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New Theory of Gravity Might Explain Dark Matter (phys.org)
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.
Slashdot posting an article on fundamental physics? Must be a slow news day.
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 !
Religous speak to God. Insane are spoken to by God. When all shut up, one can finally hear Shostakovich in peace
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.
Government cannot make man richer, but it can make him poorer. - Ludwig von Mises
Oh sure...
It can explain "Dark Matter"; but can it explain other TV series, like "Killjoys", and all the time travel series?
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
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...
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?
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?
We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
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.
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.
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.
"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson
No it is more than just a "thing" - we know that it behaves like matter in many ways thus the name.
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)
That's okay. Gravity believes in you, and it wants a hug.
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?
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes