Author Topic: What If Humanity Is Among The First Spacefaring Civilizations?  (Read 24927 times)

Offline sanman

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The ones closer to us, if they exist,  will likely be alive and the ones coming from far away will be more likely to be dead when they arrive.

Space travel is never trivial, unless you go into science fictional levels of technology where you snap your fingers and a spaceship appears and you can travel close to the speed of light. But I suppose we're talking about reasonable, "known to us" means of propulsion as well as manufacturing and outfitting (i.e. no magical force fields to contain hull breaches).

The longer they have to travel (just imagine sitting on top of each other for 1000 years, classes/factions are going to form, in-ship wars may be inevitable) the more likely it is that some technical failure, sabotage, uprising or other stuff happens that damages their ship and renders it uninhabitable.

So, either a long distance species coming to us is extremely peaceful (towards each other and probably towards outsiders) or dead.

What if they're self-replicating Von Neumann swarms?


Offline M.E.T.

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

« Last Edit: 11/30/2022 03:15 am by M.E.T. »

Offline Yiosie

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

From what I gather about the grabby aliens hypothesis, it is specifically designed to address the question of why humans have appeared so early in the universe's existence, 13.8 billion years in, when the average star in the universe will last ~5 trillion years and it is vastly more likely for advanced life to appear later rather than sooner by the hard-steps power law model of the origin of advanced life. It states that if we assume that human civilization is not special in appearing so early (Copernican principle and all), then there must be something that prevents civilizations like ours from appearing and observing the universe like we do in those trillions of years of distant future; that "something" is grabby aliens, which drastically change their stellar environments and prevent the emergence of indigenous alien civilizations within their sphere of influence.

Because we don't observe the kind of obvious stellar engineering activity that defines "grabby aliens", the appearance rate of these types of alien civilizations is highly constrained. Robin Hanson, who proposed and wrote the mathematical model behind this hypothesis, states the following here:

Quote
Our recent analysis suggests that they appear at random stars roughly once per million galaxies, and then expand at roughly half the speed of light. Right now, they have filled roughly half of the universe, and if we join them we’ll meet them in roughly a billion years. There may be far more quiet than grabby alien civs out there, but those don’t usually do much or last long, and even the ruins of the nearest are quite far away.

Those are the median values that his model spits out if we assume grabby civilizations both exist and haven't appeared in our light cone yet. So it's not that "the older a civilization is, the farther away from Earth it has to be"; it's that grabby aliens in particular are so rare and expand so fast that it isn't unusual that we don't see them yet (even then, Hanson predicts that over half the universe can currently see obvious alien activity in their night skies; we're just outside those light cones at the moment). Basically, we'll encounter the nearest one in about a billion years, and in under ten billion years every star in the observable universe will be within a grabby civilization. Thus, we observe ourselves appearing near the beginning of the universe's history because civilizations like ours can only appear near the beginning; Copernican principle preserved.

Offline M.E.T.

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

From what I gather about the grabby aliens hypothesis, it is specifically designed to address the question of why humans have appeared so early in the universe's existence, 13.8 billion years in, when the average star in the universe will last ~5 trillion years and it is vastly more likely for advanced life to appear later rather than sooner by the hard-steps power law model of the origin of advanced life. It states that if we assume that human civilization is not special in appearing so early (Copernican principle and all), then there must be something that prevents civilizations like ours from appearing and observing the universe like we do in those trillions of years of distant future; that "something" is grabby aliens, which drastically change their stellar environments and prevent the emergence of indigenous alien civilizations within their sphere of influence.

Because we don't observe the kind of obvious stellar engineering activity that defines "grabby aliens", the appearance rate of these types of alien civilizations is highly constrained. Robin Hanson, who proposed and wrote the mathematical model behind this hypothesis, states the following here:

Quote
Our recent analysis suggests that they appear at random stars roughly once per million galaxies, and then expand at roughly half the speed of light. Right now, they have filled roughly half of the universe, and if we join them we’ll meet them in roughly a billion years. There may be far more quiet than grabby alien civs out there, but those don’t usually do much or last long, and even the ruins of the nearest are quite far away.

Those are the median values that his model spits out if we assume grabby civilizations both exist and haven't appeared in our light cone yet. So it's not that "the older a civilization is, the farther away from Earth it has to be"; it's that grabby aliens in particular are so rare and expand so fast that it isn't unusual that we don't see them yet (even then, Hanson predicts that over half the universe can currently see obvious alien activity in their night skies; we're just outside those light cones at the moment). Basically, we'll encounter the nearest one in about a billion years, and in under ten billion years every star in the observable universe will be within a grabby civilization. Thus, we observe ourselves appearing near the beginning of the universe's history because civilizations like ours can only appear near the beginning; Copernican principle preserved.

All of that still means that billion year old civilizations have to be more than a billion light years away, while 100 million year old civilizations only need to be 100 million light years away. The inverse would mean that the billion year old civilization would have been visible to us for the last 900 million years or so.

So yes, it does mean that older civilizations have to be farther away to make the model work.
« Last Edit: 11/30/2022 09:37 am by M.E.T. »

Offline Yiosie

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

From what I gather about the grabby aliens hypothesis, it is specifically designed to address the question of why humans have appeared so early in the universe's existence, 13.8 billion years in, when the average star in the universe will last ~5 trillion years and it is vastly more likely for advanced life to appear later rather than sooner by the hard-steps power law model of the origin of advanced life. It states that if we assume that human civilization is not special in appearing so early (Copernican principle and all), then there must be something that prevents civilizations like ours from appearing and observing the universe like we do in those trillions of years of distant future; that "something" is grabby aliens, which drastically change their stellar environments and prevent the emergence of indigenous alien civilizations within their sphere of influence.

Because we don't observe the kind of obvious stellar engineering activity that defines "grabby aliens", the appearance rate of these types of alien civilizations is highly constrained. Robin Hanson, who proposed and wrote the mathematical model behind this hypothesis, states the following here:

Quote
Our recent analysis suggests that they appear at random stars roughly once per million galaxies, and then expand at roughly half the speed of light. Right now, they have filled roughly half of the universe, and if we join them we’ll meet them in roughly a billion years. There may be far more quiet than grabby alien civs out there, but those don’t usually do much or last long, and even the ruins of the nearest are quite far away.

Those are the median values that his model spits out if we assume grabby civilizations both exist and haven't appeared in our light cone yet. So it's not that "the older a civilization is, the farther away from Earth it has to be"; it's that grabby aliens in particular are so rare and expand so fast that it isn't unusual that we don't see them yet (even then, Hanson predicts that over half the universe can currently see obvious alien activity in their night skies; we're just outside those light cones at the moment). Basically, we'll encounter the nearest one in about a billion years, and in under ten billion years every star in the observable universe will be within a grabby civilization. Thus, we observe ourselves appearing near the beginning of the universe's history because civilizations like ours can only appear near the beginning; Copernican principle preserved.

All of that still means that billion year old civilizations have to be more than a billion light years away, while 100 million year old civilizations only need to be 100 million light years away. The inverse would mean that the billion year old civilization would have been visible to us for the last 900 million years or so.

So yes, it does mean that older civilizations have to be farther away to make the model work.

That's kind of a natural consequence of the hard-steps model of the development of complex life, rather than for the grabby aliens model? It is very unlikely for each step in the process to occur successfully, so the rate that new advanced lifeforms appear in the universe is one that will increase exponentially over time. The earliest civilizations, if distributed throughout the universe somewhat evenly, would be separated by billions of light years; the more recent ones, filling in the gaps, would be separated by "only" hundreds of millions of light years. Therefore, it isn't unreasonable to expect that the billion year old grabby aliens are over a billion light years away, and 100 million year old ones are hundreds of millions of light years away. Alien civilizations are supposed to be extremely rare after all, and grabby aliens comprise a tiny fraction of the total number of civilizations.

I suppose you could imagine a cosmic Powerball lottery where you can repeatedly choose numbers from 1 to 1 billion indefinitely for each slot (representing the hard steps in the development of complex life), and you only move on to the next slot once you finally guess the right one. The first ones to guess the final slot are freakishly lucky and find themselves alone for a very long time, but the completion rate picks up over time as more and more people reach the final slot and get lucky. The final Powerball number is optional in this scenario, and those who actually attempt it are civilizations that try to become "grabby"; the successful guessers get to spread out until the universe is full, while those who fail become "quiet" civilizations or collapse and don't make much impact on the universe.

Incidentally, the model posits that only about one star in a million galaxies will ever spawn a grabby civilization, so you actually do have to be a little lucky (or unlucky, depending on your point of view) to have another grabby alien civilization spawn within your galactic supercluster before grabby aliens from a neighboring supercluster arrive a billion years later.

Offline markbike528cbx

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…..snip…
So, either a long distance species coming to us is extremely peaceful (towards each other and probably towards outsiders) or dead.

Agree with that assessment, which incidentally simply echoes 'the meek shall inherit...'.
One should also adjust for the sheer improbability of technically intelligent life, with much less than 10,000 years of existence in the at least 1 billion years of life on earth.
I have a T-shirt that says “And the geek shall inherit the earth”.  So meek geeks for the win?

Offline laszlo

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I also wonder if seeing signs of highly advanced aliens is overstated. It assumes that as aliens advance, their artifacts get larger and more visible. What if it's the opposite? We see some of that right here on Earth. Compare the pile of 19th-century explosives it would have taken to completely flatten London and its environs in Queen Victoria's time with a staged thermonuclear weapon that could so the same today to the even larger London. Or compare the size and contents of the RMS Titanic's engine room, all to produce 38 MW to the Raptor 2 which fits on a forklift pallet and produces multiple GW. Or a 1950's 4-story SAGE blockhouse to a modern truck-mounted air-defense control center.

As tech gets better, it gets smaller. Modern computer chips have more transistors than our brains have neurons. Nano machinery is so small that it's invisible. A truly advanced alien may be microscopic, powered by cosmic radiation and manipulating space-time directly with some kind of quantum effectors. They may move have flooded their local space with uncountable numbers of these tiny bodies and be moving their consciousnesses between them at the speed of light. If there are enough of these tiny but highly absorptive creatures out there, we may only "see" them through their net gravitational effects. They could be the explanation for dark matter.

Even if that's not the case, if advanced aliens have moved their tech to the quantum scales, they could be all over the space that we see but still be invisible to us. We could be the primitives standing under the cell towers looking for the giant drums that the civilized folks signal with and wondering where they all are.


Online DanClemmensen

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I also wonder if seeing signs of highly advanced aliens is overstated. It assumes that as aliens advance, their artifacts get larger and more visible. What if it's the opposite? We see some of that right here on Earth. Compare the pile of 19th-century explosives it would have taken to completely flatten London and its environs in Queen Victoria's time with a staged thermonuclear weapon that could so the same today to the even larger London. Or compare the size and contents of the RMS Titanic's engine room, all to produce 38 MW to the Raptor 2 which fits on a forklift pallet and produces multiple GW. Or a 1950's 4-story SAGE blockhouse to a modern truck-mounted air-defense control center.

As tech gets better, it gets smaller. Modern computer chips have more transistors than our brains have neurons. Nano machinery is so small that it's invisible. A truly advanced alien may be microscopic, powered by cosmic radiation and manipulating space-time directly with some kind of quantum effectors. They may move have flooded their local space with uncountable numbers of these tiny bodies and be moving their consciousnesses between them at the speed of light. If there are enough of these tiny but highly absorptive creatures out there, we may only "see" them through their net gravitational effects. They could be the explanation for dark matter.

Even if that's not the case, if advanced aliens have moved their tech to the quantum scales, they could be all over the space that we see but still be invisible to us. We could be the primitives standing under the cell towers looking for the giant drums that the civilized folks signal with and wondering where they all are.
In the case of communications signals specifically, if the SNR is >0 dB, then the signal is inefficient and implies a civilization that is not highly advanced. But a signal with a low SNR is hard to detect unless you know how it was encoded in the first place.

Offline Bob Shaw

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Alien civilisations which transmit on radio, light etc may just be a passing phase before some other methods are embraced (gravity waves, neutrinos, quantum magic). Perhaps Drake is actually conservative, and we're just not aware of the chatter that's out there? I think not.

If Drake is correct, there are a couple of points arising from that even if nobody is using our level of communication technology: firstly, what should we see that implies no formal communicatiion? The answer is simple: pollution, changes in chemistry in stars, odd IR signatures. We don't so far as I know, see any of these so far and this suggests that in fact we may be 'early'. A second point must be that machine civilisations are not time-constrained in the way that organic ones are, and should be able to simply and cheaply colonise *everywhere* over relatively short timescales - and again, we see no signs. It really looks like we are in a universe where intelligence has not yet spread.

Life, of course, is everywhere - but it is highly evolved, perfectly adapted, slime.

Offline tea monster

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We could be the primitives standing under the cell towers looking for the giant drums that the civilized folks signal with and wondering where they all are.
I use a similar analogy. Imagine a curious native islander climbing to the top of the central peak of his known world. He raises his hand to his eyes and squints, hoping to see a wisp of smoke that will reveal that his isn't the only inhabited island. As he peers across the horizon, radio waves from the global civilisation criss-cross through his body.

We haven't sent biologists to any other planet and examined it directly and extensively for life. We have good reason to think it should be everywhere, but we don't really know this. We could be missing something vital.

Offline whitelancer64

*snip*

The answer is simple: pollution, changes in chemistry in stars, odd IR signatures. We don't so far as I know, see any of these so far

*snip*

Life, of course, is everywhere - but it is highly evolved, perfectly adapted, slime.

We haven't had tools powerful and sophisticated enough to potentially pick out such signatures in starlight or in exo-atmospheres until the James Webb Space Telescope.

JWST will tell us whether or not there is life on other planets, and provide an initial data set on how common (or not) it is, within the next 5 years.

Your conclusion is likely correct. I fully expect to see biosignatures of simple life virtually everywhere we look. I'm looking forward to seeing if JWST finds this to be the case.
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Offline sanman

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

But the reason why the grabbies have to be farther away, is because if they weren't, then they'd likely have already grabbed us by now. The older they are, the grabbier they can be, since their engineering capabilities only grow with time, and their Von Neumann swarms have more time to grow in size and voraciousness (provided their own swarms don't swarm back at them)

Why is it that "the simpler alternative is that they’re just not there in the first place" ?? Why is that simpler?
Simpler that they're not there? Or simpler that they're just not grabby?
« Last Edit: 12/01/2022 05:13 am by sanman »

Offline M.E.T.

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

But the reason why the grabbies have to be farther away, is because if they weren't, then they'd likely have already grabbed us by now. The older they are, the grabbier they can be, since their engineering capabilities only grow with time, and their Von Neumann swarms have more time to grow in size and voraciousness (provided their own swarms don't swarm back at them)

Why is it that "the simpler alternative is that they’re just not there in the first place" ?? Why is that simpler?
Simpler that they're not there? Or simpler that they're just not grabby?

That’s a bit like arguing the reason the boogeyman has to be on Easter Island rather in New York is because if he was in New York he would have attacked us by now.

EDIT

If you don’t see any aliens, surely it is simpler to argue they are not there (until evidence proves otherwise), than to contrive an answer where they HAVE to be there, but they all just happen to be at a distance where their age does not allow their light to have reached us yet.

There could be multiple 5 billion year old civilizations, but according to this theory they just happen to all be more than 5 billion light years away. When in reality their distribution should be random, as the Milky Way or Andromeda is just as old as galaxies 5 or 10 billion light years away.
« Last Edit: 12/01/2022 08:12 am by M.E.T. »

Offline Yiosie

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

But the reason why the grabbies have to be farther away, is because if they weren't, then they'd likely have already grabbed us by now. The older they are, the grabbier they can be, since their engineering capabilities only grow with time, and their Von Neumann swarms have more time to grow in size and voraciousness (provided their own swarms don't swarm back at them)

Why is it that "the simpler alternative is that they’re just not there in the first place" ?? Why is that simpler?
Simpler that they're not there? Or simpler that they're just not grabby?

That’s a bit like arguing the reason the boogeyman has to be on Easter Island rather in New York is because if he was in New York he would have attacked us by now.

EDIT

If you don’t see any aliens, surely it is simpler to argue they are not there (until evidence proves otherwise), than to contrive an answer where they HAVE to be there, but they all just happen to be at a distance where their age does not allow their light to have reached us yet.

There could be multiple 5 billion year old civilizations, but according to this theory they just happen to all be more than 5 billion light years away. When in reality their distribution should be random, as the Milky Way or Andromeda is just as old as galaxies 5 or 10 billion light years away.

There's a video on YouTube from one of the co-authors of the paper proposing the grabby aliens hypothesis that shows a 3D simulation of a median scenario in their model:



The first grabby alien civilizations only appear about 6 billions years after the Big Bang due to the lack of heavy elements in Population III and II stars formed in the early universe. After 13.8 billion years, the majority of the observable universe is within a grabby alien civilization, but large gaps still exist where observers would see no obvious sign of aliens in their observable universes. To your point about multiple 5 billion year old civilizations, this particular sim shows only about 8-10 existing grabby alien civs in the observable universe 5 billion years ago; if evenly distributed, their origin points would be separated by over 5 billion light years on average today, and when randomly distributed there would be smaller and large gaps. "Older civilization far, newer civilization closer" is therefore unsurprising, given how incredibly rare grabby aliens are (only 87 appear in total for this particular simulation over the 20 billion years it takes for the observable universe to be full).

The grabby aliens model doesn't "contrive an answer where they HAVE to be there", it hypothesizes the existence of grabby aliens (defined as civilizations that expand quickly and radically modify stars and galaxies for their use) specifically and explicitly to explain why humans have appeared very early in the universe's history without rejecting the Copernican principle: it proposes that we aren't special, and have in fact appeared close to the end of the time in the universe when we could have possibly spawned before the universe is filled. The model then constrains the appearance rate and expansion speeds of these grabby aliens due to the fact that we don't currently observe them.

Of course, everything here assumes that we are not, in fact, extremely special or unique in the timing or presence of our civilization. That we are not alone, and that we have not appeared early due to luck.

Offline M.E.T.

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

But the reason why the grabbies have to be farther away, is because if they weren't, then they'd likely have already grabbed us by now. The older they are, the grabbier they can be, since their engineering capabilities only grow with time, and their Von Neumann swarms have more time to grow in size and voraciousness (provided their own swarms don't swarm back at them)

Why is it that "the simpler alternative is that they’re just not there in the first place" ?? Why is that simpler?
Simpler that they're not there? Or simpler that they're just not grabby?

That’s a bit like arguing the reason the boogeyman has to be on Easter Island rather in New York is because if he was in New York he would have attacked us by now.

EDIT

If you don’t see any aliens, surely it is simpler to argue they are not there (until evidence proves otherwise), than to contrive an answer where they HAVE to be there, but they all just happen to be at a distance where their age does not allow their light to have reached us yet.

There could be multiple 5 billion year old civilizations, but according to this theory they just happen to all be more than 5 billion light years away. When in reality their distribution should be random, as the Milky Way or Andromeda is just as old as galaxies 5 or 10 billion light years away.

There's a video on YouTube from one of the co-authors of the paper proposing the grabby aliens hypothesis that shows a 3D simulation of a median scenario in their model:



The first grabby alien civilizations only appear about 6 billions years after the Big Bang due to the lack of heavy elements in Population III and II stars formed in the early universe. After 13.8 billion years, the majority of the observable universe is within a grabby alien civilization, but large gaps still exist where observers would see no obvious sign of aliens in their observable universes. To your point about multiple 5 billion year old civilizations, this particular sim shows only about 8-10 existing grabby alien civs in the observable universe 5 billion years ago; if evenly distributed, their origin points would be separated by over 5 billion light years on average today, and when randomly distributed there would be smaller and large gaps. "Older civilization far, newer civilization closer" is therefore unsurprising, given how incredibly rare grabby aliens are (only 87 appear in total for this particular simulation over the 20 billion years it takes for the observable universe to be full).

The grabby aliens model doesn't "contrive an answer where they HAVE to be there", it hypothesizes the existence of grabby aliens (defined as civilizations that expand quickly and radically modify stars and galaxies for their use) specifically and explicitly to explain why humans have appeared very early in the universe's history without rejecting the Copernican principle: it proposes that we aren't special, and have in fact appeared close to the end of the time in the universe when we could have possibly spawned before the universe is filled. The model then constrains the appearance rate and expansion speeds of these grabby aliens due to the fact that we don't currently observe them.

Of course, everything here assumes that we are not, in fact, extremely special or unique in the timing or presence of our civilization. That we are not alone, and that we have not appeared early due to luck.

Feels similar to the probabilistic Doomsday Argument, which makes no practical sense.

In this case SOMEONE had to be early. It might as well be us. It doesn’t need invisible grabby aliens to CAUSE our earliness to be normalised.

Just like SOMEONE has to win the Powerball lottery draw. However improbable it might be for any specific individual.

We just won the cosmic lottery. As will many others over the ensuing trillions of years of the universe’s existence. We just happen to be in the first 13.8 billion years.

Offline whitelancer64

Statistical we wouldn't be first or last. There are  trillions of planets out there. Life on earth has existed for few 100million years and we've gone from ape to spacefaring in 100,000years.

My argument here is the same as it has been in the many other similar threads on this topic.

Evolution does not have a purpose or a goal, and it does not necessarily select for complexity or intelligence. Simple / Bacterial life forms ruled the Earth for ~4 billion years. There is no particular reason, that we know of anyway, that they could not have continued to be the dominant life form for tens of billions of years.

There may be trillions of planets out there with such simple life, but that does not guarantee they will eventually produce an intelligent species that creates a civilization. Even using Earth as an example, it is statistically very unlikely. We are the only one of many billions of the complex species on Earth that has developed the high level of intelligence we have.

And even if a species develops intelligence, it may not have the capability or resources to produce technology. A human-intelligent dolphin could never smelt metals and build a radio, for example. Or their planet may not have a crust rich in workable metals, or they don't have any animals suitable for domestication, or crop plants that can be grown en mass with storable seeds for food during lean seasons / years. Humanity really hit the jackpot with a large amount of exploitable resources on our planet.

It's also possible also that supernovae and gamma ray bursts extinguish life in large areas of the galaxy (one of the several possible Great Filters).

Anyway, when I plug in my personal estimates into the Drake equation, I get maybe 5 technological civilizations in our galaxy. I don't think we are alone, but I think it may be a very long time before we find another intelligent, technology-making civilization. It is entirely possible we are the first (at least in our galaxy or in our region of the galaxy) to be able to leave our home planet.
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Offline Yiosie

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

But the reason why the grabbies have to be farther away, is because if they weren't, then they'd likely have already grabbed us by now. The older they are, the grabbier they can be, since their engineering capabilities only grow with time, and their Von Neumann swarms have more time to grow in size and voraciousness (provided their own swarms don't swarm back at them)

Why is it that "the simpler alternative is that they’re just not there in the first place" ?? Why is that simpler?
Simpler that they're not there? Or simpler that they're just not grabby?

That’s a bit like arguing the reason the boogeyman has to be on Easter Island rather in New York is because if he was in New York he would have attacked us by now.

EDIT

If you don’t see any aliens, surely it is simpler to argue they are not there (until evidence proves otherwise), than to contrive an answer where they HAVE to be there, but they all just happen to be at a distance where their age does not allow their light to have reached us yet.

There could be multiple 5 billion year old civilizations, but according to this theory they just happen to all be more than 5 billion light years away. When in reality their distribution should be random, as the Milky Way or Andromeda is just as old as galaxies 5 or 10 billion light years away.

There's a video on YouTube from one of the co-authors of the paper proposing the grabby aliens hypothesis that shows a 3D simulation of a median scenario in their model:



The first grabby alien civilizations only appear about 6 billions years after the Big Bang due to the lack of heavy elements in Population III and II stars formed in the early universe. After 13.8 billion years, the majority of the observable universe is within a grabby alien civilization, but large gaps still exist where observers would see no obvious sign of aliens in their observable universes. To your point about multiple 5 billion year old civilizations, this particular sim shows only about 8-10 existing grabby alien civs in the observable universe 5 billion years ago; if evenly distributed, their origin points would be separated by over 5 billion light years on average today, and when randomly distributed there would be smaller and large gaps. "Older civilization far, newer civilization closer" is therefore unsurprising, given how incredibly rare grabby aliens are (only 87 appear in total for this particular simulation over the 20 billion years it takes for the observable universe to be full).

The grabby aliens model doesn't "contrive an answer where they HAVE to be there", it hypothesizes the existence of grabby aliens (defined as civilizations that expand quickly and radically modify stars and galaxies for their use) specifically and explicitly to explain why humans have appeared very early in the universe's history without rejecting the Copernican principle: it proposes that we aren't special, and have in fact appeared close to the end of the time in the universe when we could have possibly spawned before the universe is filled. The model then constrains the appearance rate and expansion speeds of these grabby aliens due to the fact that we don't currently observe them.

Of course, everything here assumes that we are not, in fact, extremely special or unique in the timing or presence of our civilization. That we are not alone, and that we have not appeared early due to luck.

Feels similar to the probabilistic Doomsday Argument, which makes no practical sense.

In this case SOMEONE had to be early. It might as well be us. It doesn’t need invisible grabby aliens to CAUSE our earliness to be normalised.

Just like SOMEONE has to win the Powerball lottery draw. However improbable it might be for any specific individual.

We just won the cosmic lottery. As will many others over the ensuing trillions of years of the universe’s existence. We just happen to be in the first 13.8 billion years.

I also thought of the Doomsday Argument when first reading about this, and saw that Robin Hanson had previously rejected it comprehensively. So I guess there must be some distinction between it and the grabby aliens hypothesis that I don't understand.

Yes, it is very possible that we are early due to luck (that's my personal stance on the question too). Just wanted to focus the discussion back to the hypothesis that inspired the video in the first post. The authors of the paper thought that "someone has to be early, and it might as well be us" ought to be countered with an explanation rooted in the Copernican principle to consider before leaving it up to dumb luck. Their answer is "we're actually not early; we're in the middle of the distribution of emerging spacefaring civilizations", and grabby aliens is their attempt to take that possibility to a logical conclusion.

In any case it was fun to put aside my own priors and explore this hypothesis here.

Offline M.E.T.

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The issue is not about us physically meeting them. It’s about us SEEING (or rather NOT seeing) evidence of their civilizations  in their home galaxies.

The older they are the more visible an effect these “grabby aliens” should have on their stellar neighbourhood. To explain this lack of detection, the Grabby Alien hypothesis says that those old enough to have visibly changed their stellar environments HAVE to be far enough away that the light of their civilization has not had time to reach us yet.

So a “mega structure / stellar engineering capable” civilization could have arisen 500M years ago in a galaxy 1B light years away, but it is not allowed to have arisen in the next door Andromeda galaxy more than 2.5 million years ago. Or in the Milky Way itself more than ~100K years ago. Else we would see evidence of it.

So the theory requires that the older a civilization is, the farther away from Earth it has to be. That’s a weird, rather Earth-centric condition that has no logical or natural reason for existing, other than to make the theory work.

But the reason why the grabbies have to be farther away, is because if they weren't, then they'd likely have already grabbed us by now. The older they are, the grabbier they can be, since their engineering capabilities only grow with time, and their Von Neumann swarms have more time to grow in size and voraciousness (provided their own swarms don't swarm back at them)

Why is it that "the simpler alternative is that they’re just not there in the first place" ?? Why is that simpler?
Simpler that they're not there? Or simpler that they're just not grabby?

That’s a bit like arguing the reason the boogeyman has to be on Easter Island rather in New York is because if he was in New York he would have attacked us by now.

EDIT

If you don’t see any aliens, surely it is simpler to argue they are not there (until evidence proves otherwise), than to contrive an answer where they HAVE to be there, but they all just happen to be at a distance where their age does not allow their light to have reached us yet.

There could be multiple 5 billion year old civilizations, but according to this theory they just happen to all be more than 5 billion light years away. When in reality their distribution should be random, as the Milky Way or Andromeda is just as old as galaxies 5 or 10 billion light years away.

There's a video on YouTube from one of the co-authors of the paper proposing the grabby aliens hypothesis that shows a 3D simulation of a median scenario in their model:



The first grabby alien civilizations only appear about 6 billions years after the Big Bang due to the lack of heavy elements in Population III and II stars formed in the early universe. After 13.8 billion years, the majority of the observable universe is within a grabby alien civilization, but large gaps still exist where observers would see no obvious sign of aliens in their observable universes. To your point about multiple 5 billion year old civilizations, this particular sim shows only about 8-10 existing grabby alien civs in the observable universe 5 billion years ago; if evenly distributed, their origin points would be separated by over 5 billion light years on average today, and when randomly distributed there would be smaller and large gaps. "Older civilization far, newer civilization closer" is therefore unsurprising, given how incredibly rare grabby aliens are (only 87 appear in total for this particular simulation over the 20 billion years it takes for the observable universe to be full).

The grabby aliens model doesn't "contrive an answer where they HAVE to be there", it hypothesizes the existence of grabby aliens (defined as civilizations that expand quickly and radically modify stars and galaxies for their use) specifically and explicitly to explain why humans have appeared very early in the universe's history without rejecting the Copernican principle: it proposes that we aren't special, and have in fact appeared close to the end of the time in the universe when we could have possibly spawned before the universe is filled. The model then constrains the appearance rate and expansion speeds of these grabby aliens due to the fact that we don't currently observe them.

Of course, everything here assumes that we are not, in fact, extremely special or unique in the timing or presence of our civilization. That we are not alone, and that we have not appeared early due to luck.

Feels similar to the probabilistic Doomsday Argument, which makes no practical sense.

In this case SOMEONE had to be early. It might as well be us. It doesn’t need invisible grabby aliens to CAUSE our earliness to be normalised.

Just like SOMEONE has to win the Powerball lottery draw. However improbable it might be for any specific individual.

We just won the cosmic lottery. As will many others over the ensuing trillions of years of the universe’s existence. We just happen to be in the first 13.8 billion years.

I also thought of the Doomsday Argument when first reading about this, and saw that Robin Hanson had previously rejected it comprehensively. So I guess there must be some distinction between it and the grabby aliens hypothesis that I don't understand.

Yes, it is very possible that we are early due to luck (that's my personal stance on the question too). Just wanted to focus the discussion back to the hypothesis that inspired the video in the first post. The authors of the paper thought that "someone has to be early, and it might as well be us" ought to be countered with an explanation rooted in the Copernican principle to consider before leaving it up to dumb luck. Their answer is "we're actually not early; we're in the middle of the distribution of emerging spacefaring civilizations", and grabby aliens is their attempt to take that possibility to a logical conclusion.

In any case it was fun to put aside my own priors and explore this hypothesis here.

Thanks for the interesting discussion. Much appreciated.

Offline Vahe231991

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Statistical we wouldn't be first or last. There are  trillions of planets out there. Life on earth has existed for few 100million years and we've gone from ape to spacefaring in 100,000years.
Evolution does not have a purpose or a goal, and it does not necessarily select for complexity or intelligence. Simple / Bacterial life forms ruled the Earth for ~4 billion years. There is no particular reason, that we know of anyway, that they could not have continued to be the dominant life form for tens of billions of years.

There may be trillions of planets out there with such simple life, but that does not guarantee they will eventually produce an intelligent species that creates a civilization. Even using Earth as an example, it is statistically very unlikely. We are the only one of many billions of the complex species on Earth that has developed the high level of intelligence we have.

And even if a species develops intelligence, it may not have the capability or resources to produce technology. A human-intelligent dolphin could never smelt metals and build a radio, for example. Or their planet may not have a crust rich in workable metals, or they don't have any animals suitable for domestication, or crop plants that can be grown en mass with storable seeds for food during lean seasons / years. Humanity really hit the jackpot with a large amount of exploitable resources on our planet.

It's also possible also that supernovae and gamma ray bursts extinguish life in large areas of the galaxy (one of the several possible Great Filters).

Anyway, when I plug in my personal estimates into the Drake equation, I get maybe 5 technological civilizations in our galaxy. I don't think we are alone, but I think it may be a very long time before we find another intelligent, technology-making civilization. It is entirely possible we are the first (at least in our galaxy or in our region of the galaxy) to be able to leave our home planet.
Tetrapod species usually exist for a timespan of 4-5 million years, and Homo sapiens will be no exception (a paper by Gregory Paul published in 2008 considers it impossible for species to exist for tens of millions of years).

Your semi-pessimism about intelligent, technologically advanced extraterrestrial civilizations existing in the Milky Way is probably legitimate because, back when my grandparents and parents were born, most people believed that the "canals" on Mars were waterways built by an extraterrestrial civilization, yet the Mariner 4 mission refuted that narrative by demonstrating that the "canals" were mere illusions created by craters and other Martian features previously undetected by the telescopes used by many astronomers in the early 20th century.

Offline daedalus1

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This question is too big, I wouldn't bet against other civilizations in the universe as it is effectively infinite.
The question should refer just to our galaxy.
I would, given all the available evidence bet against another civilizations apart from out own.

 

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