Emergent Gravity Disproved

kdawson writes "A paper up on the ArXiv claims to disprove the gravity-from-entropy theory of Erik Verlinde, which we discussed soon after he introduced the idea in a symposium late in 2009. Archil Kobakhidze says that experiments measuring the effect of gravity on quantum particles (neutrons in this case) match results expected from classical Newtonian gravity, not Verlindian entropic gravity. Here is Kobakhidze's paper (PDF)."

Comments

Author James P. Hogan used this theory

[MadMike32]

In his Giant Star novels, if I recall correctly. The great breakthrough in physics by the aliens was the understanding that gravity was a consequence of particles decaying rather than through the standard Einstein model. Kind of puts a torpedo through that aspect of the books.

Here we go again

[Anonymous Coward]

Kdawson, could you please try to have the first clue about something that you submit? This is a non-peer-reviewed article, fresh on the arXiv. It's a followup to an earlier article which was widely criticized within the community as being full of holes, and the arguments in this article are very very weak. At best it's an argument against entropic gravity, but it is a LONG way from a proof that entropic gravity is wrong.

The way that neutron states are treated here is questionable - see http://arxiv.org/abs/1104.4650 for a summary of what's wrong with them.

Disclaimer: I am a gravitational theorist. I think gravity ISN'T entropic. However this paper is nowhere near sufficient to show that. I'd wait a LOT longer for the dust to settle on this one before making a strong statement one way or the other.

Re:Here we go again

[Zedrick]

> I am a gravitational theorist.

I don't even understand what that title means, but it sounds very cool.

Re:Here we go again

[patlabor]

> I am a gravitational theorist.

I don't even understand what that title means, but it sounds very cool.

He attracts a lot of ideas...

Re:Here we go again

[Freddybear]

For more discussion of Kobakhidze's paper, and for criticism of the paper by Chaichian cited above, go here:
http://motls.blogspot.com/2011/08/once-more-gravity-is-not-entropic-force.html

Motl also responds directly to Verlinde here:
http://motls.blogspot.com/2010/01/erik-verlinde-why-gravity-cant-be.html
The discussion of a two-slit interference experiment in a gravitational field is clear enough that even I can almost understand it. ;)

Re:Here we go again

[tloh]

That is a poor excuse for choosing to express yourself as a rude condescending jerk. kdawson may not have the subject matter expertise to evaluate the strength/merit of what he felt was something cool and worth sharing - news for nerds. But how is it you choose to ignore timothy's role as a gate keeper for what is worthy of slashdot? Your own disclaimer express an opinion that the dust has yet to settle - even among experts. Yet you pull no punches in expressing your own opinion and expect us to take it at face value. That isn't the actions of someone fearful of future funding. It is the mark of someone too arrogant to acknowledge progress in science as necessitated by a series of meaningful arguments and counter-arguments within a framework of mutual understanding. What understanding did you attempt to foster here? I'm afraid you have a very skewed understanding of the slashdot community if you expect the link you posted to really mean anything for the majority of readers here. Take a good look at the replies to your post - half of them are cracking jokes and the other half are decidedly not impressed about the nature of scholarly publication. When your done feeling smug and self-important it would be helpful to consider how to undo the damage your post did by obfuscating the subject. An expert is useless if (s)he is incapable of communicating that expertise.

Re:Here we go again

[bcrowell]

Kdawson, could you please try to have the first clue about something that you submit?

There's no reason to be so rude. In fact, I would consider the summary pretty accurate, although maybe not the title.

This is a non-peer-reviewed article, fresh on the arXiv.

Totally irrelevant. New research typically appears on arxiv first. That doesn't mean it's wrong.

It's a followup to an earlier article which was widely criticized within the community as being full of holes, and the arguments in this article are very very weak.

I'm not a specialist in this field (my specialty is experimental nuclear physics), but the impression I get as an outsider is that this is inaccurate. Actually many people in the field seem to find Kobakhidze's arguments very strong. I think the most fair summary would be that right now, the whole thing is controversial. Verlinde never claimed that he had a worked-out theory. It's always just been a rough heuristic. Even if it's right, it's wrong. What I mean by that is that it's at best a provisional picture (historically analogous to the Bohr atom) which needs to be reworked into a real theory (analogous to quantum mechanics). Just as there were no clear criteria for judging whether the Bohr model was a good idea or a dead end in 1915, there are no clear criteria for judging whether this idea is good or a dead end in 2011.

Re:Here we go again

[JamesP]

From the bottom of my heart, a huge thank you

This is the way science should go. Not "disproving theories" with barely acceptable arguments just because it's against the current theory.

Oh, btw (not for you), Einstein's General Relativity is not a theory OF gravity, it's a theory of how things behave in a gravitational field, it doesn't matter if it's a field, particles, entropy or bunnies causing gravity.

Paywall

[tepples]

This is a non-peer-reviewed article

I was under the impression that a peer-reviewed article was more likely to be paywalled and thus inaccessible to those Slashdot readers who had already graduated.

Motl comments

[Sara Chan]

Lubo Motl has some additional, supportive, thoughts on his blog:
Once more: gravity is not an entropic force

Gravity again?

[The Creator]

I thought that we decided to go with intelligent falling?

Re:common sense...

[MightyMartian]

Translation: I'm a fucking moron who doesn't understand things, but loves to insist my ignorance is in fact someone else's problem, so I have no problem spouting pure idiotic bullshit, and through a combination of low IQ and high hubris factor, throw my retarded thoughts out there as if they weren't the mumblings of a halfwit.

Re:Very Valid Theory

[maxwell demon]

Considering the bunk and completely unproved concepts that physics is using currently ie. Dark Matter, Dark Energy, String Theory, Supersymmetry and the Higgs Boson.

You are mixing together very different things here. For one, I don't think anyone is using string theory. And I bet you are not qualified to call even one of the concepts you mention "bunk".

Even IF there is a Higgs particle, the Higgs does NOT explain gravity.

As far as I know, nobody ever claimed it would.