop differently from us.

As a side point I was slightly surprised this came from Alan Stern as I didn’t have him down as someone interested in this area of enquiry.

#### KelvinZero

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #36 on: 10/20/2017 12:06 PM »
I think you could still develop tool using intelligence without fire. Consider the octopus. You could also discover politics, probably a huge driver of intelligence. There would still be reasons to develop, agriculture, fortresses and weapons from materials such as bone.

Once you have a civilisation like that you have the scale for scientists. I think they would discover gasses, perhaps from volcanic vents or decaying organic matter. These could provide buoyancy to lift stones great distances. I think once you have competing nations and scientists everything gets figured out eventually.

After that, I think life under ice is a lot closer to becoming a space fairing species than us, if on a low gravity world like europa or Ceres. They could master space industrialisation without even leaving their planet or moon. Vehicles on the surface would allow fast travel. There would also likely be unique resources more available there.

For me, the more significant question is how much energy such an environment could provide, while not being so energetic as to lose all this ice and water to space. I heard somewhere is that Europa is not expected to have the energy to sustain more than very simple life.

#### Dao Angkan

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #37 on: 10/20/2017 07:42 PM »
I think you could still develop tool using intelligence without fire. Consider the octopus. You could also discover politics, probably a huge driver of intelligence. There would still be reasons to develop, agriculture, fortresses and weapons from materials such as bone.

Once you have a civilisation like that you have the scale for scientists. I think they would discover gasses, perhaps from volcanic vents or decaying organic matter. These could provide buoyancy to lift stones great distances. I think once you have competing nations and scientists everything gets figured out eventually.

After that, I think life under ice is a lot closer to becoming a space fairing species than us, if on a low gravity world like europa or Ceres. They could master space industrialisation without even leaving their planet or moon. Vehicles on the surface would allow fast travel. There would also likely be unique resources more available there.

For me, the more significant question is how much energy such an environment could provide, while not being so energetic as to lose all this ice and water to space. I heard somewhere is that Europa is not expected to have the energy to sustain more than very simple life.

I posted my brief response late last night, and was planning on elaborating after work today, but you've pretty much covered much of what I intended to say, even down to octopuses! Anyway, I'll expand on that a little bit.

The octopus shows us that underwater species can evolve intelligence and dexterity, and indeed evolve to use tools. I could certainly see such a creature evolving to human level intelligence and a neolithic level of technology. The extra difficulty that I see is the leap from a neolithic to a metallurgic civilisation. The human lineage used fire for various evolutionary benefits for over a million years before metallurgy was discovered, presumably as a by-product of the benefits that humans had evolved to control fire (heat treatment of flints). In an environment where fire isn't natural, then I think it's an extra filter of difficulty for evolution to head in that direction ... how would such a species discover metallurgy?

We can imagine various less likely scenarios, and as the universe is so vast, some of those may well have occurred, but it seems to me that it would be far more likelier to occur in an environment where fire occurs naturally.

As for basic microbial life? If it is ubiquitous where we find liquid water, then we can test that in our own solar system, but we can't really detect extra-solar biomarkers in sub-surface oceans, even if they outnumber surface oceans by whatever magnitude you care to choose.

Until we have more evidence, then I can see the appeal in the argument that microbial life may be far more common in sub-surface ocean ice worlds (as they are probably more common than temperate terrestrial worlds), but it doesn't answer the Fermi paradox. As already mentioned, if they are technologically advanced, then boring through a few kms of ice would be trivial, and as also already mentioned, most ice worlds have low gravity, so compared to us, space travel should be trivial too.

The Fermi paradox simply proposes that a single inter-stellar civilisation could populate the entire milky way in only a few million years, so in astronomical timescales they should be here already. Stay at home ice world civilisations doesn't solve the paradox, as Earth-like civilisations should already be here.
« Last Edit: 10/20/2017 07:52 PM by Dao Angkan »

#### eric z

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #38 on: 10/20/2017 07:46 PM »
I would respectfully disagree that politics is a driver of intelligence!

#### Dao Angkan

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #39 on: 10/20/2017 08:08 PM »
It would be difficult for technological civilisations to evolve without fire.

Perhaps, but it could depend on the planet.  We have insects that build their homes instinctively and there are chemical fires (phosphorous I think) that can burn underwater without oxygen.  A planet rich in quartz or other minerals that refract and focus light could spur development of optics and perhaps primitive lasers.  The ways technology begins could be a varied as the way live evolves.

Why haven’t we had alien contact? Blame icy ocean worlds

Quote
Might ET be buried under too much ice to phone Earth? That’s what planetary scientist Alan Stern of the Southwest Research Institute in Boulder, Colorado, has concluded may be delaying our contact with alien civilizations. Most extraterrestrial creatures are likely deep inside their home planets, in subsurface oceans crusted over in frozen water ice, according to a new proposal at this year's American Astronomy Society Division for Planetary Sciences meeting in Provo, Utah. The hypothesis could explain the lack of signals from other technologically advanced civilizations, a conundrum known as the Fermi paradox.

Another example of how civilization might develop differently from us.

As a side point I was slightly surprised this came from Alan Stern as I didn’t have him down as someone interested in this area of enquiry.

His expertise is ice worlds. Sub-surface liquid oceans are potential habitats for life. Ice worlds are probably more common than temperate terrestrial worlds. I don't think his analysis went any further than this.

Still, he has always personally responded to my questions about New Horizons in the past (admittedly quite a few years past), so I'm sure you'd get a response if you politely ask him about his opinion on this.
« Last Edit: 10/20/2017 08:14 PM by Dao Angkan »

#### Dao Angkan

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #40 on: 10/20/2017 08:41 PM »
I would respectfully disagree that politics is a driver of intelligence!

I know you say it in jest, but it was a good point ... something I hadn't considered before. Politics could well be a driver of evolution. Intelligence is extremely expensive, a bit like a peacock's feathers. In many species power is the main driver of sexual selection, and we even see that today, where physically old and unfit politicians in positions of power still have sexual relations with young, fit, and healthy members of the opposite sex who are attracted to them solely through power.

That's not a commentary on life, just an analysis on how intelligence could be sexually selected for, and how politics could potentially exaggerate that.

#### KelvinZero

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #41 on: 10/20/2017 11:15 PM »
I would respectfully disagree that politics is a driver of intelligence!

I know you say it in jest, but it was a good point ... something I hadn't considered before. Politics could well be a driver of evolution. Intelligence is extremely expensive, a bit like a peacock's feathers. In many species power is the main driver of sexual selection, and we even see that today, where physically old and unfit politicians in positions of power still have sexual relations with young, fit, and healthy members of the opposite sex who are attracted to them solely through power.

That's not a commentary on life, just an analysis on how intelligence could be sexually selected for, and how politics could potentially exaggerate that.
It isn't really my idea, just something I keep hearing. "Politics" might not be exactly the right word. I think for a while there was an almost-assumption that the evolution of intelligence was all about tool-making but I think that has gone out of favour.

https://en.wikipedia.org/wiki/Evolution_of_human_intelligence#Models

#### Dao Angkan

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #42 on: 10/21/2017 12:40 AM »
I would respectfully disagree that politics is a driver of intelligence!

I know you say it in jest, but it was a good point ... something I hadn't considered before. Politics could well be a driver of evolution. Intelligence is extremely expensive, a bit like a peacock's feathers. In many species power is the main driver of sexual selection, and we even see that today, where physically old and unfit politicians in positions of power still have sexual relations with young, fit, and healthy members of the opposite sex who are attracted to them solely through power.

That's not a commentary on life, just an analysis on how intelligence could be sexually selected for, and how politics could potentially exaggerate that.
It isn't really my idea, just something I keep hearing. "Politics" might not be exactly the right word. I think for a while there was an almost-assumption that the evolution of intelligence was all about tool-making but I think that has gone out of favour.

https://en.wikipedia.org/wiki/Evolution_of_human_intelligence#Models

Right, this is how I assume intelligence evolved in humans ... to cope with inter-social relations. What I hadn't previously considered was that evolution would favour those "best" at politics. It actually seems obvious now, any technologically advanced civilisation is likely to be "political", or at least hierarchical, as long as they have sexual selection.

Edit: So it might be wise to consider any E.T.s as being potentially deceptive, at least evolution would suggest that they may well be.
« Last Edit: 10/21/2017 12:59 AM by Dao Angkan »

#### DarkenedOne

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #43 on: 10/21/2017 02:19 AM »
Personally I doubt we will discover aliens by listening in our their communications.  There are a number of assumptions regarding extraterrestrial civilizations that the SETI approach is based on that are probably simply not true.

1. When they say broadcasting civilizations they do not mean civilizations like our own.  I did the calculation once to determine at what distance would we be able to detect a civilization just like our own.  Even for the large dishes like those in the Deep Space Network it turns out to be less than one light year.  The assumption SETI makes is that advanced civilizations will be broadcasting signals millions of times more powerful than signals we broadcast.

2.  The next assumption is that aliens would be using broadcasts for communication in the first place.  Broadcasting is an incredibly inefficient method of communication.  If you any idea as to where your target is then you will send a directed signal to that target.  Our communications system has gotten more and more efficient by sending data in narrower and narrower beams.  Narrower beams drives you toward higher frequencies.   Higher frequencies also allow you to communicate more data.  That is the fundamental reason why you see our communication systems moving up the EM spectrum over time.  This leads to the third major assumption.

3.   It is highly unlikely that aliens would be using radio waves to communicate at all.  They are enormously inefficient at interstellar distances.  Given how we have been moving up the EM spectrum to achieve greater efficiency in our communications we can safely assume that more advanced civilizations have already gone through this evolution.  They are probably using something like gamma ray lasers to communicate.  They might even have something even better based on physics that we do not understand yet.
With that I will leave you with this image.

#### Star One

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #44 on: 11/02/2017 07:18 PM »
Aliens may be more like us than we think

Quote
Hollywood films and science fiction literature fuel the belief that aliens are monster-like beings, who are very different to humans. But new research suggests that we could have more in common with our extra-terrestrial neighbours, than initially thought.

In a new study published in the International Journal of Astrobiology scientists from the University of Oxford show for the first time how evolutionary theory can be used to support alien predictions and better understand their behaviour. They show that aliens are potentially shaped by the same processes and mechanisms that shaped humans, such as natural selection.

The theory supports the argument that foreign life forms undergo natural selection, and are like us, evolving to be fitter and stronger over time.

Sam Levin, a researcher in Oxford’s Department of Zoology, said: ‘A fundamental task for astrobiologists (those who study life in the cosmos) is thinking about what extra-terrestrial life might be like. But making predictions about aliens is hard. We only have one example of life - life on Earth -- to extrapolate from. Past approaches in the field of astrobiology have been largely mechanistic, taking what we see on Earth, and what we know about chemistry, geology, and physics to make predictions about aliens.

http://www.ox.ac.uk/news/2017-10-31-aliens-may-be-more-us-we-think#

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #45 on: 11/06/2017 02:39 PM »
If an emissary from an extraterrestrial civilization came to Earth and wanted to remain incognito while observing our progress towards the stars, what cover would it choose?

Running a website dedicated to exploration of outer space would not be the worst way to collect intelligence, for evaluation and scheduled reports to send "home".

#### QuantumG

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #46 on: 11/07/2017 02:51 AM »
If an emissary from an extraterrestrial civilization came to Earth and wanted to remain incognito while observing our progress towards the stars, what cover would it choose?

Running a website dedicated to exploration of outer space would not be the worst way to collect intelligence, for evaluation and scheduled reports to send "home".

Well, I'm pretty sure Chris has been to New York, but he didn't overstay his visa waiver... I don't think.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

#### Star One

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #47 on: 11/08/2017 07:38 PM »
What Happens If China Makes First Contact?

As America has turned away from searching for extraterrestrial intelligence, China has built the world’s largest radio dish for precisely that purpose.

https://www.theatlantic.com/magazine/archive/2017/12/what-happens-if-china-makes-first-contact/544131/

#### Alpha_Centauri

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« Reply #48 on: 11/09/2017 12:16 AM »
Doesn't matter, all the aliens I've seen speak English.

#### cosmicvoid

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« Reply #49 on: 11/10/2017 11:37 PM »
Doesn't matter, all the aliens I've seen speak English.

Except for the ones in Arrival (2106), they speak in circles.
Infiinity or bust.

#### Lar

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« Reply #50 on: 11/11/2017 11:41 AM »
Doesn't matter, all the aliens I've seen speak English.

Except for the ones in Arrival (2106), they speak in circles.

Not to spoil the plot of that movie if you haven't seen it[1] but I don't think there's a sequel in 2106

1 - anyone interested in aliens, language, or diplomacy should see it.
« Last Edit: 11/11/2017 11:46 AM by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

#### Star One

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« Reply #51 on: 11/11/2017 07:52 PM »
Doesn't matter, all the aliens I've seen speak English.

Except for the ones in Arrival (2106), they speak in circles.

Yeah thanks for ruining the film for me with your inconsiderate post.

#### Lar

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« Reply #52 on: 11/12/2017 12:10 AM »
Doesn't matter, all the aliens I've seen speak English.

Except for the ones in Arrival (2106), they speak in circles.

Yeah thanks for ruining the film for me with your inconsiderate post.
Seriously?
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

#### QuantumG

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« Reply #53 on: 11/12/2017 12:17 AM »
Yeah thanks for ruining the film for me with your inconsiderate post.
Seriously?

You're history's greatest monster.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

#### vapour_nudge

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« Reply #54 on: 11/12/2017 12:25 AM »
I watched that last week. If someone pays you to watch that movie, you're being ripped off.

#### Lar

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« Reply #55 on: 11/12/2017 12:48 AM »
I watched that last week. If someone pays you to watch that movie, you're being ripped off.

We're a bit off topic (and maybe we start a thread for it?) but I have to disagree. I found it very entrancing, well made, thought provoking and a thoroughly great movie. Rotten Tomatoes agrees, as do many critics, some going so far as to say it was 2016's best movie. It's not blasters and explosions, it is very cerebral. But worth your attention. (and I liked Passengers too so ...)

YMMV.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

#### Star One

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« Reply #56 on: 11/12/2017 08:35 AM »
Yeah thanks for ruining the film for me with your inconsiderate post.
Seriously?

You're history's greatest monster.

Just for the sake of clarity not everyone can see a film straightaway as it usually takes a while for a film to get onto terrestrial TV over here in the UK. I do have Netflix but it’s not on the UK schedule and I also have SKY satellite but not the film channels due to cost. But that said it was a bit of a silly comment I suppose by me.
« Last Edit: 11/12/2017 08:40 AM by Star One »

#### vapour_nudge

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« Reply #57 on: 11/12/2017 08:53 AM »
I liked Passengers too. My wife liked it too. But we both fell asleep watching Arrival. I understand that not everyone would feel the same.  Anyway back on topic. Sorry all

#### John Santos

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« Reply #58 on: 11/12/2017 09:41 AM »
Yeah thanks for ruining the film for me with your inconsiderate post.
Seriously?

You're history's greatest monster.

Just for the sake of clarity not everyone can see a film straightaway as it usually takes a while for a film to get onto terrestrial TV over here in the UK. I do have Netflix but it’s not on the UK schedule and I also have SKY satellite but not the film channels due to cost. But that said it was a bit of a silly comment I suppose by me.
You probably didn't notice the typo (since trimmed) in the original post.  Unless you're a time-travelling alien.

#### Star One

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« Reply #59 on: 11/12/2017 10:04 AM »
Yeah thanks for ruining the film for me with your inconsiderate post.
Seriously?

You're history's greatest monster.

Just for the sake of clarity not everyone can see a film straightaway as it usually takes a while for a film to get onto terrestrial TV over here in the UK. I do have Netflix but it’s not on the UK schedule and I also have SKY satellite but not the film channels due to cost. But that said it was a bit of a silly comment I suppose by me.
You probably didn't notice the typo (since trimmed) in the original post.  Unless you're a time-travelling alien.

I am sticking to blaming my iPhone which seems to have issues with its spell correct.

#### Star One

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« Reply #60 on: 11/16/2017 07:49 PM »

#### Dao Angkan

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« Reply #61 on: 11/16/2017 07:57 PM »
Is it ethical to transmit powerful radio signals?

I'll answer that, any civilisation capable of being a threat to us should already know that we're here and have already come and sterilised the planet. As for the question of who on Earth should have the responsibility of contacting them, by the time that we get a reply back, then the people (and governments, countries etc) who originally sent the message will be long gone.
« Last Edit: 11/16/2017 08:06 PM by Dao Angkan »

#### Johnnyhinbos

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« Reply #62 on: 11/16/2017 09:05 PM »
Is it ethical to transmit powerful radio signals?

I'll answer that, any civilisation capable of being a threat to us should already know that we're here and have already come and sterilised the planet. As for the question of who on Earth should have the responsibility of contacting them, by the time that we get a reply back, then the people (and governments, countries etc) who originally sent the message will be long gone.
I don't agree with that sentiment. Any civilization that has made it far enough along it's development to not have wiped itself out of existence is one that has matured enough to have developed a set of mature morality and ethical codes. Therefore I highly doubt it would sterilize another sentient species. Quarantined on the other hand...
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#### Dao Angkan

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« Reply #63 on: 11/16/2017 09:25 PM »
I should reword that as "who might consider us as a threat". Still, they may well have developed moral and ethical codes, ones that say that allowing any other species to evolve far enough to potentially threaten their existence would be morally and ethically wrong (to their own species). In which case, the logical course of action would be to sterilise any world which could potentially evolve threatening species.

Edit: I'll note our species eradication of infectious diseases as an example of a species considering it moral and ethical to eradicate potential threats to themselves.

If you're only sterilising cyanobacteria, is it unethical?
« Last Edit: 11/16/2017 09:43 PM by Dao Angkan »

#### Johnnyhinbos

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« Reply #64 on: 11/16/2017 10:59 PM »
I’ll bite - as I work around and with aquatic species for a living. We catch live crabs in Boston Harbor as feedstock for exhibit animals. However we aren’t allowed to put these crabs in exhibit to feed to large puffers etc because our Animal Care and Use Committee forbids it. Instead we have to euthanize the crabs in a two phase process that is pain free and humane to the crab. And before people say crabs can’t feel pain or have the brain capacity for complex emotions - wrong (summoning the inner Jim).

Recent studies show inverts such as crabs have opioid receptors which strongly suggests sensation of pain. This is as opposed to nociception. Crabs have also amazingly shown the ability to have emotions. (I can quote scientific papers on this subject if desired).

Point being? Even us lowly developed Homo sapien have evolved to learn right from wrong, even when it involves a completely alien species as compared to our own.

Just ask any scientist involved with planetary protection...
« Last Edit: 11/16/2017 11:06 PM by Johnnyhinbos »
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#### Dalhousie

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« Reply #65 on: 11/17/2017 12:06 AM »
I watched that last week. If someone pays you to watch that movie, you're being ripped off.

What?  I thought it was one of the best and most thought provoking SF films for many years.
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#### Dalhousie

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##### Re: Why We’ll Have Evidence of Aliens—If They Exist—By 2035
« Reply #66 on: 11/17/2017 12:09 AM »
What Happens If China Makes First Contact?

As America has turned away from searching for extraterrestrial intelligence, China has built the world’s largest radio dish for precisely that purpose.

https://www.theatlantic.com/magazine/archive/2017/12/what-happens-if-china-makes-first-contact/544131/

See Three Body Problem for an excellent perspective by a Chinese novel about this.  Probably the best SF novel I have read in the past 12 months.  Perhaps longer.
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#### Star One

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« Reply #67 on: 11/17/2017 07:12 PM »
Phoning E.T.: Message Sent to Nearby Planet That Could Host Life

Quote
Last month, scientists and artists beamed a message to GJ 273, a red dwarf also known as Luyten's star that lies 12.36 light-years from Earth, project team members revealed today (Nov. 16). Luyten's star hosts two known planets, one of which, GJ 273b, may be capable of supporting life as we know it.

Though the message was designed to provoke a response from the hypothetical denizens of GJ 273b, the main goal in sending the communication involved laying a foundation for the future, said team member Douglas Vakoch, president of METI (Messaging Extraterrestrial Intelligence) International, a San Francisco-based nonprofit. [13 Ways to Hunt Intelligent Aliens]

https://amp.space.com/38803-meti-signal-beamed-habitable-alien-planet.html

#### hop

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« Reply #68 on: 11/17/2017 09:00 PM »
I should reword that as "who might consider us as a threat".
Yeah, this has always been my objection to the paranoia about transmitting signals.

It's hard to imagine a civilization that has the technological capability and motivation to come wipe us out but not passively detect the fact that Earth harbors life.

We would have a good chance of detecting biosignatures around nearby stars with current technology if we put serious budget behind it. We are nowhere close to being able to reach other star systems, let alone sterilizing whole planets when we get there.

Any civilization that can send substantial payloads between star systems isn't going to have trouble building, say 100 meter space telescopes.

#### Dao Angkan

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« Reply #69 on: 11/17/2017 09:07 PM »
I’ll bite - as I work around and with aquatic species for a living. We catch live crabs in Boston Harbor as feedstock for exhibit animals. However we aren’t allowed to put these crabs in exhibit to feed to large puffers etc because our Animal Care and Use Committee forbids it. Instead we have to euthanize the crabs in a two phase process that is pain free and humane to the crab. And before people say crabs can’t feel pain or have the brain capacity for complex emotions - wrong (summoning the inner Jim).

Recent studies show inverts such as crabs have opioid receptors which strongly suggests sensation of pain. This is as opposed to nociception. Crabs have also amazingly shown the ability to have emotions. (I can quote scientific papers on this subject if desired).

Point being? Even us lowly developed Homo sapien have evolved to learn right from wrong, even when it involves a completely alien species as compared to our own.

Just ask any scientist involved with planetary protection...

Catching wild animals in order to kill them and feed them to other captured animals which are then displayed as an exhibit for a more intelligent species to observe only shows that what crabs might consider right and wrong is quite a bit different than what people "who work around and with aquatic species for a living" consider right and wrong, especially when they consider their "feedstock" to have emotions.
« Last Edit: 11/17/2017 09:24 PM by Dao Angkan »

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« Reply #70 on: 11/17/2017 09:34 PM »
by the time that we get a reply back, then the people (and governments, countries etc) who originally sent the message will be long gone.
The best way to eliminate the wait time for a reply to arrive is to send yourself with your first message. Encode your entire genome and phenome plus your memories up to today. Include instructions for building you from the data. Make persuasive case that you are harmless and could not hurt a fly.

#### Dao Angkan

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« Reply #71 on: 11/18/2017 10:38 PM »
by the time that we get a reply back, then the people (and governments, countries etc) who originally sent the message will be long gone.
The best way to eliminate the wait time for a reply to arrive is to send yourself with your first message. Encode your entire genome and phenome plus your memories up to today. Include instructions for building you from the data. Make persuasive case that you are harmless and could not hurt a fly.

It's an interesting proposition, we'd still have to wait for a reply, but the "clone" could converse rather than waiting for a reply from Earth after every correspondence. Maybe an easier way would be to just send an AI? The AI discusses matters that humans are interested in and sends it back to Earth, whilst sharing allowed information with the aliens immediately.

Edit: This could be a basis for inter-stellar trade. The AI could receive data from Earth, such as scientific discoveries, or even something as mundane as the latest soap opera. The AI then trades that data for data that might have value on Earth (scientific discoveries / soaps etc).
« Last Edit: 11/18/2017 10:46 PM by Dao Angkan »

#### Star One

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« Reply #72 on: 12/31/2017 12:01 PM »
What is 'Zoo Theory'?

Quote
Aliens exist, but they are hiding and purposefully trying to avoid contact with humans, says the "Zoo Theory". The thesis is an attempt to explain why humans have yet to meet or interact with intelligent life outside the planet.

The theory, proposed by MIT radio astronomer John A. Ball, says that aliens out there are smarter than humans, but not yet powerful enough to take over the universe, so they monitor human activity from afar. Ball explains that they are curious enough to stop by once in a while, and that is why there are so many sightings of UFOs and alien crafts, reports the Science Examiner (SE).

http://www.ibtimes.co.uk/what-zoo-theory-bizarre-thesis-attempts-explain-why-aliens-are-yet-contact-us-1653220

Here’s the paper itself.

https://www.haystack.mit.edu/hay/staff/jball/etiy.pdf

#### redliox

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« Reply #73 on: 12/31/2017 03:36 PM »
What is 'Zoo Theory'?

Quote
Aliens exist, but they are hiding and purposefully trying to avoid contact with humans, says the "Zoo Theory". The thesis is an attempt to explain why humans have yet to meet or interact with intelligent life outside the planet.

I think there are 2 possibilities we can look too, with "Zoo Theory" being one of them.  The other would be that space (or specifically interstellar) travel is extremely hard.  Then again our instruments might be considered "short ranged" but neither are we blind.
"Let the trails lead where they may, I will follow."
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« Reply #74 on: 12/31/2017 07:35 PM »
Vol. 2 The Dark Forest in Liu Cixin's Three-Body trilogy explores the Zoo hypothesis.

#### Star One

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« Reply #75 on: 12/31/2017 08:21 PM »
What is 'Zoo Theory'?

Quote
Aliens exist, but they are hiding and purposefully trying to avoid contact with humans, says the "Zoo Theory". The thesis is an attempt to explain why humans have yet to meet or interact with intelligent life outside the planet.

I think there are 2 possibilities we can look too, with "Zoo Theory" being one of them.  The other would be that space (or specifically interstellar) travel is extremely hard.  Then again our instruments might be considered "short ranged" but neither are we blind.

I will put my cards on the deck by saying I believe Zoo Theory is the answer to the seeming galactic silence. That we are observed from afar but deemed far too primitive to communicate with.

#### vapour_nudge

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« Reply #76 on: 12/31/2017 09:19 PM »
What is 'Zoo Theory'?

Quote
Aliens exist, but they are hiding and purposefully trying to avoid contact with humans, says the "Zoo Theory". The thesis is an attempt to explain why humans have yet to meet or interact with intelligent life outside the planet.

I think there are 2 possibilities we can look too, with "Zoo Theory" being one of them.  The other would be that space (or specifically interstellar) travel is extremely hard.  Then again our instruments might be considered "short ranged" but neither are we blind.

I will put my cards on the deck by saying I believe Zoo Theory is the answer to the seeming galactic silence. That we are observed from afar but deemed far too primitive to communicate with.
Isn’t that just an easy way to explain away the fact that there is no ET? It is like saying that the proof they are out there is that we can’t see them and have had no contact? How could it be justified to look for them if they won’t let us see them?
« Last Edit: 12/31/2017 09:20 PM by vapour_nudge »

#### Star One

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« Reply #77 on: 12/31/2017 10:52 PM »
What is 'Zoo Theory'?

Quote
Aliens exist, but they are hiding and purposefully trying to avoid contact with humans, says the "Zoo Theory". The thesis is an attempt to explain why humans have yet to meet or interact with intelligent life outside the planet.

I think there are 2 possibilities we can look too, with "Zoo Theory" being one of them.  The other would be that space (or specifically interstellar) travel is extremely hard.  Then again our instruments might be considered "short ranged" but neither are we blind.

I will put my cards on the deck by saying I believe Zoo Theory is the answer to the seeming galactic silence. That we are observed from afar but deemed far too primitive to communicate with.
Isn’t that just an easy way to explain away the fact that there is no ET? It is like saying that the proof they are out there is that we can’t see them and have had no contact? How could it be justified to look for them if they won’t let us see them?

Why should we expect an alien intelligence to behave in any way to accommodate us, especially if to them we aren’t worth communicating with?

#### vapour_nudge

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« Reply #78 on: 12/31/2017 11:12 PM »
It’s circular.
Don’t you at least see the irony in what this theory is suggesting? Explain away the reason why there are no aliens by saying they are hiding from us. It seems like a means for perpetual funding & justification of the (non) science of SETI

HNY to you nonetheless
« Last Edit: 12/31/2017 11:13 PM by vapour_nudge »

#### Star One

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« Reply #79 on: 01/01/2018 08:21 AM »
It’s circular.
Don’t you at least see the irony in what this theory is suggesting? Explain away the reason why there are no aliens by saying they are hiding from us. It seems like a means for perpetual funding & justification of the (non) science of SETI

HNY to you nonetheless

Of course it’s circular. Reality is often imperfect.

HNY

#### dror

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« Reply #80 on: 01/01/2018 03:03 PM »
What is 'Zoo Theory'?

Quote
Aliens exist, but they are hiding and purposefully trying to avoid contact with humans, says the "Zoo Theory". The thesis is an attempt to explain why humans have yet to meet or interact with intelligent life outside the planet.

I think there are 2 possibilities we can look too, with "Zoo Theory" being one of them.  The other would be that space (or specifically interstellar) travel is extremely hard.  Then again our instruments might be considered "short ranged" but neither are we blind.

I will put my cards on the deck by saying I believe Zoo Theory is the answer to the seeming galactic silence. That we are observed from afar but deemed far too primitive to communicate with.
You used the correct term there since supporting such a theory is no different than any other religions beliefe.
The lack of evidence can support whatever crazy idea you can think of. You might as well belive that the aliens are shy or that they are tiny or godlike. Whatever .
"If we crave some cosmic purpose, then let us find ourselves a worthy goal. "
Carl Sagan, Pale Blue Dot

#### the_other_Doug

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« Reply #81 on: 01/01/2018 03:15 PM »
It’s circular.
Don’t you at least see the irony in what this theory is suggesting? Explain away the reason why there are no aliens by saying they are hiding from us. It seems like a means for perpetual funding & justification of the (non) science of SETI

HNY to you nonetheless

Of course it’s circular. Reality is often imperfect.

HNY

I'm not sure you understood what he meant.  He was saying you are using a circular argument.  It goes as follows:

...
#1:  "We've looked!  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"

THAT is circular logic.  By definition, it cannot prove anything.  All it can do is attempt the impossible task of proving a negative, which just gets you into a circular argument...

The world being imperfect has nothing to do with applying circular logic.  The person applying the circular logic is the imperfect portion of this calculation, I hate to say...
-Doug  (With my shield, not yet upon it)

#### Star One

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« Reply #82 on: 01/01/2018 03:59 PM »
It’s circular.
Don’t you at least see the irony in what this theory is suggesting? Explain away the reason why there are no aliens by saying they are hiding from us. It seems like a means for perpetual funding & justification of the (non) science of SETI

HNY to you nonetheless

Of course it’s circular. Reality is often imperfect.

HNY

I'm not sure you understood what he meant.  He was saying you are using a circular argument.  It goes as follows:

...
#1:  "We've looked!  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"
#2:  "They must be hiding!  Look harder!"
#1:  "We looked harder.  We can't find them!"

THAT is circular logic.  By definition, it cannot prove anything.  All it can do is attempt the impossible task of proving a negative, which just gets you into a circular argument...

The world being imperfect has nothing to do with applying circular logic.  The person applying the circular logic is the imperfect portion of this calculation, I hate to say...

I tell you what rather than sneering at my honesty in at least declaring a position on this. Why don’t some of you be less cowardly and actually declare a position. Shouting from the sidelines has always been a lot easier than actually taking part.

No wonder people from SETI don’t stick their heads above the parapet when the people in the peanut galleries are too busy throwing peanuts.
« Last Edit: 01/01/2018 04:02 PM by Star One »

#### RotoSequence

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« Reply #83 on: 01/01/2018 07:59 PM »
THAT is circular logic.  By definition, it cannot prove anything.  All it can do is attempt the impossible task of proving a negative, which just gets you into a circular argument...

The world being imperfect has nothing to do with applying circular logic.  The person applying the circular logic is the imperfect portion of this calculation, I hate to say...

We don't have a circular logic problem. We have a seemingly reasonable assertion, and missing evidence - much like the dark days of Exoplanetology (the Sun is one of countless stars in the universe, therefor there must be countless planets - but we haven't found any).

Absence of evidence is not evidence of absence, but we still haven't seen any aliens. There are two forks in the road to resolving this conundrum:

One, we're not looking hard enough, because barring exceptionalism, the Earth is one of countless planets in the universe, and it has life on it; therefor, we can't be alone out there.

Two, absence of evidence is evidence of absence, and thus, through logical fallacy, we are clearly alone in the universe.
« Last Edit: 01/01/2018 08:09 PM by RotoSequence »

#### mme

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« Reply #84 on: 01/01/2018 08:25 PM »
It’s circular.
Don’t you at least see the irony in what this theory is suggesting? Explain away the reason why there are no aliens by saying they are hiding from us. It seems like a means for perpetual funding & justification of the (non) science of SETI

HNY to you nonetheless
My understanding is that SETI is not government funded, Senator Richard Bryan saw to that. In my mind the Zoo Hypothesis presumes too much, but that does not invalidate curiosity about the possibility of other intelligent life in the universe.
Space is not Highlander.  There can, and will, be more than one.

#### Star One

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« Reply #85 on: 01/01/2018 10:04 PM »
THAT is circular logic.  By definition, it cannot prove anything.  All it can do is attempt the impossible task of proving a negative, which just gets you into a circular argument...

The world being imperfect has nothing to do with applying circular logic.  The person applying the circular logic is the imperfect portion of this calculation, I hate to say...

We don't have a circular logic problem. We have a seemingly reasonable assertion, and missing evidence - much like the dark days of Exoplanetology (the Sun is one of countless stars in the universe, therefor there must be countless planets - but we haven't found any).

Absence of evidence is not evidence of absence, but we still haven't seen any aliens. There are two forks in the road to resolving this conundrum:

One, we're not looking hard enough, because barring exceptionalism, the Earth is one of countless planets in the universe, and it has life on it; therefor, we can't be alone out there.

Two, absence of evidence is evidence of absence, and thus, through logical fallacy, we are clearly alone in the universe.

It’s possible that if things like Neutron Star mergers are far more common than theorised that much of the universe has been sterilised of life. And we are just lucky for now.

#### the_other_Doug

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« Reply #86 on: 01/01/2018 10:21 PM »
I tell you what rather than sneering at my honesty in at least declaring a position on this. Why don’t some of you be less cowardly and actually declare a position. Shouting from the sidelines has always been a lot easier than actually taking part.

No wonder people from SETI don’t stick their heads above the parapet when the people in the peanut galleries are too busy throwing peanuts.

I will tell you my position, as I have in the past.

Belief is nothing.  Proof is everything.

It sounds to me like you don't believe that is taking a position.  If you can't tell what position I am taking, that's your problem, not mine.
-Doug  (With my shield, not yet upon it)

#### Star One

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« Reply #87 on: 01/01/2018 10:55 PM »
I tell you what rather than sneering at my honesty in at least declaring a position on this. Why don’t some of you be less cowardly and actually declare a position. Shouting from the sidelines has always been a lot easier than actually taking part.

No wonder people from SETI don’t stick their heads above the parapet when the people in the peanut galleries are too busy throwing peanuts.

I will tell you my position, as I have in the past.

Belief is nothing.  Proof is everything.

It sounds to me like you don't believe that is taking a position.  If you can't tell what position I am taking, that's your problem, not mine.

Because that position is a facile one of hiding behind a position that makes it sound like a  allegory for religious belief, when it’s nothing of the sort. If you’re incapable of seeing why it isn’t that’s not my problem.
« Last Edit: 01/01/2018 11:03 PM by Star One »

#### the_other_Doug

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« Reply #88 on: 01/02/2018 12:01 AM »
"Belief is nothing.  Proof is everything"  That is as succinctly as I could phrase the basis of the scientific method.

The fact that you keep claiming the scientific method is "facile" just because it requires proof before acceptance weakens your position incredibly.  As much as there is a lot of room for rational discussion in this area, it simply becomes absurd when the scientific method is seen as the wrong way of looking at the issue.
-Doug  (With my shield, not yet upon it)

#### Star One

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« Reply #89 on: 01/02/2018 10:37 AM »
"Belief is nothing.  Proof is everything"  That is as succinctly as I could phrase the basis of the scientific method.

The fact that you keep claiming the scientific method is "facile" just because it requires proof before acceptance weakens your position incredibly.  As much as there is a lot of room for rational discussion in this area, it simply becomes absurd when the scientific method is seen as the wrong way of looking at the issue.

Where have I said the scientific method is facile. What I am saying is facile is your personal interpretation of zoo theory, and your general understanding of this topic with your ridiculous comparison of SETI to a religion.
« Last Edit: 01/02/2018 10:40 AM by Star One »

#### sghill

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« Reply #90 on: 01/02/2018 11:57 AM »
Bring the thunder Elon!

#### RotoSequence

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« Reply #91 on: 01/02/2018 12:11 PM »
Man alive I am terrible at inductive reasoning in the morning

It remains inconceivable to many people that humans could be alone in the universe. Our searches, to date, have investigated a tiny fraction of all the possible places to look.

We'll find them, or we won't. In the grand scheme of things, we haven't looked very hard at all yet!
« Last Edit: 01/02/2018 12:12 PM by RotoSequence »

#### tea monster

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« Reply #92 on: 01/02/2018 12:47 PM »
We've barely looked at all. If we build a large enough space telescope, we can run the spectra of nearby worlds to check for oxygen, nitrogen, methane, etc. That will give us something more conclusive as to what the state of play is in the local area for earthlike planets, and possibly, life itself.

As to intelligent life, it could be that they are using a different method of communication to ourselves that we have yet to master. We could be like a South Sea Islander, climbing to the top of his atoll with a conch shell to his ear, listening for signs of life, while radio waves from cities on the other side of the globe course through and around him.

#### Star One

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« Reply #93 on: 01/05/2018 10:54 PM »
Man alive I am terrible at inductive reasoning in the morning

It remains inconceivable to many people that humans could be alone in the universe. Our searches, to date, have investigated a tiny fraction of all the possible places to look.

We'll find them, or we won't. In the grand scheme of things, we haven't looked very hard at all yet!

Well with two trillion galaxies in the universe there’s a lot of places to look

#### Star One

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« Reply #94 on: 01/07/2018 08:13 PM »
Further to the above there’s no need for faith in believing in a reasonable chance for other intelligent life you only have to rely on the maths of probability and the sheer number of galaxies, stars, planets and probably moons out there.
« Last Edit: 01/07/2018 08:14 PM by Star One »

#### M.E.T.

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« Reply #95 on: 01/07/2018 10:01 PM »
Further to the above there’s no need for faith in believing in a reasonable chance for other intelligent life you only have to rely on the maths of probability and the sheer number of galaxies, stars, planets and probably moons out there.

Isn't that just the Drake equation paraphrased without the detail? And since the probabilities of a number of the variables in the Drake equation are frankly unknown to us at this point, it is not that difficult to get a result of "1" intelligent civilization, by just playing with one or two of the numbers.

I happen to believe in a version of the Rare Earth Hypothesis. I think Earth is far more special than the adherents of the mediocrity principle would like to accept. Whether it is rare enough to result in an answer of "1" to the Drake equation, that I can't say. But an answer of 1 per galaxy, or 1 every hundred or thousand or million galaxies, is certainly not impossible.

In which case the closest intelligent civilization might be millions of light years away, in a galaxy far, far away.
« Last Edit: 01/07/2018 10:02 PM by M.E.T. »

#### Star One

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« Reply #96 on: 01/07/2018 10:11 PM »
Further to the above there’s no need for faith in believing in a reasonable chance for other intelligent life you only have to rely on the maths of probability and the sheer number of galaxies, stars, planets and probably moons out there.

Isn't that just the Drake equation paraphrased without the detail? And since the probabilities of a number of the variables in the Drake equation are frankly unknown to us at this point, it is not that difficult to get a result of "1" intelligent civilization, by just playing with one or two of the numbers.

I happen to believe in a version of the Rare Earth Hypothesis. I think Earth is far more special than the adherents of the mediocrity principle would like to accept. Whether it is rare enough to result in an answer of "1" to the Drake equation, that I can't say. But an answer of 1 per galaxy, or 1 every hundred or thousand or million galaxies, is certainly not impossible.

In which case the closest intelligent civilization might be millions of light years away, in a galaxy far, far away.

The problem with rare Earth theory is it assumes that to get intelligent life you have to have a planet like the Earth. I think it says more about the arrogance of our own belief that somehow we are unique than anything useful about the actual reality of the universe. It’s more probable that life occurs in a great variety of different conditions.

The problem with humans is we expect to find things similar to us when there’s no evidence that other intelligent life would be anything at all like us. Using one data point as a basis to extrapolate a way of looking for life is a rubbish way of going about things when you think about it. And probably why we will continue to struggle to find life.
« Last Edit: 01/07/2018 10:13 PM by Star One »

#### RotoSequence

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« Reply #97 on: 01/07/2018 10:48 PM »
About five billion species are estimated to have existed on Earth at some point in time. Our current evidence shows that only one species has created technology and civilization. Life in the universe may be relatively common, but our own data shows that intelligence and civilization are a rather uncommon occurrence. This is one of the terms in the Drake Equation, the odds have to be spectacularly low for us humans to be truly alone in the universe. "Too far away to ever detect another civilization?" That's not an unrealistic outcome.

#### deruch

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« Reply #98 on: 01/08/2018 02:25 AM »
Bringing over from the Boyajian's star thread:
The hubris is strong with the anti-ETI crowd again I see.
If thinking the universe can do weird, unexpected stuff without aliens is hubris... guilty

In seriousness though, I'm not "anti-ET". I'm firmly in the camp that says we aren't special, they are probably out there and we should keep our eyes and minds open. However, in the history of astronomy a lot more stuff that started out as weird and unexplained turned out to be dust than aliens. Absent specific data pointing to ET, I'll continue to expect most astronomical puzzles to have natural explanations. (edit for emphasis: This doesn't mean we shouldn't look, it just means we shouldn't be surprised if it turns out to be natural)

For this star, I've never seen anything that specifically favors of ET. It's weird and unexplained, sure, but nothing about the weirdness favors an artificial origin. If the light curve matched simple geometric shapes or blinked out prime numbers or something like that it would be different story, but in reality it looks like the kind of chaotic noisy stuff nature does all the time.

IMO the whole perception that it might be aliens mostly stemmed from misunderstanding. Wright's original mega-structure paper that kicked the hype off basically asked "Does this unexplained light curve fit ideas about what advanced aliens could build?" and concluded didn't fit particularly well, though limited data and the flexibility of "aliens" prevents ruling them out. Unfortunately in the press and popular opinion "astronomer examines whether it could be aliens" turned into "astronomers think it could be aliens!"
No need to be"anti ET"...  Just need to require specific evidence
.

Current ET arguments are "by elimination". They say that since there isn't a simple conclusive natural explanation yet, and if we tailor a sufficiently advanced alien capability around the observation, then we have a credible case for ET.

This kind of logic can be used to "explain" anything in the universe, and can be equally "successful" in arguing for all sorts of gods as well.  "It's too complex to have occured naturally".

I personally would want extraordinary evidence for the existence of specific aliens, not just an observation that's hard to explain.

Why would you require extraordinary evidence?

I’d thought you’d need the same level of evidence as any other natural phenomena, unless somehow you don’t think other intelligent life is a natural development in the universe.

You can’t just move around the goalposts to suit yourself.

IMO, 3 reasons to want extraordinary evidence.  First, is due to prior plausibility.  While I think that the general plausibility for there to be other ETI elsewhere in the Universe is fairly high, the plausibility that it is responsible for any particular new signal/observation is very, very low.  This is mostly a function of our general ignorance of the Universe and how everything in it works.  For all we have learned, we still just don't know that much.  Which means that we are all the time discovering new natural phenomena and as a result, the likelihood that any new observation is a result of a natural phenomenon is quite high.  This boils down to, If you hear hoofbeats, think horses not zebras.  Which is good advice unless you happen to be on the African Savanna.  We know that the dispersion/density of any advanced ET in the universe is not high enough to make their presence trivially obvious in our region of space.  So, as far as we can tell, we're not in the Serengeti.  Ergo, while still possible, zebras remain a bad first guess.

The second reason is that arguments for ET causing some specific phenomenon are, as meekgee pointed out, by elimination (based on our ignorance) and generally tend to border on being unfalsifiable.  Since a sufficiently advanced technology is essentially indistinguishable from magic to us (paraphrasing Clarke), ETs can have "magic" powers to overcome any challenge.  It reminds me of discussing radiometric dating with a Christian who claims the world is only 6,000 years old.  Their argument eventually reverts to, Well, God has the power to arbitrarily alter the ratios of elements/isotropes in a way that would mislead us or He can arbitrarily change the length of half-lives so that we get the wrong answer.  Which, I suppose, is true if there is such a God but I have no reason to believe it to have actually happened regardless of God's existence.  In this discussion, ET causes remain possible but why a civilization capable of affecting X, and causing Y phenomenon should only be noticeable by this one mechanism usually relies on special pleading.

Third is that humans are biological chauvanists.  We seem to have an innate desire to see ourselves in everything else.  We anthropomorphize pretty much everything.  We do it in religion.  When we study other animals.  Heck, even in astronomy.  Just look at the discovery of canals on Mars.  This tendency's distortive effects has a long history of misleading us in many areas of scientific study.  So, when we find something new we can't yet explain, I'm not surprised to find that the idea that it might be caused by ETI is so appealing.  But, because of that very fact, I believe we need to be on guard against our natural inclinations.  So, requiring extraordinary evidence to support ET involvement is warranted.

#### Star One

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« Reply #99 on: 01/08/2018 07:31 PM »
Now this is an intriguing theory.

Quote
Based on our own experience, we expect that civilizations much older than ours will be scientifically savvy and hence technologically advanced. But it is also possible that a simpler lifestyle rather than scientific prosperity has dominated the political landscape on other planets, leading to old civilizations that are nevertheless technologically primitive.

#### M.E.T.

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« Reply #100 on: 01/08/2018 08:35 PM »
Now this is an intriguing theory.

Quote
Based on our own experience, we expect that civilizations much older than ours will be scientifically savvy and hence technologically advanced. But it is also possible that a simpler lifestyle rather than scientific prosperity has dominated the political landscape on other planets, leading to old civilizations that are nevertheless technologically primitive.

From my reading, this suffers from the same flaw that hampers so many attempted answers to the Fermi paradox. Namely that while this theory might apply to some alien civilizations, you only need one civilization that is aggressively expansionist to populate the entire galaxy with Von Neuman probes or some such scenario.

#### Star One

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« Reply #101 on: 01/08/2018 08:47 PM »
Now this is an intriguing theory.

Quote
Based on our own experience, we expect that civilizations much older than ours will be scientifically savvy and hence technologically advanced. But it is also possible that a simpler lifestyle rather than scientific prosperity has dominated the political landscape on other planets, leading to old civilizations that are nevertheless technologically primitive.

From my reading, this suffers from the same flaw that hampers so many attempted answers to the Fermi paradox. Namely that while this theory might apply to some alien civilizations, you only need one civilization that is aggressively expansionist to populate the entire galaxy with Von Neuman probes or some such scenario.

The latter seems unlikely even for an advanced civilisation due to the vast distances involved.

#### Lar

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« Reply #102 on: 01/08/2018 11:32 PM »
The distance from one end of a typical galaxy to another is not very far, even at very slow velocities, when measured in geological time scales.... 10 million years is not that long.
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#### Donosauro

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« Reply #103 on: 01/08/2018 11:46 PM »
...[Y]ou only need one civilization that is aggressively expansionist to populate the entire galaxy with Von Neuman probes or some such scenario.

How old is the oldest aggressively expansionist terrestrial civilization? And what is the TRL of our closest approximation to a Von Neuman probe?

#### RonM

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« Reply #104 on: 01/09/2018 12:02 AM »
The problem I have with the Fermi Paradox is its conclusion is based on assuming infinities. Back in 1950 when the Fermi Paradox got its start, the Steady State theory of the universe was a popular model and the Fermi Paradox assumption was reasonable given the infinite nature of the Steady State universe.

Now with the Big Bang theory as the accepted model, we know the universe has existed for a finite time. So, only a finite number of technological civilizations can have existed in our galaxy over that time.

Given a limited size and limited time, stating that there must at least one civilization that has already spread across the galaxy is an incorrect assumption.

#### QuantumG

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« Reply #105 on: 01/09/2018 12:14 AM »
The universe is about 14 billion years old... the Earth is about 4 billion years old and life started as quickly as it could, and here we are. So you're saying that for 10 billion years there was no other planets forming (wrong), or no life forming on those planets (why?)  Just a single Earth-like planet forming 4.1 billion years ago and developing along the same timeline as Earth would give a technological civilization 100 million years to spread across the universe. If it's possible, we should be able to see them. We can't see them - it's a paradox.

* All numbers rounded up to the nearest billion so I don't have to be annoyingly accurate, okay.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

#### RonM

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« Reply #106 on: 01/09/2018 01:37 AM »
The universe is about 14 billion years old... the Earth is about 4 billion years old and life started as quickly as it could, and here we are. So you're saying that for 10 billion years there was no other planets forming (wrong), or no life forming on those planets (why?)  Just a single Earth-like planet forming 4.1 billion years ago and developing along the same timeline as Earth would give a technological civilization 100 million years to spread across the universe. If it's possible, we should be able to see them. We can't see them - it's a paradox.

* All numbers rounded up to the nearest billion so I don't have to be annoyingly accurate, okay.

Wrong. I'm not talking about planet formation or how common life is in the galaxy. I'm talking about civilizations capable of interstellar travel. If you know anything about evolution, you know there is no predestined goal to intelligent species.

Plug in your favorite numbers into the Drake equation and come up with how many technological civilizations you think have existed in the galaxy. If it is high, say in the millions or billions, then there is a good chance the Fermi paradox is reasonable. However, if you put in pessimistic numbers and get only a handful of technological civilizations, then it isn't reasonable to assume one of the few has spread across the galaxy. Of course, you're just guessing based on your own preconceived ideas.

The Fermi paradox, like the Drake equation, is a great place to start examining possibilities, but it's not a scientific law.

#### QuantumG

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« Reply #107 on: 01/09/2018 01:48 AM »
If you know anything about evolution, you know there is no predestined goal to intelligent species.

How do you figure? So far we have one data sample and it made an intelligent species (kinda), so why wouldn't that happen more than once?

Quote from: RonM
The Fermi paradox, like the Drake equation, is a great place to start examining possibilities, but it's not a scientific law.

That's why it's called a paradox. No matter how you slice it the numbers indicate we're probably not the first or the only life in the universe and it shouldn't be too hard to make it known to other life that you're out there... and yet we see nothing. We're missing a part of the puzzle.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

#### RonM

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« Reply #108 on: 01/09/2018 02:15 AM »
If you know anything about evolution, you know there is no predestined goal to intelligent species.

How do you figure? So far we have one data sample and it made an intelligent species (kinda), so why wouldn't that happen more than once?

Quote from: RonM
The Fermi paradox, like the Drake equation, is a great place to start examining possibilities, but it's not a scientific law.

That's why it's called a paradox. No matter how you slice it the numbers indicate we're probably not the first or the only life in the universe and it shouldn't be too hard to make it known to other life that you're out there... and yet we see nothing. We're missing a part of the puzzle.

Of course intelligent can evolve on other worlds. That doesn't mean it will evolve on every world that has life. Natural selection favors the individuals with the best traits at the time. It's not necessarily a march to intelligent beings. So, the big question is how common is intelligent life? As you pointed out, we only have one data point.

OK, I'm fine with saying the Fermi paradox shows we're missing a part of the puzzle. It's just some people use it to dismiss alternate ideas, like the one in previous posts about most intelligent species not developing technology (a possible great filter).

Maybe there is evidence of an ancient interstellar probe in our solar system that we haven't found yet. There's lots of places we haven't looked yet, might not recognize an advanced vehicle, etc.

#### hop

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« Reply #109 on: 01/09/2018 02:16 AM »
Back in 1950 when the Fermi Paradox got its start, the Steady State theory of the universe was a popular model and the Fermi Paradox assumption was reasonable given the infinite nature of the Steady State universe.
This is not relevant to the original formulation of the Fermi Paradox. The crux of the "paradox" is the observation that one civilization with slow (i.e. far below the speed of light) travel can cover the galaxy on tens of million year timescales.

#### mme

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« Reply #110 on: 01/09/2018 02:18 AM »
If you know anything about evolution, you know there is no predestined goal to intelligent species.

How do you figure? So far we have one data sample and it made an intelligent species (kinda), so why wouldn't that happen more than once?

Quote from: RonM
The Fermi paradox, like the Drake equation, is a great place to start examining possibilities, but it's not a scientific law.

That's why it's called a paradox. No matter how you slice it the numbers indicate we're probably not the first or the only life in the universe and it shouldn't be too hard to make it known to other life that you're out there... and yet we see nothing. We're missing a part of the puzzle.
Earth has had 5 major extinction events and the human race almost went extinct 70,000 years ago.  I'd bet money there's lots of life in the universe and that intelligence has no doubt evolved other places and times. But I don't how often it gets to hang around to overlap close enough in space and time to detect one another.

Von Neumann probes are a fun idea but we have no idea if we or any species could get to that level of technology. I agree we are missing a part of the puzzle but my guess is that the existence of a functional technological society on a rock hurtling through space is a rare and ephemeral thing.

If there is other intelligent life in our galaxy. it's probably the Pierson's Puppeteers. That is the best explanation I have for our continued existence.
Space is not Highlander.  There can, and will, be more than one.

#### Johnnyhinbos

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« Reply #111 on: 01/09/2018 02:29 AM »
The universe is about 14 billion years old... the Earth is about 4 billion years old and life started as quickly as it could, and here we are. So you're saying that for 10 billion years there was no other planets forming (wrong), or no life forming on those planets (why?)  Just a single Earth-like planet forming 4.1 billion years ago and developing along the same timeline as Earth would give a technological civilization 100 million years to spread across the universe. If it's possible, we should be able to see them. We can't see them - it's a paradox.

* All numbers rounded up to the nearest billion so I don't have to be annoyingly accurate, okay.
This is exactly my thinking as well.

And to add to that, there’s enough time in the history of the universe that civilizations could have risen and fallen over and over again - and so even if they have since fallen, they most likely would have generated some “wavefront” of electromagnetic radiation at some point of their existence that we’d be able to detect - from some point of their own history. I mean, our own civilization is continually reducing radiated signals that escape our planet, we are more and more efficient with narrow beamed transmissions at higher and higher frequencies - but it’s too late, we’ve already sent out our calling card. Hitler at the 1936 Olympics is already out there. A timestamp of our own history. And I’m sure every developing civilization would have a period in their own history where their own wavefront pushed away from their planet.

Sure, if you’re not looking in the right place, at the right time, with the right sensitivity, you’d miss a signal - but we’re talking 14 billion years. That’s a LOT of time. A lot of time to leave these electromagnetic “footprints” throughout our galaxy.
John Hanzl. Author, action / adventure www.johnhanzl.com

#### JH

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« Reply #112 on: 01/09/2018 03:06 AM »
The universe is about 14 billion years old... the Earth is about 4 billion years old and life started as quickly as it could, and here we are. So you're saying that for 10 billion years there was no other planets forming (wrong), or no life forming on those planets (why?)  Just a single Earth-like planet forming 4.1 billion years ago and developing along the same timeline as Earth would give a technological civilization 100 million years to spread across the universe. If it's possible, we should be able to see them. We can't see them - it's a paradox.

The problem with this is your assumption of uniform source material for solar system formation throughout the history of the universe. This isn't the case, as heavy element enrichment has progressed steadily over generations of stellar development. As a result, while it seems entirely reasonable—and might in fact be so—that another technological civilization could have developed 100 Ma, we cannot be certain that this is true. We might be at the very beginning of the "viable stage" of the universe's development, either because life has certain prerequisites or because technological civilization cannot develop without ready access to large quantities of elements such as iron, for example.

Don't take this as me dismissing the Fermi paradox entirely, but appreciate that we don't fully understand what physical conditions were needed for us to be here.

#### notsorandom

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« Reply #113 on: 01/09/2018 03:59 AM »
Well someone has to be the first one to the party. One explanation to the Fermi Paradox is that we are the first to evolve intelligence, in our neighborhood at least. It could be that intelligent life will be very common but hasn't had time to become common yet. The first few intelligent species may find themselves noticing that the universe should be full of others but don't see them yet.

#### deruch

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« Reply #114 on: 01/09/2018 11:35 AM »
What's the path to advanced technologies without fossil fuels?  Much of human technological advancement beyond wind-powered and hydro-mechanical has relied on an idiosyncratic quirk of our planetary history.  Steps to solar or nuclear power, or industrial scale wind-/hydro- power without a robust energy system seem challenging.

#### Star One

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« Reply #115 on: 01/09/2018 04:52 PM »
It’s Never Aliens—until It Is

Quote
What do a strangely fading faraway star, an oddly shaped interstellar interloper in the solar system and a curious spate of UFO sightings by members of the U.S. military all have in common?
They are all mysterious, for one thing—eye-catchingly weird, yet still just hazy outlines that let the imagination run wild. All have recently generated headlines as possible signs of life and intelligence beyond Earth, of some mind-bogglingly advanced alien culture revealing its existence at last to our relatively primitive and planetbound civilization. Yet their most salient shared trait so far is the certainty they provoke in most scientists, who insist these developments represent nothing so sensational. Ask a savvy astronomer or physicist about any of these oddities, and they will tell you, as they have time and time before: It’s not aliens. In fact, it’s never aliens.
Far from being close-minded killjoys, most scientists in the “never aliens” camp desperately want to be convinced otherwise. Their default skeptical stance is a prophylactic against the wiles of wishful thinking, a dare to true believers to provide extraordinary evidence in support of extraordinary claims. What is really extraordinary, the skeptics say, is not so much the possibility of extraterrestrial intelligence but rather the notion that its existence nearby or visitation of Earth could be something easily unnoticed or overlooked. If aliens are out there—or even right here—in abundance, particularly ones wildly advanced beyond our state, why would incontrovertible proof of that reality be so annoyingly elusive?

https://www.scientificamerican.com/article/its-never-aliens-until-it-is/

#### hop

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« Reply #116 on: 01/09/2018 05:11 PM »
The problem with this is your assumption of uniform source material for solar system formation throughout the history of the universe. This isn't the case, as heavy element enrichment has progressed steadily over generations of stellar development. As a result, while it seems entirely reasonable—and might in fact be so—that another technological civilization could have developed 100 Ma, we cannot be certain that this is true. We might be at the very beginning of the "viable stage" of the universe's development, either because life has certain prerequisites or because technological civilization cannot develop without ready access to large quantities of elements such as iron, for example.
IMHO, this doesn't really work. Metallicity varies locally depending on the history and of the star forming region, and most heavy elements are produced by short lived stars. I don't know what the current estimates are for the earliest Solar metallicity stars is, but it's surely billions of years earlier than our solar system. Wikipedia suggests solar metallicity stars with ages over 10 billion years are known.

#### whitelancer64

« Reply #117 on: 01/09/2018 05:53 PM »
If you know anything about evolution, you know there is no predestined goal to intelligent species.

How do you figure? So far we have one data sample and it made an intelligent species (kinda), so why wouldn't that happen more than once?

Quote from: RonM
The Fermi paradox, like the Drake equation, is a great place to start examining possibilities, but it's not a scientific law.

That's why it's called a paradox. No matter how you slice it the numbers indicate we're probably not the first or the only life in the universe and it shouldn't be too hard to make it known to other life that you're out there... and yet we see nothing. We're missing a part of the puzzle.

Life is probably extremely prevalent across the universe. I would expect virtually every habitable planet to be host to life forms.

However.

Simple, single-celled life forms were the only life on Earth for 3.5 billion years. We don't know why life jumped from simple, single-celled forms to multiple-celled critters. The Cambrian explosion was sudden and there's not much evidence available that can clue us in to why it happened, though it's an area of intense research. It's entirely possible that a planet could be inhabited by bacteria for tens of billions of years without any more complex life forming, particularly because we don't yet understand how it happened here.

Even if complex life forms, there's no guarantee that intelligence will arise. A whole host of complex environmental factors as well as a lot of evolutionary luck led to us. It's plain luck, for example, that we have both intelligence and dextrous hands able to create and manipulate complex tools.

Consider that Dolphins are very smart, but ... flippers. There could be very intelligent life forms swimming in alien seas, but smelting metals would be an entirely alien concept to them. They would never form a technological civilization.

There's also the material resources. Let's say a star system with a habitable planet formed 1 billion years after the big bang - it could be metal poor, if not enough stars had gone supernova by that point to produce vast quantities of iron, and so on. Intelligent life forms there wouldn't have much of the materials needed to form a technological civilization like we have.

We also have an abundance of calorie-rich food sources, many with seeds that are storable as grains. Farming these food sources allowed us to have much more "leisure time" to create and build technology and civilizations, rather than just hunting and gathering all the time. There's no guarantee that such food sources would be available on an alien world.

There's many more such examples if you think about it for a while.
« Last Edit: 01/09/2018 06:01 PM by whitelancer64 »
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

#### jebbo

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« Reply #118 on: 01/09/2018 06:12 PM »
IMHO, this doesn't really work. Metallicity varies locally depending on the history and of the star forming region, and most heavy elements are produced by short lived stars. I don't know what the current estimates are for the earliest Solar metallicity stars is, but it's surely billions of years earlier than our solar system. Wikipedia suggests solar metallicity stars with ages over 10 billion years are known.

I'd agree you can certainly get Solar metallicity stars much earlier ... I'm not that familiar with the literature in this area, but there's *loads* of studies of the age/metallicity relationship e.g. https://arxiv.org/abs/1704.07189

Edit: and this one gives a nice taster of what we can expect from Gaia for the Milky way https://arxiv.org/abs/1801.01427

--- Tony
« Last Edit: 01/09/2018 06:22 PM by jebbo »

#### Dao Angkan

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« Reply #119 on: 01/09/2018 08:22 PM »
Yep, we can say that average metallicity increases with time, but the sun isn't even average for it's age. If 10Gya stars can have the same metallicity as Sol (which is older than the projected lifetime of the sun), then metallicity really shouldn't be an explanation for the Fermi paradox.

#### Dao Angkan

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« Reply #120 on: 01/09/2018 08:39 PM »
Simple, single-celled life forms were the only life on Earth for 3.5 billion years. We don't know why life jumped from simple, single-celled forms to multiple-celled critters. The Cambrian explosion was sudden and there's not much evidence available that can clue us in to why it happened, though it's an area of intense research. It's entirely possible that a planet could be inhabited by bacteria for tens of billions of years without any more complex life forming, particularly because we don't yet understand how it happened here.

This is really debatable, some argue that cyanobacteria were multicellular 3.5Gya, others differentiate between those and "complex multicellular organisms" (roughly the timescale that you argue for). I think that one thing that most agree on is that "complex life" could not have evolved without prior "basic life" oxygenating the atmosphere over several billions of years.
« Last Edit: 01/09/2018 08:40 PM by Dao Angkan »

#### QuantumG

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« Reply #121 on: 01/09/2018 09:08 PM »
The argument that we can't generalize about life in the universe as we only have one data sample (life on Earth) is a good one.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

#### whitelancer64

« Reply #122 on: 01/09/2018 09:18 PM »
It's a lot like many physics problems. Assume a perfectly spherical mass of 1 kg on a perfectly flat, frictionless plane... now apply to real life situation.
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
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#### Dao Angkan

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« Reply #123 on: 01/09/2018 09:22 PM »
We don't need to generalise, we can restrict the question to "life as we know it". We know that "life as we know it" is possible, what we don't know is how likely it is (although how soon it happened on Earth suggests that it is quite likely, but maybe it takes so long for intelligence to evolve that only the planets that are lucky enough to evolve life quickly have enough time to evolve intelligence before the star dies).

It's quite possible that within many of our lifetimes that we will have a census of habitable zone terrestrial planet atmospheres. If we can detect O2 percentages in some atmospheres, then we can at least know that we're not unique (although we won't be able to prove that it was due to biological processes). Alternatively, we could find that no other planets have detectable levels of biomarkers, which would be an equally profound discovery.
« Last Edit: 01/09/2018 09:36 PM by Dao Angkan »

#### Dao Angkan

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« Reply #124 on: 01/09/2018 10:52 PM »
Now this is an intriguing theory.

Quote
Based on our own experience, we expect that civilizations much older than ours will be scientifically savvy and hence technologically advanced. But it is also possible that a simpler lifestyle rather than scientific prosperity has dominated the political landscape on other planets, leading to old civilizations that are nevertheless technologically primitive.

From my reading, this suffers from the same flaw that hampers so many attempted answers to the Fermi paradox. Namely that while this theory might apply to some alien civilizations, you only need one civilization that is aggressively expansionist to populate the entire galaxy with Von Neuman probes or some such scenario.

The latter seems unlikely even for an advanced civilisation due to the vast distances involved.

Astronomically speaking it would take very little time for a space faring civilisation to colonise the whole galaxy. If a civilisation "just" colonises the nearest 100 stars, and only 1% of those does the same, then exponentially the entire Milky Way would be colonised in as little as hundreds of thousands of years, maybe more realistically in tens of millions of years. If we assume that Earth like planets first started to be formed 10Gya, then the galaxy should have been colonised many times over.

We could argue that interstellar travel isn't practicle, but most stars aren't that far from each other, at 10% lightspeed most systems' closest stars should be achievable in current human lifetimes.

It should be noted that the earliest homo sapiens are thought to be 300,000 years old, theoretically we could colonise the entire galaxy in less time than we took to invent the microprocessor.
« Last Edit: 01/09/2018 11:02 PM by Dao Angkan »

#### Star One

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« Reply #125 on: 01/10/2018 07:23 PM »
SETI project homes in on strange ‘fast radio bursts’

Quote
Another possibility, though remote, is that the FRB is a high-powered signal from an advanced civilization. Hence the interest of Breakthrough Listen, which looks for signs of intelligent life in the universe, funded by $100 million over 10 years from internet investor Yuri Milner. “Although it’s extremely unlikely that pulses we have detected from FRB 121102 were transmitted by ETs, we would like to test various ET hypotheses for the FRB type transient signals in general,” Gajjar said. Breakthrough Listen has to date recorded data from a dozen FRBs, including FRB 121102, and plans eventually to sample all 30-some known sources of fast radio bursts. “We want a complete sample so that we can conduct our standard SETI analysis in search of modulation patterns or narrow-band signals – any kind of information-bearing signal emitted from their direction that we don’t expect from nature,” he said. http://news.berkeley.edu/2018/01/10/seti-project-homes-in-on-strange-fast-radio-bursts/ #### missinglink • Full Member • Posts: 123 • Liked: 18 • Likes Given: 107 ##### Re: General SETI Thread « Reply #126 on: 01/11/2018 10:22 PM » but it’s too late, we’ve already sent out our calling card. Hitler at the 1936 Olympics is already out there. A timestamp of our own history. That seems unlikely to me. Signal strength is so low to begin with and diminishes rapidly due to the inverse-square law, the signal becomes lost in noise not long after leaving the solar system. Of course, the reverse is true as well. From Wikipedia's article on SETI: Quote For SERENDIP and most other SETI projects to detect a signal from an extraterrestrial civilization, the civilization would have to be beaming a powerful signal directly at us. The image this calls to mind is that of a soap bubble. You can touch it while it is expanding and moving, but only for a short time, then it pops (similar to EM radiation becoming too weak to detect). Admittedly, the Intro to CONTACT (the movie starring Jodie Foster) showing successive broadcast signals going out into deep space was very cool #### M.E.T. • Full Member • Posts: 553 • Liked: 225 • Likes Given: 18 ##### Re: General SETI Thread « Reply #127 on: 01/12/2018 05:44 AM » but it’s too late, we’ve already sent out our calling card. Hitler at the 1936 Olympics is already out there. A timestamp of our own history. That seems unlikely to me. Signal strength is so low to begin with and diminishes rapidly due to the inverse-square law, the signal becomes lost in noise not long after leaving the solar system. Of course, the reverse is true as well. From Wikipedia's article on SETI: Quote For SERENDIP and most other SETI projects to detect a signal from an extraterrestrial civilization, the civilization would have to be beaming a powerful signal directly at us. The image this calls to mind is that of a soap bubble. You can touch it while it is expanding and moving, but only for a short time, then it pops (similar to EM radiation becoming too weak to detect). Admittedly, the Intro to CONTACT (the movie starring Jodie Foster) showing successive broadcast signals going out into deep space was very cool That's why I don't see the lack of radio signals as an issue as far as the Fermi Paradox is concerned. It is quite plausible that most general signals originate from too far away too reach us, and that no one feels it is worth the effort to send a high powered beam directly to us, in the hope of hearing back in a few thousand years. The lack of physical evidence of ET intelligence, such as Von Neuman probes, distant megastructures etc. is what seems like a stronger argument to me. We might receive a signal from another star one day, but I don't see the lack of such a signal as a problem. #### Johnnyhinbos • Full Member • Posts: 1343 • Boston, MA • Liked: 1493 • Likes Given: 212 ##### Re: General SETI Thread « Reply #128 on: 01/12/2018 11:14 AM » John Hanzl. Author, action / adventure www.johnhanzl.com #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### General SETI Thread « Reply #129 on: 01/16/2018 07:19 PM » Persuasive article by Jason Wright arguing that SETI should be part of NASA’s astrobiology strategy. With in my view some well deserved criticism of NASA in the astrobiology arena. Quote What follows is my submission to the National Academies of Sciences, Engineering, and Medicine ad hoc Committee on Astrobiology Science Strategy for Life in the Universe, 2018. It is available as a PDF here. Please also see Jill Tarter’s companion white paper here. http://sites.psu.edu/astrowright/2018/01/16/seti-is-part-of-astrobiology/ « Last Edit: 01/16/2018 07:28 PM by Star One » #### moreno7798 ##### Re: General SETI Thread « Reply #130 on: 01/16/2018 10:57 PM » My bet is that to the universe earth is basically a niche extremophile environment. Think about it, a planet living very close to a hot star. So hot that biology becomes liquid. Water may be one of the most dangerous poisonous liquids in the universe but hey we're made of it so that's what we think life is composed of. The vast majority of the universe may sees us as the extremophiles of the universe. That is because the vast majority of the universe probably lives in in much colder and darker environments where energy is not derived from heat and Photosynthesis is not a thing. Any aliens living in those environments are probably not sending signals to planets close to stars. They could be looking in the space between the stars. The perception of where life in the universe may lie is relative to your perception of what life may be. They probably consider anything that close to a star to be devoid of life. That could be a possible solution to the Fermi Paradox. #### RotoSequence • Full Member • Posts: 906 • Liked: 648 • Likes Given: 829 ##### Re: General SETI Thread « Reply #131 on: 01/17/2018 12:12 AM » My bet is that to the universe earth is basically a niche extremophile environment. Think about it, a planet living very close to a hot star. So hot that biology becomes liquid. Water may be one of the most dangerous poisonous liquids in the universe but hey we're made of it so that's what we think life is composed of. The vast majority of the universe may sees us as the extremophiles of the universe. That is because the vast majority of the universe probably lives in in much colder and darker environments where energy is not derived from heat and Photosynthesis is not a thing. Any aliens living in those environments are probably not sending signals to planets close to stars. They could be looking in the space between the stars. The perception of where life in the universe may lie is relative to your perception of what life may be. They probably consider anything that close to a star to be devoid of life. That could be a possible solution to the Fermi Paradox. It's a fun idea for sci-fi authors, but interesting chemistry with common elements seems to prefer Room Temperature. #### Welsh Dragon • Full Member • Posts: 261 • Liked: 255 • Likes Given: 34 ##### Re: General SETI Thread « Reply #132 on: 01/17/2018 07:55 AM » <snip>. Water may be one of the most dangerous poisonous liquids in the universe but hey we're made of it so that's what we think life is composed of. </snip> Oxygen is the poison, not water. #### Bynaus • Full Member • Posts: 458 • Planetary Scientist • Switzerland • Liked: 308 • Likes Given: 210 ##### Re: General SETI Thread « Reply #133 on: 01/17/2018 08:32 AM » Quote The perception of where life in the universe may lie is relative to your perception of what life may be. Maybe - but the argument of mediocrity (we are much more likely to be typical, rather than atypical) would suggest that this is a low-probability suggestion. #### RotoSequence • Full Member • Posts: 906 • Liked: 648 • Likes Given: 829 ##### Re: General SETI Thread « Reply #134 on: 01/17/2018 08:46 AM » Quote The perception of where life in the universe may lie is relative to your perception of what life may be. Maybe - but the argument of mediocrity (we are much more likely to be typical, rather than atypical) would suggest that this is a low-probability suggestion. The Kepler dataset shows that The Solar System has an uncommon arrangement of planets compared to most stars. The odds may be long, but sometimes you hit the jackpot, and space gives you trillions of chances to try your odds. #### jebbo • Full Member • Posts: 585 • Cambridge, UK • Liked: 235 • Likes Given: 224 ##### Re: General SETI Thread « Reply #135 on: 01/17/2018 09:18 AM » The Kepler dataset shows that The Solar System has an uncommon arrangement of planets compared to most stars. The odds may be long, but sometimes you hit the jackpot, and space gives you trillions of chances to try your odds. We're not really that sure of the occurrence rates of systems like ours yet as it is very hard to detect systems with a similar architecture to ours (and not just for Kepler). Yes, they seem to be rarer, but how rare is unknown. Essentially all current detection methods are biased towards larger planets on shorter period orbits. So the catalogues are strongly biased towards compact systems & hot Jupiters ... However, RV searches have yielded a number of Jupiter analogues - but this requires >10 years of data, so the number of systems is limited. We'll have a better idea (at least for Jupiter-analogue occurrence rates) in a few years when the Gaia planet catalogue is released as astrometry is biased towards finding planets on wider orbits (from memory, Jupiter distance is about the optimum). --- Tony #### Bynaus • Full Member • Posts: 458 • Planetary Scientist • Switzerland • Liked: 308 • Likes Given: 210 ##### Re: General SETI Thread « Reply #136 on: 01/17/2018 10:00 AM » Quote The perception of where life in the universe may lie is relative to your perception of what life may be. Maybe - but the argument of mediocrity (we are much more likely to be typical, rather than atypical) would suggest that this is a low-probability suggestion. The Kepler dataset shows that The Solar System has an uncommon arrangement of planets compared to most stars. The odds may be long, but sometimes you hit the jackpot, and space gives you trillions of chances to try your odds. But most of the times, you don't hit the jackpot. So the proposal of having hit it (without knowing) must be characterized as a low-probability proposition. This is all I am saying. For the Kepler system, as jebbo just mentioned, its not yet fully clear what this means. But on top of that, there might be an anthropic bias involved (of which we are not yet aware), so that compact systems might be less habitable. There is a similar situation with the Sun not being an M-dwarf although the latter being very common: you could explain this by "luck", but perhaps M-dwarfs are just not as habitable as G-dwarfs. #### M.E.T. • Full Member • Posts: 553 • Liked: 225 • Likes Given: 18 ##### Re: General SETI Thread « Reply #137 on: 01/17/2018 10:04 AM » Can someone help me to understand some of the parameters of the Mediocrity Principle. Because to me it seems you need to massage these parameters rather creatively to get to some kind of Mediocrity assumption. For example, in our own solar system, we are the only one of eight planets that has intelligent life, most likely the only one out of eight that has any complex life, and as far as we know, the only one with even simple life. So clearly, we aren't mediocre within the population of our Solar System. We are quite unique. Next, our Sun, based on some cursory Googling, appears to be of a type (G-type main sequence), that only represents 5% or so of all observable stars in the Universe. So once again, we can't really say that sun-like stars are mediocre, if they only represent one in twenty stars out there. Obviously this list can go on, for example the relative size and influence of our Moon would appear not to be mediocre at all, etc. etc. My point being, under what parameters do we feel that our planet should be considered "Mediocre"? Or is it based more on a philosophical principle, rather than any kind of physical evidence? « Last Edit: 01/17/2018 10:07 AM by M.E.T. » #### Alpha_Centauri • Full Member • Posts: 608 • England • Liked: 208 • Likes Given: 122 ##### Re: General SETI Thread « Reply #138 on: 01/17/2018 10:27 AM » You weren't claiming that the Earth or the Solar System were rare, you were claiming that life such as ours is extreme compared to life elsewhere in the universe. Those are two different arguments. Simple probability dictates that it is unlikely by chance to happen to find yourself a member of an extreme group, just as it is unlikely to pick out the one red ball in a bag of 9 other black balls, so the default (though not necessarily correct) assumption is that we are unlikely to be that unusual in the context of other life. This of course is rather negated if we are the first example of sentient life so the bag is low on balls. This is a separate question to the rarity of the conditions in which we formed. Think of it like this, you have 5 oases in a 1000 sq km desert. The chances that the first oasis you come across hosts very different life to that in the other four is low, but this has no relation to the rarity of the conditions (an oasis in the desert) that allows any of these ecosystems to develop. « Last Edit: 01/17/2018 10:36 AM by Alpha_Centauri » #### M.E.T. • Full Member • Posts: 553 • Liked: 225 • Likes Given: 18 ##### Re: General SETI Thread « Reply #139 on: 01/17/2018 10:31 AM » You weren't claiming that the Earth or the Solar System were rare, you were claiming that life such as ours is extreme compared to life elsewhere in the universe. Those are two different arguments. Simple probability dictates that it is unlikely by chance to happen to find yourself a member of an extreme group, just as it is unlikely to pick out the one red ball in a bag of 9 other black balls, so the default (though not necessarily correct) assumption is that we are unlikely to be that unusual in the context of other life. This of course is rather negated if we are the first example of sentient life so the bag is low on balls. This is a separate question to the rarity of the conditions in which we formed. Think of it like this, you have 5 oases in a 1000 sq km desert. The chances that the first oasis you come across is hosts radically different life to that in the other four is low, but this has no relation to the rarity of the conditions (an oasis in the desert) that allows any of these ecosystems to develop. Sorry, I thought the whole point of the Mediocrity Principle is that neither the Earth nor the fact that it has life on it is particularly special. #### jebbo • Full Member • Posts: 585 • Cambridge, UK • Liked: 235 • Likes Given: 224 ##### Re: General SETI Thread « Reply #140 on: 01/17/2018 10:32 AM » For the Kepler system, as jebbo just mentioned, its not yet fully clear what this means. But on top of that, there might be an anthropic bias involved (of which we are not yet aware), so that compact systems might be less habitable. There is a similar situation with the Sun not being an M-dwarf although the latter being very common: you could explain this by "luck", but perhaps M-dwarfs are just not as habitable as G-dwarfs. Given their activity when young, I lean towards the view that planets around M-dwarfs are less likely to be habitable due to atmosphere / volatiles being stripped. Some might be habitable, but this depends on formation models and the initial volatile fraction ... --- Tony #### Bynaus • Full Member • Posts: 458 • Planetary Scientist • Switzerland • Liked: 308 • Likes Given: 210 ##### Re: General SETI Thread « Reply #141 on: 01/17/2018 10:55 AM » For the Kepler system, as jebbo just mentioned, its not yet fully clear what this means. But on top of that, there might be an anthropic bias involved (of which we are not yet aware), so that compact systems might be less habitable. There is a similar situation with the Sun not being an M-dwarf although the latter being very common: you could explain this by "luck", but perhaps M-dwarfs are just not as habitable as G-dwarfs. Given their activity when young, I lean towards the view that planets around M-dwarfs are less likely to be habitable due to atmosphere / volatiles being stripped. Some might be habitable, but this depends on formation models and the initial volatile fraction ... --- Tony I lean towards agreeing with you. Stripping of atmospheres, combined with tidal lock. While I know that some models suggest that tidal lock and backside freezout is not a big problem if the atmosphere is thick enough, it still erases quite a bit of the habitable parameter space (i.e., if the atmosphere is not thick enough). Combine this with atmospheric erosion and the lack of a strong magnetic field due to slow, locked rotation (further helping with that atmospheric erosion) and we end up in a situation where most rocky planets around M-dwarfs would be poor in volatiles. There might be caveats (e.g., the low density of some of the Trappist-1 planets, although within large errors), and perhaps habitability doesn't really need an atmosphere (-> Europa, Enceladus), but at least Earth-like planets will have a hard time to survive long enough to come up with complex life around an M-dwarf. #### jebbo • Full Member • Posts: 585 • Cambridge, UK • Liked: 235 • Likes Given: 224 ##### Re: General SETI Thread « Reply #142 on: 01/17/2018 11:08 AM » Yes, and I'm interested to see whether those low densities hold up when we get RV data (hopefully soonish from SPIRou). In particular, for "b", which I had pegged as an Io-analogue ... I love these compact systems with near-MMR resonance chains! Hopefully TESS will find a few more of them (there's a new TESS M-dwarf yield paper on arxiv today: https://arxiv.org/abs/1801.04949) Edit: this does relate to the discussion on "mediocrity" and is not just tangential: if the chances of M-dwarf planets being habitable are substantially less than those for FGK stars, the fact that we orbit a G star becomes less surprising, even though most planets may be around M-dwarfs. --- Tony « Last Edit: 01/17/2018 11:16 AM by jebbo » #### Alpha_Centauri • Full Member • Posts: 608 • England • Liked: 208 • Likes Given: 122 ##### Re: General SETI Thread « Reply #143 on: 01/17/2018 11:13 AM » You weren't claiming that the Earth or the Solar System were rare, you were claiming that life such as ours is extreme compared to life elsewhere in the universe. Those are two different arguments. Simple probability dictates that it is unlikely by chance to happen to find yourself a member of an extreme group, just as it is unlikely to pick out the one red ball in a bag of 9 other black balls, so the default (though not necessarily correct) assumption is that we are unlikely to be that unusual in the context of other life. This of course is rather negated if we are the first example of sentient life so the bag is low on balls. This is a separate question to the rarity of the conditions in which we formed. Think of it like this, you have 5 oases in a 1000 sq km desert. The chances that the first oasis you come across is hosts radically different life to that in the other four is low, but this has no relation to the rarity of the conditions (an oasis in the desert) that allows any of these ecosystems to develop. Sorry, I thought the whole point of the Mediocrity Principle is that neither the Earth nor the fact that it has life on it is particularly special. If every star system in our galaxy has 8 planets with only one of them being habitable, then is the Earth special for being a one-in-eight occurrence or nothing much to write home about because there would be ~100 Billion earths in our galaxy? You are getting hung-up on the term mediocrity, we are really talking about probabilities. Probabilities are set-dependant. "Special" is relative to the set you are considering. « Last Edit: 01/17/2018 11:38 AM by Alpha_Centauri » #### Alpha_Centauri • Full Member • Posts: 608 • England • Liked: 208 • Likes Given: 122 ##### Re: General SETI Thread « Reply #144 on: 01/17/2018 11:23 AM » As for the M-dwarf habitability thing, personally I would first like to see what the inferred volatile content of the first few M-dwarf planets to have their atmosphere probed (and properties well constrained) is like. We have a lot of educated guesses theory but very little actual observational evidence to back it up as yet. « Last Edit: 01/17/2018 11:27 AM by Alpha_Centauri » #### jebbo • Full Member • Posts: 585 • Cambridge, UK • Liked: 235 • Likes Given: 224 ##### Re: General SETI Thread « Reply #145 on: 01/17/2018 11:28 AM » Yup. Which is why I brought up TESS and that paper, which has the opening line: Quote NASA’s TESS Mission (Ricker et al. 2014) will furnish the vast majority of small, rocky planets for atmospheric study --- Tony #### M.E.T. • Full Member • Posts: 553 • Liked: 225 • Likes Given: 18 ##### Re: General SETI Thread « Reply #146 on: 01/17/2018 11:36 AM » You weren't claiming that the Earth or the Solar System were rare, you were claiming that life such as ours is extreme compared to life elsewhere in the universe. Those are two different arguments. Simple probability dictates that it is unlikely by chance to happen to find yourself a member of an extreme group, just as it is unlikely to pick out the one red ball in a bag of 9 other black balls, so the default (though not necessarily correct) assumption is that we are unlikely to be that unusual in the context of other life. This of course is rather negated if we are the first example of sentient life so the bag is low on balls. This is a separate question to the rarity of the conditions in which we formed. Think of it like this, you have 5 oases in a 1000 sq km desert. The chances that the first oasis you come across is hosts radically different life to that in the other four is low, but this has no relation to the rarity of the conditions (an oasis in the desert) that allows any of these ecosystems to develop. Sorry, I thought the whole point of the Mediocrity Principle is that neither the Earth nor the fact that it has life on it is particularly special. If every star system in our galaxy has 8 planets with only one of them being habitable, then is the Earth special for being a one-in-eight occurrence or nothing much to write home about because there would be ~100 Billion earths in our galaxy? You are getting hung-up on the term mediocrity, we are really talking about probabilities. Probabilities are set-dependant. "Special" is relative to the set you are considering. I think that is what I'm trying to get at. Which is that the definition of the "set" is based on a lot of assumptions, and if you add enough conditions that must be met by the set, the population of the set might well drop very low. For example. You used an example population of 100 billion stars in the galaxy. Then yes, if that is the extent of the criteria that allows for inclusion in the set, there should indeed be many planets like ours. However, if we narrow it down to sun-like stars, that drops the size of the population to say 20 billion (random number for sake of argument). If only 10% of those have rocky planets in the habitable zone, that drops it down to 2 billion. If only 10% of those are in the right region of the galaxy, that drops it down to 200 million. If only 10% of those have plate tectonics, then you are down to 20 million. Add the need for a Moon similar to ours, and it may cut that number by a factor of 1000, bringing us down to 20,000. These are just random criteria with random probabilities added for sake of demonstration. But the point is, if you define the "set" with sufficient criteria (many of whom we may not be aware of yet), it is quite conceivable that we may indeed end up being a typical member of a set containing a grand total of 1 star system or fewer. I think that is basically the Rare Earth Hypothesis just rephrased in fairly clumsy manner by me. « Last Edit: 01/17/2018 11:42 AM by M.E.T. » #### Alpha_Centauri • Full Member • Posts: 608 • England • Liked: 208 • Likes Given: 122 ##### Re: General SETI Thread « Reply #147 on: 01/17/2018 11:50 AM » Yes that is all well and true but, getting back to the original point, we are unlikely to be an extreme member of the set of sentient life. How rare that set is is dependant on a lot of variables. If it is so rare you could count the members on your hand it makes little sense to be talking about extremes in the first place. « Last Edit: 01/17/2018 11:54 AM by Alpha_Centauri » #### M.E.T. • Full Member • Posts: 553 • Liked: 225 • Likes Given: 18 ##### Re: General SETI Thread « Reply #148 on: 01/17/2018 12:03 PM » Yes that is all well and true but, getting back to the original point, we are unlikely to be an extreme member of the set of sentient life. How rare that set is is dependant on a lot of variables. If it is so rare you could count the members on your hand it makes little sense to be talking about extremes in the first place. OK, maybe I'm arguing about the wrong thing here, then. In my experience the Mediocrity Principle is usually invoked to argue against the idea that life (let's focus on sentient life in this case) is rare in the Universe. I have never seen it used to argue that other sentient life should be fairly similar to us. But I guess it can be applied in that manner too. But sure, that's not the argument I was engaging in. My focus was on whether there is other sentient life at all. « Last Edit: 01/17/2018 12:05 PM by M.E.T. » #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### General SETI Thread « Reply #149 on: 01/17/2018 04:34 PM » For the Kepler system, as jebbo just mentioned, its not yet fully clear what this means. But on top of that, there might be an anthropic bias involved (of which we are not yet aware), so that compact systems might be less habitable. There is a similar situation with the Sun not being an M-dwarf although the latter being very common: you could explain this by "luck", but perhaps M-dwarfs are just not as habitable as G-dwarfs. Given their activity when young, I lean towards the view that planets around M-dwarfs are less likely to be habitable due to atmosphere / volatiles being stripped. Some might be habitable, but this depends on formation models and the initial volatile fraction ... --- Tony Well being as nature constantly surprises us, plus these models are still being refined almost it seems on a yearly basis I wouldn’t bet your house on the inhospitably of M dwarf class systems. Especially as we know nothing of the atmospheres of the planets in such systems. « Last Edit: 01/17/2018 04:35 PM by Star One » #### CuddlyRocket ##### Re: General SETI Thread « Reply #150 on: 01/17/2018 07:14 PM » Next, our Sun, based on some cursory Googling, appears to be of a type (G-type main sequence), that only represents 5% or so of all observable stars in the Universe. 'In the Universe' over-estimates the strength of our knowledge of star population distributions. Basically, we can only do surveys within range of our telescopes - which is longer for brighter stars - which we can call our 'solar neighbourhood'. And then we have to add the caveat that our neighbourhood may not be typical - but we can pray in aid the principle of mediocrity there! So, in the solar neighbourhood, 7.5% of stars are Class G main sequence. Class K are 12% and Class M, 76%. (For completeness, Class F 3%, Class A 0.63%, Class B 0.13% and Class O 0.00003%.) Though Gaia will be doing a more complete survey, so it will be interesting to see if these figures shift significantly. #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #151 on: 01/20/2018 08:12 PM » New article from Jason Wright pointing out how SETI is marginalised by other astronomers http://sites.psu.edu/astrowright/2018/01/20/seti-is-not-about-getting-attention/ #### ikke666 • Member • Posts: 29 • Liked: 0 • Likes Given: 2 ##### Re: General SETI Thread « Reply #152 on: 01/21/2018 04:47 PM » a little question is it possible to put seti @home on a raspberri pi? if yes, where can i find the documentation to do so step by step? #### Paul451 • Full Member • Posts: 1383 • Australia • Liked: 679 • Likes Given: 575 ##### Re: General SETI Thread « Reply #153 on: 01/29/2018 09:45 PM » if you add enough conditions that must be met by the set, the population of the set might well drop very low. For example. You used an example population of 100 billion stars in the galaxy. [..] if we narrow it down to sun-like stars, that drops the size of the population to say 20 billion [..] If only 10% of those have rocky planets in the habitable zone, that drops it down to 2 billion. If only 10% of those are in the right region of the galaxy, that drops it down to 200 million. If only 10% of those have plate tectonics, then you are down to 20 million. [etc] Congratulations, you've just reinvented the Drake Equation. Can someone help me to understand some of the parameters of the Mediocrity Principle. It's just the idea that across measurable traits, 95% of the time we should be within the middle 95% of measured values. 50% of traits we should be in the middle 50%, 25% of traits we should be in the top 25%, another 25% we should be in the bottom 25%. And so on and so on. It's... well, a pretty mundane principle. The thing you seem to miss is that the same Principle says that we shouldn't expect to be "average". By chance alone, you've the same probability of being in the top 10% as in the middle 10%. Measure enough traits and we're going to fall in the high or low end, or dead centre, of some of them simply by chance. The Mediocrity Principle just serves as a warning not to read too much into that. For example, in our own solar system, we are the only one of eight planets that has intelligent life, most likely the only one out of eight that has any complex life, and as far as we know, the only one with even simple life. 1 in 8. 12.5%. Mundane result. (I'd also say that 100% of planets within the Sun's habitable zone have life, but that's circular reasoning, obviously. Anthropic principle.) Next, our Sun, based on some cursory Googling, appears to be of a type (G-type main sequence), that only represents 5% or so of all observable stars in the Universe. Within the middle 95%. Not "average", but still mundane. (5% also leaves you with 10 billion stars to play with in just this galaxy.) But that's an arbitrary, human made category. Why only G and not G+K? Or F+G+K? Or why all of G, and not just G2V? This is where having a sample size of 1 hurts us. We know that the range of conditions supporting life, intelligence and technological civilisation includes Earth, but how narrowly is it prescribed around Earth? We don't know. My point being, under what parameters do we feel that our planet should be considered "Mediocre"? Or is it based more on a philosophical principle, rather than any kind of physical evidence? In a Bayesian probability calculation, it serves as your prior probability. That's all. For example: Kepler (and other systems for detecting planets) have a bias towards finding larger and closer planets. So when you look at the data, how do you tell what's significant? You assume that all planets are equally likely, then predict (based on Kepler's bias) what that distribution of planets would look like to Kepler, then you look at what Kepler actually found and note the differences. Result? Sub-Neptune/Super-Earths (which our solar system lacks) appear to be more common than Earths, and much more common that Jupiters/Saturns. Neptunes are slightly more common than Jupiter/Saturns. Earth-likes (Earth/Venus) are not particularly rare. (Sub-Earths (Mars/Mercury) are still too hard to find to draw a meaningful conclusions.) It looks like there's a weird pattern to the size of sub-Jupiters, they tend to congregate around certain values. Most common are around 2-3 Earth-radii, about 20% of stars. A sharp drop off above 3 Earth-radii (Neptune/Uranus are around 4.) But also a weird drop around 1.8. Then an increase to the next most common value, 1.3 or so Earth-radii, about 10-15% of stars. Then another dip around 1.2 E(r). Then 1 Earth-radius, about 6% of stars. So Earths aren't the most likely, but they are common as muck. One of the three most common sizes of planets. Pretty mundane, you might say. Other results? Every multi-planet system seems to be fairly unique. Some are dominated by large planets, most by small planets, some have a mix. Some have large outers, small inners, some alternate large/small. So you could say that the Solar System is unique. Or that it's mundane. Depending on how you look at it. Absence of a pattern is the pattern. Definitely not what we were expecting. And planets in multi-planet systems are typically distributed across what we think is the habitable zone. It's rare to find a system orbiting entirely within, or entirely without the habitable zone. No papers, but some images that popped up easily... #### Paul451 • Full Member • Posts: 1383 • Australia • Liked: 679 • Likes Given: 575 ##### Re: General SETI Thread « Reply #154 on: 01/29/2018 09:55 PM » Oops, missed this one. In my experience the Mediocrity Principle is usually invoked to argue against the idea that life (let's focus on sentient life in this case) is rare in the Universe. I have never seen it used to argue that other sentient life should be fairly similar to us. It applies to everything. It's just the baseline assumption behind any traits you are measuring. Any traits. It's not a SETI thing. I have never seen it used to argue that other sentient life should be fairly similar to us. They should neither be very like us, nor very unlike us. On a bell curve of key traits, we shouldn't be exactly in the middle, but we certainly shouldn't be out off the end of the curve. OTOH, someone has to be. So measure enough traits and we'll be in the heart of the bell-curve on most of them, on the fringes of a few. That's all the Mediocrity Principle is saying. But it means that when someone shouts "Why should They be like Us!" The answer is, "Why shouldn't they?" Because neither has preference. « Last Edit: 01/29/2018 09:56 PM by Paul451 » #### ExoExplorer • Member • Posts: 15 • Liked: 2 • Likes Given: 2 ##### Re: General SETI Thread « Reply #155 on: 02/04/2018 07:35 PM » Given their activity when young, I lean towards the view that planets around M-dwarfs are less likely to be habitable due to atmosphere / volatiles being stripped. Some might be habitable, but this depends on formation models and the initial volatile fraction ... --- Tony In fact, recent water loss modelings on planets around M-dwarfs found the lost amount during PMS is rather insignificant. Energy-limited formula predicts no more than a few Earth oceans would be lost. The planet mantle also has the potential to store tens of Earth oceans of water and degasses it back to surface at later time. Earth was assembled from giant impacts during the first 100 Myr. Each impact was strong enough to melt the mantle and form magma ocean lasting for several Myr, so Earth also spent a lot of time in runaway greenhouse state during the first 100 Myr. The young sun emitted strong XUV and stellar wind that were comparable to or even stronger than MS M-dwarfs, but no evidence supports that Earth has lost a large amount of volatile. I lean towards agreeing with you. Stripping of atmospheres, combined with tidal lock. While I know that some models suggest that tidal lock and backside freezout is not a big problem if the atmosphere is thick enough, it still erases quite a bit of the habitable parameter space (i.e., if the atmosphere is not thick enough). Combine this with atmospheric erosion and the lack of a strong magnetic field due to slow, locked rotation (further helping with that atmospheric erosion) and we end up in a situation where most rocky planets around M-dwarfs would be poor in volatiles. There might be caveats (e.g., the low density of some of the Trappist-1 planets, although within large errors), and perhaps habitability doesn't really need an atmosphere (-> Europa, Enceladus), but at least Earth-like planets will have a hard time to survive long enough to come up with complex life around an M-dwarf. N2 is resistant to atmospheric collapse (condensing on the dark side). Earth-like atmosphere or 1 bar of N2 is already enough to avoid condensation in the most part of habitable-zone. Indeed, lack of planetary magnetic field poses a threat to habitable planets around M-dwarfs, but the erosion would take at much longer timescale, so it can be replenished through tectonic and volcanic outgassing. The indication of CO2 atmosphere on TRAPPIST-1b observed by Spitzer, if confirmed, would be the evidence of volcanic outgassing secondary atmosphere. There are actually a few advantages. Tidal locking can extend the habitable-zone by weakening Coriolis force and increasing dayside albedo, so the planets at much closer distance can still possess moderate surface temperature. Tidal heating can provide extra energy and extend the lifetime of geological cycles. M-dwarf planets are much less susceptible to snowball, glaciation and limit cycle (very unstable climate), because M-dwarfs emit much light at near-IR wavelengths. The low-density nature of TRAPPIST-1 planets, if confirmed, implies they have volatile mass fractions up to a few to tens percent, equivalent to hundreds of Earth oceans (Earth has only ~0.1%). It is debatable that such volatile-rich planets can be habitable. In fact, a planet with Earth-like volatile is indistinguishable from a pure rock planet based on today's technology and radius-mass chart. « Last Edit: 02/06/2018 12:17 AM by ExoExplorer » #### Dao Angkan • Full Member • Posts: 217 • Liked: 63 • Likes Given: 35 ##### Re: General SETI Thread « Reply #156 on: 02/04/2018 10:52 PM » Why would the Coriolis force be significant? Surely in tidally locked planets then the coriolis force would be insignificant. #### ExoExplorer • Member • Posts: 15 • Liked: 2 • Likes Given: 2 ##### Re: General SETI Thread « Reply #157 on: 02/05/2018 12:03 AM » Atmospheric circulation depends much on the Coriolis force. Strong force would make the clouds banded and distribute them evenly. In contrast, weak force would cause strong rising on the dayside and descending on the nightside. In the later case, optical convective clouds form and cover much area of dayside. They cool the surface down by reflecting over half of radiation back to space. #### CuddlyRocket ##### Re: General SETI Thread « Reply #158 on: 02/05/2018 07:38 PM » Why would the Coriolis force be significant? Surely in tidally locked planets then the coriolis force would be insignificant. Tidally locked planets still spin - once per year, in fact! The significance of the Coriolis force for a tidally locked planet therefore depends on the length of its year. For the seven planets of the TRAPPIST-1 system, the year ranges between 1.5 and 18.8 Earth days. For the innermost planet, the Coriolis force would seem to be roughly as significant as it is on Earth (assuming it has an atmosphere that is!). #### jebbo • Full Member • Posts: 585 • Cambridge, UK • Liked: 235 • Likes Given: 224 ##### Re: General SETI Thread « Reply #159 on: 02/05/2018 07:56 PM » Earth was assembled from giant impacts during the first 100 Myr. Each impact was strong enough to melt the mantle and form magma ocean lasting for several Myr, so Earth also spent a lot of time in runaway greenhouse state during the first 100 Myr. The young sun emitted strong XUV and stellar wind that were comparable to or even stronger than PMS M-dwarfs, but no evidence supports that Earth has lost a large amount of volatile. Figure 1 of https://arxiv.org/abs/1411.7412 suggests otherwise, by large factors. --- Tony « Last Edit: 02/05/2018 08:15 PM by jebbo » #### ExoExplorer • Member • Posts: 15 • Liked: 2 • Likes Given: 2 ##### Re: General SETI Thread « Reply #160 on: 02/06/2018 12:18 AM » Figure 1 of https://arxiv.org/abs/1411.7412 suggests otherwise, by large factors. --- Tony My mistake, I meant to say it was comparable to MS m-dwarfs, not PMS. #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #161 on: 02/07/2018 07:50 PM » A search for technosignatures from 14 planetary systems in the Kepler field with the Green Bank Telescope at 1.15-1.73 GHz Quote Analysis of Kepler mission data suggests that the Milky Way includes billions of Earth-like planets in the habitable zone of their host star. Current technology enables the detection of technosignatures emitted from a large fraction of the Galaxy. We describe a search for technosignatures that is sensitive to Arecibo-class transmitters located within ~450 ly of Earth and transmitters that are 1000 times more effective than Arecibo within ~14 000 ly of Earth. Our observations focused on 14 planetary systems in the Kepler field and used the L-band receiver (1.15-1.73 GHz) of the 100 m diameter Green Bank Telescope. Each source was observed for a total integration time of 5 minutes. We obtained power spectra at a frequency resolution of 3 Hz and examined narrowband signals with Doppler drift rates between +/-9 Hz s-1. We flagged any detection with a signal-to-noise ratio in excess of 10 as a candidate signal and identified approximately 850 000 candidates. Most (99%) of these candidate signals were automatically classified as human-generated radio-frequency interference (RFI). A large fraction (>99%) of the remaining candidate signals were also flagged as anthropogenic RFI because they have frequencies that overlap those used by global navigation satellite systems, satellite downlinks, or other interferers detected in heavily polluted regions of the spectrum. All 19 remaining candidate signals were scrutinized and none could be attributed to an extraterrestrial source. https://arxiv.org/abs/1802.01081 #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #162 on: 02/09/2018 06:47 AM » NASA Should Start Funding SETI Again Quote The search for extraterrestrial intelligence should be a part of the agency’s Astrobiology mission—but thanks to a 1993 law, it’s not https://blogs.scientificamerican.com/observations/nasa-should-start-funding-seti-again/ #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #163 on: 02/18/2018 08:41 PM » Is Humanity Ready for the Discovery of Alien Life? Quote Most Americans would probably be thrilled to learn extraterrestrials (intelligent or not) exist. Other nationalities beg to differ https://www.scientificamerican.com/article/is-humanity-ready-for-the-discovery-of-alien-life/ #### RotoSequence • Full Member • Posts: 906 • Liked: 648 • Likes Given: 829 ##### Re: General SETI Thread « Reply #164 on: 02/23/2018 07:41 AM » https://arxiv.org/abs/1802.07723 Quote Possible Photometric Signatures of Moderately Advanced Civilizations: The Clarke Exobelt Hector Socas-Navarro (Submitted on 21 Feb 2018) This paper puts forward a possible new indicator for the presence of moderately advanced civilizations on transiting exoplanets. The idea is to examine the region of space around a planet where potential geostationary or geosynchronous satellites would orbit (herafter, the Clarke exobelt). Civilizations with a high density of devices and/or space junk in that region, but otherwise similar to ours in terms of space technology (our working definition of "moderately advanced"), may leave a noticeable imprint on the light curve of the parent star. The main contribution to such signature comes from the exobelt edge, where its opacity is maximum due to geometrical projection. Numerical simulations have been conducted for a variety of possible scenarios. In some cases, a Clarke exobelt with a fractional face-on opacity of ~1E-4 would be easily observable with existing instrumentation. Simulations of Clarke exobelts and natural rings are used to quantify how they can be distinguished by their light curve. #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #165 on: 03/15/2018 06:46 AM » #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #166 on: 04/04/2018 08:11 PM » A Cloaking Device for Transiting Planets Quote The transit method is presently the most successful planet discovery and characterization tool at our disposal. Other advanced civilizations would surely be aware of this technique and appreciate that their home planet's existence and habitability is essentially broadcast to all stars lying along their ecliptic plane. We suggest that advanced civilizations could cloak their presence, or deliberately broadcast it, through controlled laser emission. Such emission could distort the apparent shape of their transit light curves with relatively little energy, due to the collimated beam and relatively infrequent nature of transits. We estimate that humanity could cloak the Earth from Kepler-like broadband surveys using an optical monochromatic laser array emitting a peak power of about 30 MW for roughly 10 hours per year. A chromatic cloak, effective at all wavelengths, is more challenging requiring a large array of tunable lasers with a total power of approximately 250 MW. Alternatively, a civilization could cloak only the atmospheric signatures associated with biological activity on their world, such as oxygen, which is achievable with a peak laser power of just around 160 kW per transit. Finally, we suggest that the time of transit for optical SETI is analogous to the water-hole in radio SETI, providing a clear window in which observers may expect to communicate. Accordingly, we propose that a civilization may deliberately broadcast their technological capabilities by distorting their transit to an artificial shape, which serves as both a SETI beacon and a medium for data transmission. Such signatures could be readily searched in the archival data of transit surveys. https://arxiv.org/abs/1603.08928 #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #167 on: 04/10/2018 08:38 PM » Interstellar communication. X. The colors of optical SETI Michael Hippke (Submitted on 4 Apr 2018) It has recently been argued from a laser engineering point of view that there are only a few magic colors for optical SETI. These are primarily the Nd:YAG line at 1064 nm and its second harmonic 532.1 nm. Next best choices would be the sum frequency and/or second harmonic generation of Nd:YAG and Nd:YLF laser lines, 393.8 nm (near Fraunhofer CaK), 656.5 nm (Hα) and 589.1 nm (NaD2). In this paper, we examine the interstellar extinction, atmospheric transparency and scintillation, as well as noise conditions for these laser lines. For strong signals, we find that optical wavelengths are optimal for distances d≲kpc. Nd:YAG at λ=1,064nm is a similarly good choice, within a factor of two, under most conditions and out to d≲3kpc. For weaker transmitters, where the signal-to-noise ratio with respect to the blended host star is relevant, the optimal wavelength depends on the background source, such as the stellar type. Fraunhofer spectral lines, while providing lower stellar background noise, are irrelevant in most use cases, as they are overpowered by other factors. Laser-pushed spaceflight concepts, such as "Breakthrough Starshot", would produce brighter and tighter beams than ever assumed for OSETI. Such beamers would appear as naked eye stars out to kpc distances. If laser physics has already matured and converged on the most efficient technology, the laser line of choice for a given scenario (e.g., Nd:YAG for strong signals) can be observed with a narrow filter to dramatically reduce background noise, allowing for large field-of-view observations in fast surveys. https://arxiv.org/abs/1804.01249 #### philw1776 • Full Member • Posts: 1017 • Seacoast NH • Liked: 610 • Likes Given: 288 ##### Re: General SETI Thread « Reply #168 on: 04/10/2018 08:58 PM » Interstellar communication. X. The colors of optical SETI Michael Hippke (Submitted on 4 Apr 2018) It has recently been argued from a laser engineering point of view that there are only a few magic colors for optical SETI. These are primarily the Nd:YAG line at 1064 nm and its second harmonic 532.1 nm. Next best choices would be the sum frequency and/or second harmonic generation of Nd:YAG and Nd:YLF laser lines, 393.8 nm (near Fraunhofer CaK), 656.5 nm (Hα) and 589.1 nm (NaD2). In this paper, we examine the interstellar extinction, atmospheric transparency and scintillation, as well as noise conditions for these laser lines. For strong signals, we find that optical wavelengths are optimal for distances d≲kpc. Nd:YAG at λ=1,064nm is a similarly good choice, within a factor of two, under most conditions and out to d≲3kpc. For weaker transmitters, where the signal-to-noise ratio with respect to the blended host star is relevant, the optimal wavelength depends on the background source, such as the stellar type. Fraunhofer spectral lines, while providing lower stellar background noise, are irrelevant in most use cases, as they are overpowered by other factors. Laser-pushed spaceflight concepts, such as "Breakthrough Starshot", would produce brighter and tighter beams than ever assumed for OSETI. Such beamers would appear as naked eye stars out to kpc distances. If laser physics has already matured and converged on the most efficient technology, the laser line of choice for a given scenario (e.g., Nd:YAG for strong signals) can be observed with a narrow filter to dramatically reduce background noise, allowing for large field-of-view observations in fast surveys. https://arxiv.org/abs/1804.01249 Impressive. Any back of the envelope calcs on the beam width at varied distances 1pc to 1kpc? “When it looks more like an alien dreadnought, that’s when you know you’ve won.” #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #169 on: 04/10/2018 10:05 PM » Interstellar communication. X. The colors of optical SETI Michael Hippke (Submitted on 4 Apr 2018) It has recently been argued from a laser engineering point of view that there are only a few magic colors for optical SETI. These are primarily the Nd:YAG line at 1064 nm and its second harmonic 532.1 nm. Next best choices would be the sum frequency and/or second harmonic generation of Nd:YAG and Nd:YLF laser lines, 393.8 nm (near Fraunhofer CaK), 656.5 nm (Hα) and 589.1 nm (NaD2). In this paper, we examine the interstellar extinction, atmospheric transparency and scintillation, as well as noise conditions for these laser lines. For strong signals, we find that optical wavelengths are optimal for distances d≲kpc. Nd:YAG at λ=1,064nm is a similarly good choice, within a factor of two, under most conditions and out to d≲3kpc. For weaker transmitters, where the signal-to-noise ratio with respect to the blended host star is relevant, the optimal wavelength depends on the background source, such as the stellar type. Fraunhofer spectral lines, while providing lower stellar background noise, are irrelevant in most use cases, as they are overpowered by other factors. Laser-pushed spaceflight concepts, such as "Breakthrough Starshot", would produce brighter and tighter beams than ever assumed for OSETI. Such beamers would appear as naked eye stars out to kpc distances. If laser physics has already matured and converged on the most efficient technology, the laser line of choice for a given scenario (e.g., Nd:YAG for strong signals) can be observed with a narrow filter to dramatically reduce background noise, allowing for large field-of-view observations in fast surveys. https://arxiv.org/abs/1804.01249 Impressive. Any back of the envelope calcs on the beam width at varied distances 1pc to 1kpc? Actually it was who the author was caught my attention. #### LouScheffer • Full Member • Posts: 1821 • Liked: 2342 • Likes Given: 253 ##### Re: General SETI Thread « Reply #170 on: 04/12/2018 05:41 PM » Interstellar communication. X. The colors of optical SETI Michael Hippke (Submitted on 4 Apr 2018) It has recently been argued from a laser engineering point of view that there are only a few magic colors for optical SETI. These are primarily the Nd:YAG line at 1064 nm and its second harmonic 532.1 nm. Next best choices would be the sum frequency and/or second harmonic generation of Nd:YAG and Nd:YLF laser lines, 393.8 nm (near Fraunhofer CaK), 656.5 nm (Hα) and 589.1 nm (NaD2). In this paper, we examine the interstellar extinction, atmospheric transparency and scintillation, as well as noise conditions for these laser lines. For strong signals, we find that optical wavelengths are optimal for distances d≲kpc. Nd:YAG at λ=1,064nm is a similarly good choice, within a factor of two, under most conditions and out to d≲3kpc. For weaker transmitters, where the signal-to-noise ratio with respect to the blended host star is relevant, the optimal wavelength depends on the background source, such as the stellar type. Fraunhofer spectral lines, while providing lower stellar background noise, are irrelevant in most use cases, as they are overpowered by other factors. Laser-pushed spaceflight concepts, such as "Breakthrough Starshot", would produce brighter and tighter beams than ever assumed for OSETI. Such beamers would appear as naked eye stars out to kpc distances. If laser physics has already matured and converged on the most efficient technology, the laser line of choice for a given scenario (e.g., Nd:YAG for strong signals) can be observed with a narrow filter to dramatically reduce background noise, allowing for large field-of-view observations in fast surveys. https://arxiv.org/abs/1804.01249 This is based on Which colors would extraterrestrial civilizations use to transmit signals?: The “magic wavelengths” for optical SETI which in my opinion is a very weak argument. Just because Nd:YAG lasers are the best for us now does not mean they are the best for everyone, for all time. Other civilizations may well have discovered different combinations of compunds that are similarly efficient. Furthermore, there are lots of possible technology developments in metamaterials, quantum waveguides, and so on, that could lead to arbitrary wavelengths. Also, for long term use, it might be better to pick a technology that can be pumped directly by radiation from the sun, where the easy availability of free power might be cheaper for a given power output, even if the efficiency is lower. Overall, I think it's way premature to limit our searches to only the laser lines we would pick now. #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #171 on: 04/12/2018 07:56 PM » Spot the Doctor Who reference. The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record? Quote If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event. http://xxx.lanl.gov/abs/1804.03748 #### LouScheffer • Full Member • Posts: 1821 • Liked: 2342 • Likes Given: 253 ##### Re: General SETI Thread « Reply #172 on: 04/13/2018 01:31 AM » Spot the Doctor Who reference. The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record? Quote If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event. http://xxx.lanl.gov/abs/1804.03748 Some things we do to geology, like cement filled holes of old oil wells, a meter wide and several km long, perpendicular to the rock layers, should survive for geological times and be unambiguously constructed and not natural. Finding even one would show a previous civilization. #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### General SETI Thread « Reply #173 on: 04/13/2018 06:38 AM » Spot the Doctor Who reference. The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record? Quote If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event. http://xxx.lanl.gov/abs/1804.03748 Some things we do to geology, like cement filled holes of old oil wells, a meter wide and several km long, perpendicular to the rock layers, should survive for geological times and be unambiguously constructed and not natural. Finding even one would show a previous civilization. No guarantee any previous civilisation would extract oil and nor that such activities would last over geological times especially if only in a limited area(s). « Last Edit: 04/13/2018 06:39 AM by Star One » #### missinglink • Full Member • Posts: 123 • Liked: 18 • Likes Given: 107 ##### Re: General SETI Thread « Reply #174 on: 04/13/2018 08:06 PM » I've been told that the zillions of tons of coal burned since the start of the industrial revolution have deposited a thin layer of soot* in the geological record that is distinguishable from the outcome of natural processes. Hard to imagine a technological civilization that would skip over using coal as fuel altogether. *Think of it as a "shadow out of time", heh heh. #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### General SETI Thread « Reply #175 on: 04/13/2018 08:08 PM » The Breakthrough Listen Search for Intelligent Life: Wide-bandwidth Digital Instrumentation for the CSIRO Parkes 64-m Telescope Breakthrough Listen is a ten-year initiative to search for signatures of technologies created by extraterrestrial civilizations at radio and optical wavelengths. Here, we detail the digital data recording system deployed for Breakthrough Listen observations at the 64-m aperture CSIRO Parkes Telescope in New South Wales, Australia. The recording system currently implements two recording modes: a dual-polarization, 1.125~GHz bandwidth mode for single beam observations, and a 26-input, 308~MHz bandwidth mode for the 21-cm multibeam receiver. The system is also designed to support a 3~GHz single-beam mode for the forthcoming Parkes ultra-wideband feed. In this paper, we present details of the system architecture, provide an overview of hardware and software, and present initial performance results. https://arxiv.org/abs/1804.04571 « Last Edit: 04/13/2018 08:09 PM by Star One » #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #176 on: 04/13/2018 08:31 PM » https://twitter.com/jeff_foust/status/984857830615330816?s=20 Quote Those at #Discuss2018 may find of interest this language from Sec. 311 of the authorization bill supporting partnerships “to search for technosignatures, such as radio transmissions” from any life in the universe. #### tea monster • Full Member • Posts: 329 • Across the Universe • Liked: 143 • Likes Given: 47 ##### Re: General SETI Thread « Reply #177 on: 04/15/2018 11:35 AM » Coal and Oil didn't exist back then. We are driving around using oil that is between 60 and 100 million years old*. The Silurian period was over 400M years old. If they used wood, then it would just be attributed to forest fires at the time. Maybe look for deposits of depleted uranium at that point in the fossil record. * - https://phys.org/news/2005-05-world-age-oil.html « Last Edit: 04/15/2018 11:52 AM by tea monster » #### TakeOff • Full Member • Posts: 379 • Liked: 76 • Likes Given: 107 ##### Re: General SETI Thread « Reply #178 on: 04/15/2018 02:34 PM » It looks like there's a weird pattern to the size of sub-Jupiters, they tend to congregate around certain values. Most common are around 2-3 Earth-radii, about 20% of stars. A sharp drop off above 3 Earth-radii (Neptune/Uranus are around 4.) But also a weird drop around 1.8. Then an increase to the next most common value, 1.3 or so Earth-radii, about 10-15% of stars. Then another dip around 1.2 E(r). Then 1 Earth-radius, about 6% of stars. So Earths aren't the most likely, but they are common as muck. One of the three most common sizes of planets. Pretty mundane, you might say. Erik Petigura has a potential explanation. Basically the stellar wind removes a hydrogen envelope more quickly the more depleted it gets. So there are planets with big envelopes and planets without any envelope, but only briefly do planets have a small envelope. Thus the gap. https://webcast.stsci.edu/webcast/detail.xhtml?talkid=6131&parent=1 #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #179 on: 04/18/2018 06:10 PM » Spot the Doctor Who reference. The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record? Quote If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event. http://xxx.lanl.gov/abs/1804.03748 More from the author of the paper’s authors. https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/ #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #180 on: 04/23/2018 07:52 PM » Could an Industrial Prehuman Civilization Have Existed on Earth Before Ours? Quote Today, less than 1 percent of Earth’s surface is urbanized, and the chance that any of our great cities would remain over tens of millions of years is vanishingly low, says Jan Zalasiewicz, a geologist at the University of Leicester in England. A metropolis’s ultimate fate, he notes, mostly depends on whether the surrounding surface is subsiding (to be locked in rock) or rising (to be eroded away by rain and wind). “New Orleans is sinking; San Francisco is rising,” he says. The French Quarter, it seems, has much better chances of entering the geologic record than Haight–Ashbury. Quote “After a couple of million years,” Frank says, “the chances are that any physical reminder of your civilization has vanished, so you have to search for things like sedimentary anomalies or isotopic ratios that look off.” The shadows of many prehuman civilizations could, in principle, lurk hidden in such subtleties. Quote Taking all this into consideration, what remains is a menu of diffuse long-lived tracers including fossil fuel combustion residues (carbon, primarily), evidence of mass extinctions, plastic pollutants, synthetic chemical compounds not found in nature and even transuranic isotopes from nuclear fission. In other words, what we would need to look for in the geologic record are the same distinctive signals that humans are laying down right now. Quote “I find it amazing that no one had worked all this out before, and I’m really glad that somebody has taken a closer look at it,” says Pennsylvania State University astronomer Jason Wright, who last year published “a fluffy little paper” exploring the counterintuitive notion that the best place to find evidence of any of Earth’s putative prehuman civilizations may well be off-world. If, for instance, dinosaurs built interplanetary rockets, presumably some remnants of that activity might remain preserved in stable orbits or on the surfaces of more geologically inert celestial bodies such as the moon. Quote Wright also acknowledges the potential for this work to be misinterpreted. “Of course, no matter what, this is going to be interpreted as ‘Astronomers Say Silurians Might Have Existed,’ even though the premise of this work is that there is no such evidence,” he says. “Then again, absence of evidence is not evidence of absence.” https://www.scientificamerican.com/article/could-an-industrial-prehuman-civilization-have-existed-on-earth-before-ours/ #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #181 on: 04/24/2018 08:55 PM » SETI with Gaia: The observational signatures of nearly complete Dyson spheres Quote A star enshrouded in a Dyson sphere with high covering fraction may manifest itself as an optically subluminous object with a spectrophotometric distance estimate significantly in excess of its parallax distance. Using this criterion, the Gaia mission will in coming years allow for Dyson-sphere searches that are complementary to searches based on waste-heat signatures at infrared wavelengths. A limited search of this type is also possible at the current time, by combining Gaia parallax distances with spectrophotometric distances from ground-based surveys. Here, we discuss the merits and shortcomings of this technique and carry out a limited search for Dyson-sphere candidates in the sample of stars common to Gaia Data Release 1 and RAVE Data Release 5. We find that a small fraction of stars indeed display distance discrepancies of the type expected for nearly complete Dyson spheres. To shed light on the properties of objects in this outlier population, we present follow-up high-resolution spectroscopy for one of these stars, the late F-type dwarf TYC 6111-1162-1. The spectrophotometric distance of this object is about twice that derived from its Gaia parallax, and there is no detectable infrared excess. While our analysis largely confirms the stellar parameters and the spectrophotometric distance inferred by RAVE, a plausible explanation for the discrepant distance estimates of this object is that the astrometric solution has been compromised by an unseen binary companion, possibly a rather massive white dwarf (≈1 M⊙). This scenario can be further tested through upcoming Gaia data releases. https://arxiv.org/abs/1804.08351 #### jebbo • Full Member • Posts: 585 • Cambridge, UK • Liked: 235 • Likes Given: 224 ##### Re: General SETI Thread « Reply #182 on: 04/26/2018 05:33 PM » Don't think the discrepancy for TYC 6111-1162-1 holds up given Gaia DR2, which has a significantly lower parallax. The spectroscopic and astrometric are now only ~1.5 sigma apart. #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### General SETI Thread « Reply #183 on: 04/27/2018 08:14 PM » Another fascinating article on the Silurian Hypothesis. Quote Ancient aliens. Devious dinosaurs. Benevolent Atlanteans. Could such legendary civilisations have left any trace behind that would survive the eons? Archaeologists are certain: we have … so why not them? http://www.adelaidenow.com.au/news/special-features/in-depth/silurian-hypothesis-what-if-humans-were-not-earths-first-civilisation/news-story/8fdb004d4d52b7612acbaec711e280c8 « Last Edit: 04/27/2018 08:16 PM by Star One » #### Star One • Senior Member • Posts: 9330 • UK • Liked: 1656 • Likes Given: 183 ##### Re: General SETI Thread « Reply #184 on: 05/09/2018 07:32 PM » Congress Is Quietly Nudging NASA to Look for Aliens Quote That could soon change. Lawmakers in the House of Representatives recently proposed legislation for nasa’s future that includes some intriguing language. The space agency, the bill recommends, should spend$10 million on the “search for technosignatures, such as radio transmissions” in the next two fiscal years.

The House bill—should it survive a vote in the House and passage in the Senate—can only make recommendations for how agencies should use federal funding. But for seti researchers like Tarter, the fact that it even exists is thrilling. It’s the first time congressional lawmakers have proposed using federal cash to fund seti in 25 years.

https://www.theatlantic.com/amp/article/558512/

#### Star One

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« Reply #185 on: 05/10/2018 07:22 PM »
NASA Awards Grants for Research into Life in Universe

NASA has awarded five-year grants, each approximately \$8 million, to three research teams that will study the origins, evolution, distribution and future of life in the universe.

“With NASA’s Transiting Exoplanet Survey Satellite on its way to discover new worlds around our nearest stellar neighbors, Cassini’s discovery of the ingredients necessary for life in Enceladus’s plumes, and with Europa Clipper and Mars 2020 on the horizon, these research teams will provide the critical interdisciplinary expertise needed to help interpret data from these missions and future astrobiology-focused missions,” said NASA Chief Scientist Jim Green.

The interdisciplinary teams will become members of the NASA Astrobiology Institute (NAI), headquartered at the agency’s Ames Research Center in Silicon Valley, California.

The selected teams are:

Evolution of Nanomachines in Geospheres and Microbial Ancestors (ENIGMA)

Rutgers University

New Brunswick, New Jersey

Led by Professor Paul Falkowski, the ENIGMA team will investigate how proteins evolved to become the catalysts of life on Earth by looking at prebiotic molecules and enzymes that are ancestral and common across many types of microbes.

The Astrobiology Center for Isotopologue Research (ACIR)

Pennsylvania State University, University Park

ACIR, led by Professor Kate Freeman, will address how the features of elements within molecules reveal the origins and history of organic compounds, from compounds that arrived from planetary environments to those that were derived from metabolic systems, using cutting-edge observational and computational tools.

NASA’s Jet Propulsion Laboratory (JPL)

Dr. Rosaly Lopes will lead research at JPL focusing on Saturn’s largest moon, Titan, to address what habitable environments may exist on the moon and what potential signatures of life would be expected, using data from the Cassini-Huygens mission. These data cover a wide swath of the moon, from beneath its surface all the way up through its thick atmosphere.

“The intellectual scope of astrobiology is vast, from understanding how our planet became habitable and inhabited, to understanding how life has adapted to Earth’s harshest environments, to exploring other worlds with the most advanced technologies to search for signs of life,” said Mary Voytek, director of the Astrobiology Program at NASA Headquarters. “The new teams will complement our existing teams to cover breadth of astrobiology, and by coming together in the NAI, they will make the connections between disciplines and organizations that stimulate fundamental scientific advances.”

“We are delighted to welcome these three new NAI teams into the Institute family and look forward to the important work that they will accomplish over the time of their awards,” said NAI Director Penelope Boston. “Our existing teams are waiting to explore overlapping interests with the new project teams and the potential for even greater exchange of information, inspiration, and synergy.”

The NAI serves a vital role in advancing the goals of the NASA Astrobiology Program, with a focus on seeking the answers to these fundamental questions: How does life begin and evolve? Is there life beyond Earth and, if so, how can we detect it? What is the future of life on Earth and beyond?

https://nai.nasa.gov/

#### Star One

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« Reply #186 on: 05/18/2018 03:28 PM »

#### Star One

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« Reply #187 on: 05/20/2018 08:24 PM »

Expanding cosmological civilizations on the back of an envelope

Quote
We present a simplified description of expansionistic life in the standard relativistic cosmology. The resulting model is exactly integrable, yielding a simple set of predictive formulas. This allows one to quickly propose new scenarios for the life appearance rate and the dominant expansion speed and evaluate the observable consequences. These include the expected number and angular size of visible expanding domains, the total eclipsed fraction of the sky, and the life-saturated fraction of the universe. We also propose a simple anthropic bound on observable quantities, as a function of the dominant expansion velocity alone. The goal is to create a simple and intuition-building tool for use in the context of cosmology, extragalactic SETI, and futures studies. We discuss the general predictions of this framework, including conditions giving rise to an "extragalactic Fermi paradox," in which zero civilizations are visible beyond the Milky Way. This can occur even if a substantial fraction of the universe is already saturated with ambitious life.

https://arxiv.org/abs/1805.06329

#### Star One

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« Reply #188 on: 06/13/2018 07:41 PM »

Anders Sandberg, Eric Drexler, Toby Ord

Quote
The Fermi paradox is the conflict between an expectation of a high {\em ex ante} probability of intelligent life elsewhere in the universe and the apparently lifeless universe we in fact observe. The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation, which suggest that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty regarding highly uncertain parameters. We examine these parameters, incorporating models of chemical and genetic transitions on paths to the origin of life, and show that extant scientific knowledge corresponds to uncertainties that span multiple orders of magnitude. This makes a stark difference. When the model is recast to represent realistic distributions of uncertainty, we find a substantial {\em ex ante} probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it. This result dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe.

https://arxiv.org/abs/1806.02404

I like the way they try and find a way to supplant an equation that has a lot of guesses but using a whole other bunch of guesses. Because at the end that’s all any of it is.
« Last Edit: 06/13/2018 09:40 PM by Star One »

#### RotoSequence

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