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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)."
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.
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.
Seriously, I read about this three days ago. If you're going to post stuff from the Technology Review arXiv blog, the least you could do is stay current.
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.
...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.
Lubo Motl has some additional, supportive, thoughts on his blog:
Once more: gravity is not an entropic force
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.
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.
We learn from history that we learn nothing from history - Tom Veneziano
I thought that we decided to go with intelligent falling?
FRA: STFU GTFO
Surely thou jest. Everyone knows it was the Flying Spaghetti Monster (FSM) that brought about the existence of the universe. Your god is nothing but an accidental creation that was a result of FSM allowing its snot to achieve self awareness during the binge drinking that following creation.
http://xkcd.com/865/
I'm not a physicist nor do I know how to do the equations that they use. However, I've never understood the bent spacetime model as it makes little practical sense, though it may mathematically work at times.
I'm of the contention that gravity is not a force at all. I believe that the following makes more sense. I believe there is a combination of electromagnetic forces combined with atmospheric pressure that keeps us grounded. Fluid dynamics seems to be where that math might exist.
I'd be interested to hear what others, who do understand some of the math, would think of that proposal, keeping in mind that there seems to be a number of theories that have fallen short recently. One in particular is the speed of light constant being shown to not be limited by such a constant, another 'capped' belief that made little practical sense proven to be incomplete.
l8r,
cj
Considering the bunk and completely unproved concepts that physics is using currently ie. Dark Matter, Dark Energy, String Theory, Supersymmetry and the Higgs Boson. Even IF there is a Higgs particle, the Higgs does NOT explain gravity. Emergent Gravity is a VERY compelling concept. It could also explains Mass, Inertia AND the 2nd law of thermodynamics.
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 theoretical aspects of physics. It is my understanding, that these virtual particles are the 'Ether' that Einstein had mentioned before he resorted to the cosmological constant.
In my opinion, these chaotic particles have an effect,Entropy. Areas with less virtual particles, like the occlusion between two near objects, experience a negative pressure, which we call gravity. Gravity is emergent from Entropy. Entropy is emergent from Virtual Particles.
Of course, this is pure conjecture. But I would love to hear other peoples opinions...
To be fair, the article only addresses one formulation of emergent gravity from a single hypothesis. To say the whole idea of emergent gravity is wrong is a little disingenuous. My pet theory (hey, a boy needs a hobby) is that gravity is emergent from a universe where the physics, the actual computation, has to be done to make anything happen. Apple falls to the ground? The universe has to perform the calculations to make it happen. If there's a processor limit then it would manifest as the speed of light, and if the calculations involving regions of space with mass ("particles") take a little more calculating then that section of space will be retarded in a timelike direction, ie GR. There's a whole host of emergent gravity or emergent relativity possibilities, and to my mind at least it's a very elegant way to get around some of the big fundamental problems, like why gravity doesn't seem to behave like the other forces, or why the speed of light even exists.
Please consider this account deleted, I just can't be bothered with the spam anymore.
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."
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
-You're flying!
-How?
-Gentoo!
Escher was the first MC and Giger invented the HR department.
... it's a *disclosure*. There are things called dictionaries that you should perhaps consult sometime ...
www.thomaswlynch.com/blog at the bottom. Postulates gravity follows from an expanding Klein bottle like geometry for the universe. Note the nifty animation graphic ;-)