New Theory of Gravity Might Explain Dark Matter (phys.org) 164
vikingpower writes: Dutch prodigy and Amsterdam University Professor Erik Verlinde published a paper on arXiv yesterday, November 7, titled "Emergent Gravity and the Dark Universe." In the paper, Verlinde derives gravity from the so-called Holographic Principle, which -- simply put -- states that gravity emerges from the interplay between and entropy re-arrangement of sub-atomic "strings" that live in a negatively curved spacetime. At that level [...] spacetime and gravity are emergent from an underlying microscopic description in which they have no a priori meaning." Most importantly, Verlinde's paper has as a consequence that dark matter, nemesis of many an astronomer, is nothing more than an illusion. Verlinde, who was awarded the Dutch national Spinoza science prize in the recent past, already completed the tour de force of deriving Newtonian gravity from the same principles in a 2010 paper, also on arXiv. We are probably looking at Nobel-prize material here, as Verlinde is acknowledged by his peers to "go one better than Einstein's General Theory of Relativity." Slashdot reader turkeydance adds from a report via Forbes (Warning: source may be paywalled): As dark matter continues to vex astronomers, new solutions to the dark matter question are proposed. Most focus on pinning down the form of dark matter, while others propose modifying gravity to account for the effect. But a third proposal is simply to remove gravity from the equation. What if the effects of gravity aren't due to some fundamental force, but are rather an emergent effect due to other fundamental interactions? A new paper proposes just that, and if correct it could also explain the effects of dark matter.
Re:Cue The Usual Suspects (Score:5, Insightful)
how there is no other explanation for the velocity discrepancies than dark matter.
Whoever said that? I've read long ago that people were looking for refinements or new theories of gravity to explain the discrepancy.
"Dark matter" is not even a "thing" - it is a placeholder for something unknown. A simple hypothesis. Could you say it is a bit like the cosmological constant?
Re:Cue The Usual Suspects (Score:4, Informative)
No it is more than just a "thing" - we know that it behaves like matter in many ways thus the name.
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No it is more than just a "thing" - we know that it behaves like matter in many ways thus the name.
And caloric appears to account for the flow of heat--and a depletion of phlogiston is why burning wood results in ashes--and lumnifierous ether is the medium of for the propagation of light waves in interstellar space.
I was always betting that dark matter would turn about to be yet another fictitous fluid with contradictory properties.
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I dont believe in gravity because it's not in the bible
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That's okay. Gravity believes in you, and it wants a hug.
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And caloric appears to account for the flow of heat--and a depletion of phlogiston is why burning wood results in ashes--and lumnifierous ether is the medium of for the propagation of light waves in interstellar space.
So dark matter is the best theory known given the data we have, and if it does get disproved the process of doing so will point us toward better theories? Sounds like science at its best.
But somehow I think you're just looking for a future 'told you so'.
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That seems to be at least as precise as Charles Darwin described evolution, how is that not a theory?
Re:Cue The Usual Suspects (Score:4, Informative)
Except maybe soon we'll know it's not a "thing" after all, if this guy is right. And he seems to have quite a bit of support from colleagues all over the world.
I skimmed the actual paper, probably misunderstood 90% of it, but here's what I think I understood (feel free to correct me, really, I mean it, I would like to know the real story)
- The universe is full of tiny vibrating strings
- Certain particular vibration modes are what we perceive as "particles". Those have less entropy, therefore the presence of mass implies lower local entropy
- Lower entropy somehow causes gravity as some kind of emergent side-effect. Something similar to the theory of elasticity.
- On smallish scales (say, the solar system) the resulting "force" corresponds perfectly to our old formulas for gravity
- On larger scales, entropy of a volume is limited by surface area. Something like the holographic principle, but not quite the same because the entropy is stored all over the volume and not just on its surface. Lots of strings really being the same string due to entanglement? Or something like that.
- This somehow magnifies the effect of gravity for large masses over large distances (say, the scale of a galaxy). Not sure why: maybe the same reduction in entropy has a larger than expected relative effect because of the lower than expected entropy?
- There was also something about large spaces relaxing more slowly, but I lost the plot there. Although it did seem important.
Anyway, if this theory matches observations without introducing new funky constants, dark matter and dark energy could just be totally unnecessary concepts.
(Posting as AC after having modded a whole bunch of off-topic Trump idiots into oblivion)
Re: (Score:3, Interesting)
From your summary, it sounds like the paper attempts to explain galactic rotation curves. Does it have anything to say about gravitational lensing where there's no apparent matter?
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Explain the Bullet Cluster (Score:3)
Sorry, but this doesn't explain actual observations! It may be that some sort of modified gravity is a partial answer, but the mass distribution in galaxy clusters, and possibly other places as well, simply isn't explained by a non-physical effect.
Re: Explain the Bullet Cluster (Score:2)
Re: Explain the Bullet Cluster (Score:1)
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'Density'? 'Flow'? How is this not matter if it is localized in space time and moves around? It sure as fuck smells like matter to me!
WTF turkeydance?!! (Score:2)
Forbes [forbes.com] (Warning: source is anti-adblock and WILL serve ads with MALWARE):
TFTFY.
Also, Forbes, used to be a business magazine. Not really a authoritative source on science an technology.
News for nerds. (Score:5, Funny)
Slashdot posting an article on fundamental physics? Must be a slow news day.
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Only then can we rationally talk about models explaining dark matter.
Melania was talking about dark matter? How nice!
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Disheartening (Score:5, Insightful)
OP here. Obviously, my submission had the bad luck of making it to the Slashdot front page simultaneously with the US presidential elections and their unexpected outcome. Yet I am appalled, truly appalled and disgusted, at what ACs have posted here (see above).
It is now clear to me that after many, many years there is nothing anymore for me on Slashdot. This is it. The level had gone down already for years. The repeated and increasingly vocal racism and vulgarity, the inanity, the name-calling, the bigotry - it had already been putting me off for a long time. Yet I had hoped that, at least for such momentous scientific news as Verlinde's theory, there could have been a discussion worthy of that name.
Slashdot's latest acquirer has done a prolly valiant job to try and turn things around, an effort before which I flourish my hat. It is clear to me, however, that it was too little and too late. I'm leaving slashdot. I will keep reading submissions as an anonymous reader, and that's it. So long, Slashdot !
Re:Disheartening (Score:5, Insightful)
I understand your disgust, but keep in mind that an intelligent person who leaves is contributing as much to the demise of Slashdot as each troll who is added. Either way, the number of good voices compared to the trolls decreases by one.
I hope you reconsider, because this is one of the more interesting articles I've read here in a long time. I just wish I was at a level where I could really grasp its meaning. (As it stands, my depth of physics stops somewhere in the area of general relativity; quantum physics is a bit confusing while string theory is like speaking a different language.)
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The problem is fascist trolls are tolerated here. People discuss with them and let them derail discussions. People have become tolerant of the most outrageous racist and sexist insults. If this tolerance is the prevalent attitude on a forum, no mod system is going to save it.
Re:Disheartening (Score:4, Insightful)
The main problem is allowing anonymous posters. There are good reasons for allowing this, and many ACs like yourself post well thought out comments.
I don't know the solution to this. Perhaps having AC comments start at -1 (or a new -2 score only visible to active mods?)
And then outright banning the hate filled dumbfucks.
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Or just browse at +1 Ac start at zero
Also turn off Ac replies send you notifications. I never see Ac comments to my posts until I go back and read them. By then the mods have shredded them further.
Lastly use the classic slashdot site and say fu to web 2.0 making things difficult
Re: Throwaway accounts as an alternative (Score:1)
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I have used AC commenting in the past because I was also moderating a discussion - then found out I just had to respond to something and me posting non-AC would mean to undo all the modding I already did... dilemma and sometimes a bit vexing when you see 'your' post reaching +5 in the process...
Banning or removing AC functionality doesn't solve any problem unless you make it very hard to register an account or do some very unsavoury things like banning on IP, user profiling using network/browser data and pr
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"I understand your disgust, but keep in mind that an intelligent person who leaves is contributing as much to the demise of Slashdot as each troll who is added."
What is wrong with the demise of Slashdot though? No "intelligent person" should feel any duty to its preservation. Intelligent people should want to be free from garbage and trolling, not obligated to fight them. Tribalism is a fundamental problem, not a fundamental solution.
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I agree. I think what's most important is what ultimately becomes a 'story'. As for the comments it's not too difficult to filter the dross. Any dearth of quality might be expected on a story such as this, where expert knowledge of the subject matter is beyond the ken of even most nerds.
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I don't have anything interesting to add as a comment, but I'm happy that this news made it to the front page. Thanks for submitting it.
Re: (Score:3, Funny)
AC Here, for me your comment is the only one modded high enough for me to see. No idea what happened or what you saw but from my perspective things are working. Now can one of you please post some great analogy so I can understand this.
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It is exactly like having a turtle who discovered he could fly by throwing himself at the ground and missing and discovered he had leg-rockets. Why did he do that? Because he ran out of movies to watch on Netflix and is too large to fit into a VW Beetle, so he was unable to drive to the Library of Congress to try to find something to watch (as he is a typical libertarian he doesn't realize that you can't actually take the movies out of that library). Upon discovering that he became so angry about overreach
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You shouldn't worry about it in this case. The moderation system worked as it should and all those vulgar comments got -1 so they are not visible for most people. I agree that things are far from perfect though. There is much room for improvement.
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I think most people do see the -1 comments. This is the (insignificant) price we pay for wanting to view the whole truth, sort to speak. Otherwise, as repeatedly demonstrated on Slashdot, shills will bury certain painful truths (example: comment on Superfish spyware [slashdot.org]) using downvotes, and some times also coordinate this with a lot of vulgar spamming to force people to hide the low-score comments.
Re:Disheartening (Score:5, Insightful)
I don't think it's that there is more of the crap, it's that there's less of the good.
Trolls and trash have been a part of /. since the early days. I have a low 6 figure UID and I can't remember a time when the GNAA and their ilk were not active here. The difference is that then the quality discussions would be numerous enough to make it appear very different. Once upon a time an article like this might gather a couple of hundred comments, many of them from practicing physicists discussing/criticising/explaining the work. Meanwhile the trolls and shitposters would be downvoted. Anyone reading at 3 and up would probably see some good discussion. Now news like this seems unlikely to get even 100 comments, few are from knowledgable people.
It's like the water-level falling on a river and suddenly you can see all the crap that's been dumped there for years. With so few comments on most articles (there are only 3 articles on my front page with more than 100 comments), you end up reading at a lower level, so you see more of the crap beneath the water.
I wish the new owners of /. well, and I hope they somehow manage to revive it, but I honestly think it's too late, discussion has moved to Reddit or more specialised websites with more active moderation systems. Reddit might be full of trash (including whole subreddits), but the volume is so high, that it's submerged underneath the vast mass and only visible if you choose to go and look for it most of the time.
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I wish the new owners of /. well, and I hope they somehow manage to revive it, but I honestly think it's too late, discussion has moved to Reddit or more specialised websites with more active moderation systems. Reddit might be full of trash (including whole subreddits), but the volume is so high, that it's submerged underneath the vast mass and only visible if you choose to go and look for it most of the time.
It seems to me like the big change is that people don't participate in conversation online like they used to, rather than the conversations and experts moving onto somewhere else. Or at least, if they went somewhere I don't know where it is. It's like using the restroom at a bar and coming back to find the crowd left.
For this specific post, I didn't find any particularly inspiring discussions elsewhere about it. But... this kind of news takes time to process and come up with reasonable comments, and Slashdo
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You mean, GNAA hasn't run you away years ago? It's rare to see an article without an AC shitpost, I don't understand your sudden outrage. Just either don't read at -1 or be prepared to see the noise. The moderation system works.
Re: Disheartening (Score:3)
Good on you for persevering. Glad that I randomly checked in to catch this post. But as a suggestion try r/science on Reddit. The mods there have short tolerance for drivel comments.
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Please keep 'em coming - This started my day off.
I just shared this with my youngest son.
Skepticism (Score:2)
Stick around for a minute and explain how this gravity-modification strategy for getting rid of dark matter doesn't suffer from the exact same problems as MOND.
Your post has a sort of reverse-l'esprit de l'escalier feeling to it, like if you had waited an hour or day you would not have written it. Try not to consider yourself too tightly bound by any vows of pique.
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The level had gone down already for years. The repeated and increasingly vocal racism and vulgarity, the inanity, the name-calling, the bigotry...
Take heart, the Natalie Portman posts are gone.
Vikingpower: Don't Make any Decisions today (Score:2)
I too get sick of endless troll wars but can quickly sift through it.
Thanks vikingpower for the submit to the interesting paper.
As this kind of science is above my job description does this theoretical treatment amend itself to testable confirmation?
Re: Disheartening (Score:1)
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Yet I am appalled, truly appalled and disgusted, at what ACs have posted here (see above).
You must not have your filters set up properly because I don't (have to) see any of it.
Is this string theory again? (Score:2)
Jokes apart, it seems to me like you can derive from it everything you whish, just by messing opportunely with the hypothesis.
Re: (Score:2, Interesting)
No. This is something different altogether. String theory never got as far as explaining even simple classical mechanics aspects. While there are a few hearty souls still plodding on, there is believed to be no real future for string theory.
;-)
Hey, if your theory is based on the sum of all integers being 1/12, you have a common sense problem...
If dark matter is real, entanglement is false (Score:1)
So flipping the paper over, if dark matter is real, quantum entanglement isn't.
So the experimental proof would be to go find the missing matter and disprove entanglement!
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Space can be elastic (Score:4, Informative)
It's strange that Verlinde uses 'elastic' in the abstract.
"The emergent laws of gravity contain an additional dark gravitational
force describing the elastic response due to the entropy displacement."
I think space can be thought of like some kind of elastic material. At first, space begins to regain its original form (where there is no matter) quickly from the center of gravitation. However, as we go further and further from the center this process slows down.
The end result is that space will be more curved than we expect at large distances.
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Oh sure... (Score:5, Funny)
Oh sure...
It can explain "Dark Matter"; but can it explain other TV series, like "Killjoys", and all the time travel series?
Anti gravity? (Score:3, Interesting)
I must confess I'm completely out of my depth here (and not for the first time), but considering that gravity is now considered a dynamic process, would this open the way for anti-gravity devices?
If so within a week we went from nothing to a completely plausible sci-fi universe.. Reactionless drives, anti-gravity... FUN
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The answer to which - as in all unproven things - is "We just don't know".
It's unlikely, as gaps for anti-gravity devices don't exist in any of our mathematics currently, but until you prove what gravity is, guessing at whether anti-gravity is possible is basically moot.
It's like asking if there might be an anti-ghost.
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One thing to bear in mind is that, like any good theory that aims to supplant an existing well-working theory, Verlinde's theory basically matches Relativity 1 for 1 until you get to the galactic scale.
This is just like the way Relativity matches Newtonian Gravity 1 for 1 until you start to get to the inter-planetary scale, after which Relativistic affects can be easily observed.
Noticing the differences between the theory of Relativity and Verlinde's theory at the inter-planetary scale should take precise e
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Well then (Score:2)
It seems it's turtles all the way down. I could follow this gravity saga up to general relativity where it becomes slightly blurred.
Even though I'm excited about new developments in physics, I'm kind of sad it's getting more and more incomprehensible. I just can't grasp strings & holograms at any level. The same goes for modern developments in mathematics.
gravity is not fundamental (Score:1)
Gravity in general relativity is not a fundamental force. It is an apparent force you experience because you chose an inappropriate frame of reference (e. g. you're not free-falling). Much like rotational forces.
I had thought of something similar (Score:3)
I know what you're thinking, "Yeah, sure you did." In this one particular case, I did.
Somewhere in my notes for something I'm working on I posed the question, "Why is it that gravity is a force unto itself? Why can't gravity be the result of the interaction of the other forces?"
I raised that question because no one had detected a gravity wave. Until this year (Feb 11, 2016). So now the question becomes, if gravity waves were detected, how does this discovery affect this paper? Wouldn't that "disprove" the idea and lead to gravity being the force we always thought it was?
Re:I had thought of something similar (Score:4, Insightful)
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I've been saying gravity isn't a thing ever since I saw the first explanation of gravity using a bowling ball on a bed or trampoline. It still isn't proven, but I go about my life as if it is.
Gravity does affect things, and those effects ripple out, and sometimes cause gravitational waves. The only difference is that they aren't caused by gravity as a force.
I think of gravity more like centrifugal force. It's there and measurable, but it isn't real. It's centripedal force, in a different reference frame. Th
I thought the holographic principle was disproven. (Score:2)
Modeling error versus exotic matter (Score:5, Interesting)
Most importantly, Verlinde's paper has as a consequence that dark matter, nemesis of many an astronomer, is nothing more than an illusion.
This has been something I've been asking about for years with no good answer. Namely, what evidence exists to prove that so-called "dark matter" is actually matter rather than a defect in our mathematical model of gravity? Why is this not similar to how Einstein found a better model (relativity) for the phenomena first described by Newton? We're going through all sorts of contortions to try to prove that some mysterious "matter" must be there even though we have no idea what it could possibly be, have no direct observations, and our only evidence for it is inferred from our current models of gravity which we know to be incomplete since they do not work with quantum mechanics. While it certainly might be some form of exotic matter it seems at least equally probable that the answer might instead be that a better model is needed and that our current model is deficient in some way.
One wrong model (Score:2)
I remember MOND theory was debunked as dark matter was proven to be a kind of matter and not an error in Gratitation theory.
Just because MOND isn't the right answer it doesn't follow that the problem cannot be with the model. All that proves is that one specific model doesn't work. And the problems with MOND don't appear to be so much related to dark matter but rather to an inability to predict behavior of galaxy clusters that we can observe. We have direct evidence or workable model for what dark matter is even if we make the (reasonable) assumption that it is indeed some form of matter. It MIGHT be matter but nobody seems
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The reason it's called Dark Matter is because of gravity. Matter is the only thing we know to have gravity, so if there's extra gravity there is (probably) extra matter. Relativity works so perfectly for everything else that the odds of the theory being the problem are very low.
Still, that doesn't mean "Dark Matter" actually matter, it's just a placeholder for this unknown mass of gravity that surrounds every galaxy in the universe. Matter is simply the most likely explanation, so that's what they called it
Re: (Score:3, Interesting)
This has been something I've been asking about for years with no good answer. Namely, what evidence exists to prove that so-called "dark matter" is actually matter rather than a defect in our mathematical model of gravity?
It's like this. There are various evidence of something going on, such as galactic rotations, CMB patterns, gravitational lensing, etc. (These are described in the Wikipedia article on Dark Matter.) There have been, and currently still are, various explanations for these different evidences. Typically, we can do something like give each one a grade like the typical US grading scale of A-F. So far, the idea that there is matter out there that only interacts via gravity scores pretty highly A-C in all these.
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It's called "Dark Matter" because its behaviour is identical to that of matter that doesn't interact electromagnetically; specifically 'cold' (low velocity) matter. It clumps like matter, it has a gravitational field that bends light like matter, and it seems to move like matter. It might very well NOT be matter, because the scientific method is all about being wrong; but so far Lambda-CDM is the best-fit theory.
Neutrino wind (Score:3)
My money is still on gravity being the result of particle wind (maybe neutrinos, maybe some other such). A body resting in isolation is bombarded in all directions and suffers "no gravitational attraction". Place a massive body near by, which blocks the wind in one direction and you see "gravitational attraction" in that direction. Several physicists have tried this angle and made progress but ultimately failed to make it work. However, it still seems the most economical and logically consistent explanation.
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But doesn't really explain why a large obstruction that has little mass would less of an effect than a tiny obstruction with huge mass (e.g. singularities, ultra-dense stars, etc.).
Are you saying that the density of the object doesn't matter? Or are you saying that a large object somehow "sucks in" the wind in areas surrounding it but not directly touching? Which is basically taking you back to curvature of space-time again, albeit with a complication layer in between.
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If you have a particle like the neutrino, which mostly goes through matter, then mass is the most important thing. The more massive you are (dense or not dense) the likelier you are to have an interaction with the wind particle and thus stop the particle from reaching the other body.
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It is a particle wind. The interaction is not with the surface like a sail on a boat, but with individual atoms, like in an X-ray picture.
Boat analogy: you are thinking of a sail made of canvas. A better analogy would be using a fishing net as a sail. Surface area is no longer that important, but rather the total number of knots that were hoisted.
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But then it's also assuming an omnidirectional, fairly constant stream of particles which, when obstructed, has a cone of effect in its outer direction. The "shadow" if you will.
Your hypothesis, with an omnidirectional field, would mean that - at a certain distance from the object casting the shadow - there would be enough affect at virtually-the-same-angles from all the other parts of the wind to make any distance gravity effect infinitesimally small in comparison.
But gravity is constant with distance.
To
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It doesn't work that way. The gravity effect doesn't become infinitesimally small, it actually drops with the inverse square of the distance which is just what the physics predict.
But gravity is constant with distance.
Proportional to the inverse square you mean?
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Feynman talks about this model in his book "six easy pieces" [amazon.fr] and says that this would not work because Galilean motion would be slowed down by this wind, which is not what we are observing.
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There are indeed some issues that need to be worked out, but this one in particular is taken care if we assume that the wind travels at the speed of light, i.e. if composed of photon-like particles.
Hoax (Score:1)
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I usually see things differently (Score:2)
Ether and Dark Matter (Score:2)
When physics couldn't explain what existed beyond earth they invented ether. When physics couldn't explain the expansion of the universe they invented dark-matter.
Same idea and will probably be proved equally laughable one day once we have a better understanding of the universe; but that's science, you come up with a theory until you gain a better understanding and build upon it.
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The idea behind the luminiferous aether was that, if light was a wave, it had to be a wave in something. It wasn't a particularly good explanation even back then, since it hypothesized an ultra-rigid material that suffused all space and had no effect on the motion of planets. As far as I can tell, it existed only to explain light being a wave.
Dark matter, on the other hand, explains several things reasonably well. It started as a way to explain galactic rotation curves, but we also see gravitational l
Gravity might be entropic? (Score:1)
Newtonian is wrong though, so if he derived... (Score:1)
Isn't Newtonian gravity wrong though? It failed to predict the precession of the orbit of Mercury. Correct me if I'm wrong but isn't it just basically the inverse square law, which applies to radiant phenomena (like the intensity of light radiating from a point source.)
So, if this guy 'derived Newtonian Gravity' from his theory, then his theory is wrong too, isn't it?
What am I missing here?
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Deriving Newton's version of gravity is a good sanity check since the conditions for it are easier to work with mathematically (low energy, flat space, etc.). You can do the same thing in General Relativity to show that it actually does describe our universe.
Dark Matter Hides Gravity's Troubled Youth? (Score:1)