Author Topic: I don't think we understand the gravity of the situation  (Read 5319 times)

Offline Stormbringer

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Newton and even Einstein may be wrong. And if they are it is probably wonderful. I have read a couple of articles on an up and coming alternative to Einstein's version of gravity over the past few days.

Essentially; Einstein's version does not work and has not worked since the early 20 century astronomers saw galaxies for the first time. Sure you can posit a 900 percent fudge factor and name it dark matter. but the only evidence for dark matter appears to be that Einstein is right so there must be that much unseen matter for the equations to match the observed motions and behaviors of cosmic matter out there. There isn't any dark matter particle detections at ever higher and higher collision energies in ever bigger and more expensive colliders.

So what if there was a theory that explains the observed universe without dark matter?

There is:

https://www.sciencedaily.com/releases/2006/02/060214080204.htm

( ^This article mentions new types of fields? whats that all about, eh?)

http://www.spacedaily.com/reports/Verlindes_new_theory_of_gravity_passes_first_test_999.html


So to over simplify:

both of these theories explain the motions of galaxies but one requires no dark matter fudge factor and the other requires a huge dark matter fudge factor that is adjusted until it explains the observed properties of galaxies.

So anyway what's up with those fields; eh?
« Last Edit: 12/14/2016 02:56 AM by Stormbringer »
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Offline hop

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Re: I don't think we understand the gravity of the situation
« Reply #1 on: 12/14/2016 03:10 AM »
Quote
Essentially; Einstein's version does not work and has not worked since the early 20 century astronomers saw galaxies for the first time.
Err... no. Relativity works just fine. Some people have tried to use modified gravity as an alternative to dark matter, but these theories tend not to be able to account for all the observational evidence.

edit:
Calling dark matter a "fudge factor" is not particularly useful. It's currently the model that gives the best match to a broad range of observations. If you think it's wrong, that's fine, but to replace it you have to come up with a model that does a better job. To date, the alternatives have had a lot of trouble doing that.
« Last Edit: 12/14/2016 03:22 AM by hop »

Offline Stormbringer

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Re: I don't think we understand the gravity of the situation
« Reply #2 on: 12/14/2016 03:24 AM »
Quote
Essentially; Einstein's version does not work and has not worked since the early 20 century astronomers saw galaxies for the first time.
Err... no. Relatively works just fine. Some people have tried to use modified gravity as an alternative to dark matter, but these theories tend not to be able to account for all the observational evidence.
think about it Einstein's relativity predictions for galaxies do not predict accurately what was going on with galaxies until dark matter was posited and adjusted until the equations matched observations. at least according to that article i cited. and the same thing for Newton if the article is to be believed.

Quote
The 'problem' with the golden laws of Newton and Einstein is whilst they work very well on earth, they do not explain the motion of stars in galaxies and the bending of light accurately. In galaxies, stars rotate rapidly about a central point, held in orbit by the gravitational attraction of the matter in the galaxy. However astronomers found that they were moving too quickly to be held by their mutual gravity - so not enough gravity to hold the galaxies together instead stars should be thrown off in all directions!
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Offline hop

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Re: I don't think we understand the gravity of the situation
« Reply #3 on: 12/14/2016 03:43 AM »
think about it Einstein's relativity predictions for galaxies do not predict accurately what was going on with galaxies until dark matter was posited and adjusted until the equations matched observations.
That article is a really garbled oversimplification of the situation.

Galaxy rotation isn't the only observation you need to deal with, you also have to explain things like the bullet cluster and CMB. A "fudge" that turns out to have predictive power outside of the original thing it was supposed to explain isn't much of a fudge.

Again, this isn't to say that LCDM is the final answer, but if you want to replace it you have to actually do the work and come up with something better. People have been trying for a long time, and so far haven't done it convincingly.

Offline meberbs

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Re: I don't think we understand the gravity of the situation
« Reply #4 on: 12/14/2016 04:21 AM »
This was summarized succinctly on xkcd recently: http://xkcd.com/1758/

I have had thoughts before about trying to find alternatives to dark matter, since it really feels like there should be another answer, but a lot have people have spent a lot of time thinking about this, and it really looks like the answer is dark matter.

Offline Stormbringer

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Re: I don't think we understand the gravity of the situation
« Reply #5 on: 12/14/2016 04:32 AM »
the articles mention MOND as one such alternative that is leaving the fringe lately. not true fringe but disreputable or something like that. at any rate the articles claim it is finding new support in the science community.

EDIT:  i don't think the XKCD thing is an accurate summary of it. It's an accurate summary of mainstream science opinion of it. :)
« Last Edit: 12/14/2016 04:35 AM by Stormbringer »
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Offline hop

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Re: I don't think we understand the gravity of the situation
« Reply #6 on: 12/14/2016 05:13 AM »
Astrobite post today covers the paper mentioned in the second link in the OP https://astrobites.org/2016/12/13/emergent-gravity-faces-its-first-test-in-galaxy-lensing/

Offline meberbs

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Re: I don't think we understand the gravity of the situation
« Reply #7 on: 12/14/2016 06:22 AM »
the articles mention MOND as one such alternative that is leaving the fringe lately. not true fringe but disreputable or something like that. at any rate the articles claim it is finding new support in the science community.

EDIT:  i don't think the XKCD thing is an accurate summary of it. It's an accurate summary of mainstream science opinion of it. :)
The mainstream science opinion of people who have spent many, many years trying to find theories that match the data, as opposed to the opinion of people who haven't even looked at all of the data?

When you say that physicists had considered MOND disreputable, you are showing that you don't understand how physics works. MOND is one of (really a category of) the alternatives to dark matter. while it has some attractive properties, no one has been able to make it work, either with matching all experimental data, or forming a consistent full theory from it. This doesn't make it "disreputable," it just makes it not the current best guess at how things work. Physicists can go back and check it again if they get new data that might support or more conclusively refute it.

Offline john smith 19

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Re: I don't think we understand the gravity of the situation
« Reply #8 on: 12/14/2016 10:26 AM »
Anytime I seem some new theory about anything I ask 2 questions.

1) Does it explain all the known observations ?

2) Does it make predictions that can (now or in the future) be tested?

If it can't do 1) it's not as good as what exists and if can't do 2) it's not much use for future work.  :(

Lastly when someone says "The current theory does not explain X" I'd question if that's true or if the person saying that does not understand the explanation the current theory gives.

So how does this idea stack up ?
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Stormbringer

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Re: I don't think we understand the gravity of the situation
« Reply #9 on: 12/14/2016 05:13 PM »
well on that note:  https://www.google.com/search?q=dark+matter+search+comes+up+empty&ie=utf-8&oe=utf-8

more and more powerful experiments keep coming up empty or at least pushing the parameters for dark matter particles "yust one more expensive collider facility build away"

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Offline Robotbeat

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Re: I don't think we understand the gravity of the situation
« Reply #10 on: 12/14/2016 05:36 PM »
This was summarized succinctly on xkcd recently: http://xkcd.com/1758/

I have had thoughts before about trying to find alternatives to dark matter, since it really feels like there should be another answer, but a lot have people have spent a lot of time thinking about this, and it really looks like the answer is dark matter.
Beat me to it.
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Offline Robotbeat

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Re: I don't think we understand the gravity of the situation
« Reply #11 on: 12/14/2016 05:37 PM »
Also, this clearly is a new physics topic.

New physics doesn't mean it isn't real necessarily, it means it's new physics. Not an advanced concept.
« Last Edit: 12/14/2016 05:37 PM by Robotbeat »
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Offline Robotbeat

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Re: I don't think we understand the gravity of the situation
« Reply #12 on: 12/14/2016 05:38 PM »
This was summarized succinctly on xkcd recently: http://xkcd.com/1758/

I have had thoughts before about trying to find alternatives to dark matter, since it really feels like there should be another answer, but a lot have people have spent a lot of time thinking about this, and it really looks like the answer is dark matter.
Dark matter makes sense to me. Dark energy better fits the meme people try to pin on dark matter.
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Offline momerathe

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Re: I don't think we understand the gravity of the situation
« Reply #13 on: 12/15/2016 02:47 PM »
Looks like it's time for someone get their grant funding renewed.

Look, there's value in studying these alternatives. There's value in studying MOND, even though it's almost certainly wrong. But there's no call to go around believing these speculative theories, or treating them as anything more than a toy model - especially not based on a press release.
thermodynamics will get you in the end

Offline Quantum Gravity

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Re: I don't think we understand the gravity of the situation
« Reply #14 on: 06/15/2017 11:35 PM »
 
Sure you can posit a 900 percent fudge factor and name it dark matter. but the only evidence for dark matter appears to be that Einstein is right so there must be that much unseen matter for the equations to match the observed motions and behaviors of cosmic matter out there. There isn't any dark matter particle detections at ever higher and higher collision energies in ever bigger and more expensive colliders.

   
More and more serious mainstream physicists have doubts
about dark matter. It is enough to search in Google.
 
The existence of antimatter was first predicted theoretically,
and later it was also directly detected experimentally,
in addition to being even artificially created.

However, the existence of dark matter has neither been
directly detected experimentally, nor has dark matter been
theoretically predicted in quantum physics
by any mathematical equations.

It is even worse than that.

If the existence of matter is naturally accompanied
by antimatter, then shouldn’t we also expect
the existence of anti dark matter?
     
     
THE MYSTERY OF THE MISSING ANTI DARK MATTER
https://quantumantigravity.wordpress.com/dark-mystery/
     

“ The big mystery about anti dark matter, as far as scientists are concerned, is why there isn’t any of it in the universe. This book is a serious and well-researched exposition of particle physics and cosmology that shows how science came upon anti dark matter and is now trying to understand the asymmetry between dark matter and anti dark matter.  In the first fractions of a second after the Big Bang lingers a question at the heart of our very existence: why does the universe contain so much of dark matter but absolutely no anti dark matter? The laws of physics tell us that equal amounts of dark matter and anti dark matter were produced in the early universe, but then something odd happened. Dark matter won out over anti dark matter. ”

http://press.princeton.edu/titles/8475.html

EXPERIMENTAL Quantum Antigravity — https://quantumantigravity.wordpress.com/

Offline QuantumG

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Re: I don't think we understand the gravity of the situation
« Reply #15 on: 06/15/2017 11:51 PM »
The one thing we know for sure is how little we know.
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Offline Phil Stooke

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Re: I don't think we understand the gravity of the situation
« Reply #16 on: 06/16/2017 12:21 AM »
Shouldn't this thread be in some sort of... I don't know... like astrophysics forum?  This is like posting a cure for cancer on a cooking website.

Offline QuantumG

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Re: I don't think we understand the gravity of the situation
« Reply #17 on: 06/16/2017 01:09 AM »
Shouldn't this thread be in some sort of... I don't know... like astrophysics forum?  This is like posting a cure for cancer on a cooking website.

This section is entirely about these kinds of threads. Now, if only there was some way to ignore an entire section ;)
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?

Offline as58

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Re: I don't think we understand the gravity of the situation
« Reply #18 on: 06/16/2017 06:39 AM »
Shouldn't this thread be in some sort of... I don't know... like astrophysics forum?  This is like posting a cure for cancer on a cooking website.

But what if the cure for cancer is also a delicious dessert?

Anyway, I think this section is very useful for containment purposes. I think it helps to keep some of the stranger things from spilling onto other sections.


Offline Star One

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Re: I don't think we understand the gravity of the situation
« Reply #19 on: 06/16/2017 06:42 AM »
Shouldn't this thread be in some sort of... I don't know... like astrophysics forum?  This is like posting a cure for cancer on a cooking website.

But what if the cure for cancer is also a delicious dessert?

Anyway, I think this section is very useful for containment purposes. I think it helps to keep some of the stranger things from spilling onto other sections.
Good post and fully agree.

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