Emergent Gravity Disproved 102
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)."
Author James P. Hogan used this theory (Score:2)
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That was only a glossover explanation to explain their gravity control. Technobabble with a small root in contemporary science.
Still, great series using medium-hard science and a fun reveal chain. Mod up parent, Inherit the Earth!
Here we go again (Score:5, Informative)
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 [arxiv.org] 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 (Score:5, Funny)
I don't even understand what that title means, but it sounds very cool.
Re:Here we go again (Score:5, Funny)
> 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...
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woosh....
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> I am a gravitational theorist. I don't even understand what that title means, but it sounds very cool.
It means the GP is a self-proclaimed expert at cracking Yo Mama jokes.
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I am a gravitational theorist.
I don't even understand what that title means, but it sounds very cool.
I think what you meant was "it sounds very attractive."
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> I am a gravitational theorist.
I don't even understand what that title means, but it sounds very cool.
It's a regular theorist who lives solely on a gamer diet (cheetos and mountain dew).
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> I am a gravitational theorist.
I don't even understand what that title means, but it sounds very cool.
I'm going to start telling people I'm a gravitational engineer.
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I think it means most of his work revolves around him.
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This is a non-peer-reviewed article ... and the arguments in this article are very very weak.
I wish they would hurry up and peer-review it so it would be correct.
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There's nothing to peer review, because the 'paper' doesn't publish a new theory. All it says is that resulting forces require a statistical 'average' of a couple of forces and that statistical analysis resulst doesn't match with what the entropic force theory calculations predict, but does match with Newton gravity.
That doesn't disprove entropic gravity, but merely sais that the current formula's not correct.
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This is a non-peer-reviewed article ... and the arguments in this article are very very weak.
I wish they would hurry up and peer-review it so it would be correct.
Note that "and" is not the same as "thus".
Paywall (Score:3)
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.
Let me explain this to you... (Score:1)
...in very simple words:
Exciting headlines get page hits.
A statement like "some data gathered might suggest gravity isn't entropic" will get very few page hits, and hence generate very little ad revenue.
A completely wrong but much more interesting statement like "Emergent Gravity Disproved" will get more hits, and hence more money.
So, Kdawson has every incentive to state the title wrongly, whether he understands it or not.
Complain all you want, the nature of the beast does not change.
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I guess you didn't actually read the linked paper.. the paper itself explicitly does claim to disprove the Verlinde theory of emergent gravity
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Kdawson, could you please try to have the first clue about something that you submit?
Those are fighting words, mate! It almost sounds like you're gunning for a newly vacated position [slashdot.org]. In which case you probably should have worked up the courage to post as someone identifiable rather than AC.
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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
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Your willingness to engage in this conversation is appreciated. However, you still have not convinced me that kdawson ought to be criticized for not being a theoretical physicist. From the article his submission cited:
"Experiments on gravitational bound states of neutrons unambiguously disprove the entropic origin of gravitation," he [Kobakhidze] says.
You are well within your rights to express disagreement with such strong language, but why single out kdawson - who seems merely to be a messenger for someone else's words? You should just as well accuse MIT's Technology Review of ignorance and sensationalism since they are the originators
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Okay, one at a time.
I don't have to supply credentials - I merely linked to an article in which someone WITH credentials took this author's work apart. That, at the very least, makes his conclusions doubtful. My credentials really are irrelevant at that point, and I maintain anonymity as my colleagues really do read this.
Well, I guess we'll just have to take you at your word on that wont we? There is no way for us to know if instead of being a theoretician, you're actually just a really well-read waiter who's pissed at being beaten out by Jim Parsons during the casting of "The Big Bang Theory". Don't worry, we'll keep your identity secure from the other waiters. However, you really should forgive kdawson for not tipping you the other night. In all fairness you *did* spill his drink and ruined his pan
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You've got several choices depending on what you are contributing...
If it's something you remember from reading an article, reference the article. That's informative to other readers.
If it's something you have encountered in the past, that's experience and informative too.
As a researcher, you will be expected to maintain a research profile by publishing articles and papers. In your conclusions, you are going to have to express an opinion. It should be unbiased and based on empirical research.
Slashdot artic
Re:Here we go again (Score:4, Interesting)
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 [blogspot.com]
Motl also responds directly to Verlinde here: ;)
http://motls.blogspot.com/2010/01/erik-verlinde-why-gravity-cant-be.html [blogspot.com]
The discussion of a two-slit interference experiment in a gravitational field is clear enough that even I can almost understand it.
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Or fathering another sibling for you...
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This guy sounds pretty convinced and pretty much closes the chapter at the end of the blog entry http://motls.blogspot.com/2011/08/once-more-gravity-is-not-entropic-force.html [blogspot.com]
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I admire the entropic gravity theory, from what little I can understand about it, though I am not sure I buy it.
That said, I am not sure I buy Lubos Motl Pilsen's rebuttal, either. He makes two two points that seem weak to me.
Re:Here we go again (Score:5, Informative)
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.
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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.
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I think gravity ISN'T entropic
Could you elaborate on that? What are your reasons for thinking that? It seems to me that emergent gravity is an obvious conclusion from the holographic principle. I'm not a gravitational theorist and I don't claim to fully understand these things. But as far as I understand it, the holographic principle basically says that a really complicated theory with explicit gravity is exactly equivalent to a much simpler theory without explicit gravity. Given that, it seems obvious to conclude that the simpler
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Its just a theory. I advocate intelligent shoving ;)
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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.
You can determine that by reading it? I can't imagine what complexities are involved, but how long did you spend on the paper, and also are there gravitational, like... experimentalists? You know, guys who take these theories and do experiments?
What would you have bumped (Score:2)
Seriously, I read about this three days ago.
Would you have bumped the departure of Steve Jobs in favor of this story? If not, which story would you have chosen to bump? Think of Slashdot on weekends as a weekly publication that has articles of lower urgency.
Motl comments (Score:5, Informative)
Once more: gravity is not an entropic force [blogspot.com]
Great ! (Score:1)
It's great that something can be disproved in physics these days, it means that physics it's still alive as a science. I hope it's true.
Gravity again? (Score:5, Funny)
I thought that we decided to go with intelligent falling?
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Of course. You know, information is neg-entropy. So if entropic gravity is disproved, then obviously information gravity is proved. Now information comes from intelligence, therefore we have intelligent gravity, i.e. intelligent falling.
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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.
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I don't know what you consider as "making practical sense", but a theory which mathematically works (and GR doesn't work "at times", it works everywhere where we can test it) is considered correct.
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Hi cj,
I think think the idea's got legs.
You can see some of my thoughts on this via the comments by Marble on someone else's blog. [dumbscientist.com]. (You'll have to scroll down / ctrl-f for gravity).
I gave up arguing not because he convinced me otherwise - but lets just say he has a greater belief in the infallibilty of published science that I (or history I believe) can afford to give it.
Cheers, Marble.
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"Gravitational lensing" is a known, 100% solid, FACT. Doesn't matter how much you dislike the idea, world+dog has seen it's effects in action, here on planet earth.
Nice. What keeps the atmosphere (the source of that pressure) grounded, then? Why don't high-altitude (edge-of-space) pilots go floating off? Why d
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The funny thing about science is that you can do experiments to see who's right. You don't have to endlessly debate stuff.
GP states many experimental observations that directly contradict your hypotheses. Now you can whine about condescension, or man up and rethink them.
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You've made a complete and total fool out of yourself by spouting off baseless nonsense that flies in the face of observed facts. Condescension is the best you can possibly hope for.
GRAVITATIONAL LENSING. Doesn't have a damn thing to do with what school you went to. You can grab a telescope and go observe it, in action, RIGHT
Very Valid Theory (Score:1)
Currently it is obvious that physics has been stuck in a rut for decades. The discovery of virtual particles has yet to be fully incorporated into other th
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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".
As far as I know, nobody ever claimed it would.
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And I bet you are not qualified to call even one of the concepts you mention "bunk".
I don't need to be. It is widely know they all the concepts I mentioned are UNPROVEN THEORIES.
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And I bet you are not qualified to call even one of the concepts you mention "bunk".
I don't need to be. It is widely know they all the concepts I mentioned are UNPROVEN THEORIES.
So you think that every unproven theory is bunk? In that case I want to inform you that I don't have a proof of the theory that your IQ is above 70. So I guess that theory, being unproven, is bunk, and therefore I'm safe in assuming that your IQ doesn't exceed 70.
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So you think that every unproven theory is bunk? In that case I want to inform you that I don't have a proof of the theory that your IQ is above 70. So I guess that theory, being unproven, is bunk, and therefore I'm safe in assuming that your IQ doesn't exceed 70.
I think it's obvious who the child is here.
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thank you! short, sweet, and to the point. I have mod points today. Pity I posted to this submission earlier today.
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Vacuum energy is an underlying background energy that exists in space even when the space is devoid of matter (free space). The concept of vacuum energy has been deduced from the concept of virtual particles, which is itself derived from the energy-time uncertainty principle. The effects of vacuum energy can be experimentally observed in various phenomena such as spontaneous emission, the Casimir effect, the van der Waals bonds and the Lamb shift, and are thought to influence the behavior of the Universe on cosmological scales.
The vacuum energy also has important consequences for physical cosmology. Special relativity predicts that energy is equivalent to mass, and therefore, if the vacuum energy is "really there", it should exert a gravitational force. Essentially, a non-zero vacuum energy is expected to contribute to the cosmological constant, which affects the expansion of the universe. In the special case of vacuum energy, general relativity stipulates that the gravitational field is proportional to -3p (where is the mass-energy density, and p is the pressure). Quantum theory of the vacuum further stipulates that the pressure of the zero-state vacuum energy is always negative and equal to . Thus, the total of -3p becomes -2: A negative value. This calculation implies a repulsive gravitational field, giving rise to expansion, if indeed the vacuum ground state has non-zero energy. However, the vacuum energy is mathematically infinite without renormalization, which is based on the assumption that we can only measure energy in a relative sense, which is not true if we can observe it indirectly via the cosmological constant.
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Of course if you want to have real theoretical fun, consider a black hole (important in Entropic gravity theory) no longer as a collection of compressed molecules, but as an oversized atom, where gravity, compression and extreme energy levels has forced a fundamental change in the arrangement of the subatomic particles that make up a black hole. Similarly that neutron stars and pulsars are attempting to behave like a very large transitional state molecule.
It is worthwhile to keep in mind that interaction
Bad headline... (Score:2)
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Interesting.
Thanks for the insight; I also found interesting the point that centrifugal force and inertia are so gravity-like. So my intuition would say that gravity is heavily dependent on motion, maybe not only of macro objects, but also of micro objects (particles and their interactions, which may be why bigger particle conglomerations are more gravitic).
I am still working on this one tho, but I really think that gravity is motion (and by connection, time, which is the emergent property of motion) depend
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If you could point out exactly why you disagree with me then I'd be glad to argue further.
Emergency Gravity (Score:2)
At first pass I read the headline as "Emergency Gravity Disallowed".
My thought was, "Wow, this Hurricane Irene hysteria has really gotten out of hand. People are even afraid the gravity's going to get knocked out."
Obligatory (Score:2)
-You're flying!
-How?
-Gentoo! [xkcd.com]