The End Of Gravity As a Fundamental Force 650
An anonymous reader writes "At a symposium at the Dutch Spinoza-instituut on 8 December, 2009, string theorist Erik Verlinde introduced a theory that derives Newton's classical mechanics. In his theory, gravity exists because of a difference in concentration of information in the empty space between two masses and its surroundings. He does not consider gravity as fundamental, but as an emergent phenomenon that arises from a deeper microscopic reality. A relativistic extension of his argument leads directly to Einstein's equations." Here are two blog entries discussing Verlinde's proposal in somewhat more accessible terms.
Update: 01/12 04:48 GMT by KD : Dr. Verlinde has put up a blog post explaining in simpler terms the logic of the gravity from entropy paper. He introduces it with: "Because the logic of the paper is being misrepresented in some reports, I add here some clarifications."
Update: 01/12 04:48 GMT by KD : Dr. Verlinde has put up a blog post explaining in simpler terms the logic of the gravity from entropy paper. He introduces it with: "Because the logic of the paper is being misrepresented in some reports, I add here some clarifications."
way cool (Score:5, Interesting)
FTA:"Starting from first principles, using only space independent concepts like
energy, entropy and temperature, it is shown that Newtons laws appear naturally and
practically unavoidably. Gravity is explained as an entropic force caused by a change
in the amount of information associated with the positions of bodies of matter. "
and "... the holographic hypothesis provides
a natural mechanism for gravity to emerge. It allows direct contact interactions
between degrees of freedom associated with one material body and another, since all
bodies inside a volume can be mapped on the same holographic screen."
If this is proven correct - that gravity and inertia are emergent from information entropy
and statistics, it would be very, very exciting if for no other reason than it would be yet
another support (probably the strongest yet) for the holographic universe description /
the 'reduced dimensionality' description. This could also resolve some of the impossibly
inconsistent problems in physics integrating gravity with microscopic forces and spooky
effects like action at a distance.
So far all we've had to support a holographic universe is black hole physics and string
theory conjectures.
It's mind warping to imagine that the whole of our existence necessarily depends
on encodings that are 2-dimensional in nature. If this is the case, what a world
it would be. Philosophers and religious folk will argue over what that might mean.
Re:Just because the math works doesn't mean it's t (Score:4, Interesting)
Well, it does make a jump from a fundamental force we can't seem to detect into a latent, emergent phenomenon which we, er, also can't detect the source of.
So it transfers one critical unknown into a less important, impossible to verify unknown. Then it links up with Relativity somehow. Not exactly a "theory of everything".
Not at an all an expert but... (Score:4, Interesting)
From http://www.scientificblogging.com/hammock_physicist/holographic_hot_horizons [scientificblogging.com] the first of the two blog entries:
The value for G comes out correctly if you enter for Abit the value corresponding to a Planck area. However, the Planck area (G/c3) is defined in terms of Newton's gravitational constant G. Have we not introduced a circular reasoning here? I am actually not sure.
This does seem like an issue. However, it looks like you can do this with G as a variable. The upshot then is not that you get the right value for G at the end but that you get Newton's inverse square law (up to a scalar) which by itself would be really impressive even if one can't a priori get the value of G.
Obligatory disclaimer: I'm a math grad student not a physicist so I could be completely wrong here.
Descriptive analysis of "here is two" (Score:3, Interesting)
But 'here is two', um, seriously? English is my third language and I've yet to have problems with using is for singular and are for plural.
The traditional analysis supporting "here are two" treats the sentence as having been inverted into verb-subject order, an unusual order for English. Dialects admitting "here is two", on the other hand, treat "here" as a singular subject referring to "the set presented here", in the same sense that "everyone" is singular, and "two" becomes the complement.
Comment removed (Score:3, Interesting)
What is "information"? (In that context.) (Score:1, Interesting)
In his theory, gravity exists because of a difference in concentration of information in the empty space between two masses and its surroundings.
One of those words is not like the others. The word “information” does not fit in there. I can’t put it into words, but I can show you what I mean:
Bad:
In his theory, gravity exists because of a difference in concentration of thetans in the empty space between two masses and its surroundings.
In his theory, gravity exists because of a difference in concentration of hope in the empty space between two masses and its surroundings.
In his theory, gravity exists because of a difference in concentration of imagination in the empty space between two masses and its surroundings.
Good:
In his theory, gravity exists because of a difference in concentration of gluons in the empty space between two masses and its surroundings.
In his theory, gravity exists because of a difference in concentration of $particleToBeFoundByLHC in the empty space between two masses and its surroundings.
In his theory, gravity exists because of a difference in concentration of neutrinos in the empty space between two masses and its surroundings.
(Not saying that’s right. Just saying this would be an argument that one could build something around. As opposed to the bad examples.)
Re:Testable, currently unseen predictions. (Score:2, Interesting)
Clearly, the author is aware that a good theory is testable, as that paragraph admits that it's not at that stage right now. That doesn't mean it's meaningless, as most any idea starts out pretty vague.
Re:Just because the math works doesn't mean it's t (Score:5, Interesting)
I do like the idea of not needing an explanatory tool like "Dark Energy" ... that has always bothered me. Far more than "Dark Matter".
Re:Just because the math works doesn't mean it's t (Score:4, Interesting)
Even the simple things that you take for granted, such as Inertia, is not understood. Nobody can explain why there is Inertia, or what mechanisms makes it a requirement.
What is important is that we can model things. If two such models fit observations, then there is no reason to dismiss one of them (such as string theory) out of hand. In the end, neither model is truth. Model's can't explain "why."
Re:Just because the math works doesn't mean it's t (Score:5, Interesting)
That's one funny thing about math, "close doesn't count", until you get to a certain advanced point.
I didn't realize irrational numbers, a huge portion of the rational numbers, and trigonometry, were considered advanced.
But this really isn't about the *math* being close, but not exact, it's about the math being close to *reality*, but not exact. Again, however, this is not advanced. Even grade school science is close but not exact. What's the temperature outside? How many inches of water did it rain last night? What's the circumference of the Earth? And Newtonian physics (which is also not advanced) is close, but not exact. Even at the slow speeds and low gravities of our mundane lives. Special and General Relativity have the honor *not* of being exact, but merely of being closer to exact than anything else so far.
The only common types of math where "close doesn't count" are basic arithmetic (excepting fractions) and pure algebraic manipulation.
In your high school physics class, do you *really* think you were exact when you used 186,000 mi/s or 300,000 km/s for the speed of light? Or in grade school, that the Earth rotates in exactly 24 hours (as measured from solar zenith to solar zenith)?
Or even before that, when you bought one candy bar at 3 for a dollar, and you got 66 cents in change?
Precision and accuracy are two terms you should have been made aware of by high school science, and rounding errors by middle school math.
Re:What is "information"? (In that context.) (Score:5, Interesting)
Dude! Information is a perfectly useful theoretical property in theoretical physics, directly related to entropy. Observe, for instance, all the cool stuff Stephen Hawking has done is related to black hole entropy in some manner or another. (Black holes have to have entropy, otherwise you could violate the second law of thermodynamics by tossing stuff into them.... but if they have entropy, they should emit radiation.... hey, guys, look, a way for black holes to emit radiation and evaporate!!)
As Jacob Bekenstein put it, the trend in physics is to "regard the physical world as made of information, with energy and matter as incidentals." (Bekenstein came up with the Bekenstein bound, a fundamental limit on the amount of information/entropy which can be contained within a space. If you could come up with a system with more entropy in a given space, then you might be able to violate the Second Law of Thermodynamics by tossing it into a black hole.)
In his theory, gravity exists because of a difference in concentration of information in the empty space between two masses and its surroundings.
In his theory, gravity exists because of a difference in concentration of entropy in the empty space between two masses and its surroundings.
Same darned thing.
Re:way cool (Score:5, Interesting)
what does this potentially bring us
The paper posits that gravity is an entropic force, not a fundamental one. He does this by starting with the assumption of a reduced dimensionality universe with one emergent direction for space and shows that as a mass approaches the holographic boundary he can combine statistical mechanics equations and Einsteins equations for mass & energy (throw in a couple hand waves about average energy and degrees of freedom) and he derives Newton's laws and more.
This is fundamentally a different view of how gravity, inertia and space arise compared to the current "fundamental forces" understanding in physics. An accurate and testable understanding of gravity could potentially lead to areas impossible to predict: anti-gravity, energy production, warping and changing space, usable action at a distance for communication or transportation.
This is analogous to the shift in understanding when humans understood and then used the electrical force. Who could have dreamed before electric power of mobile phones, global Internet connectivity, HDTV, Twitter, Superbowl broadcasts, images from Mars, superconducting MRI coils, particle accelerators, etc. etc. A functional understanding of gravity could be even more revolutionary than the change in the human condition from understanding electricity.
Re:Just because the math works doesn't mean it's t (Score:2, Interesting)
Re:Stop posting articles from arXiv! (Score:4, Interesting)
If you've spent any time in academia, you'd know that peer review is a cruel joke.
It's more politics than science.
Somebody didn't get tenure.
I didn't get tenure either, and there were serious political issues, the first time. But that's not a problem with peer review (which I still am asked to do, occasionally). Most PhD's never get tenure, at least not in a research university. Academia is one bitch of a career path.
I still publish papers, in less-prestigious journals and conferences, mostly peer-reviewed. Some papers are turned down. So it goes...
Re:If the math works, then it approximates reality (Score:4, Interesting)
It looks like I have access, so I'll summarize the article. This is the May 2004 "Reference Frame" column in Physics Today, written by David Mermin, titled "Could Feynman Have Said This?"
Mermin came across something that ascribed "shut up and calculate" to Feynman, and was somewhat disturbed. Mermin had written in Physics Today (April 1989) that "If I were forced to sum up in one sentence what the Copenhagen interpretation says to me, it would be "Shut up and calculate!" Therefore he was worried that he perhaps had absorbed the quotation from Feynman at some point, and then used it in his article without proper attribution.
So he embarked on a Google search, finding lots of hits having the quotation as Feynman's, and none for Mermin. But then he realized that none of the web material cited any sources or told the "story" of the quotation. So he thinks he may be a victim of the "Matthew effect," from the "tendency always to assign exclusive scientific credit to the most eminent among all the plausible candidates." In other words, somehow the quotation got attached to Feynman, who is well known for his work in QM.
Next Mermin examines whether or not the witticism actually matches Feynman's personality. He concludes that it doesn't; however Feynman's "habitual irreverence" is probably a factor.
In closing, Mermin lays claim to the saying and awaits evidence that Feynman actually said it.
Re:Stop posting articles from arXiv! (Score:3, Interesting)
Of course this doesn't mean that if you write total crap you'll get published: but that for two identical valuable contributions, politics may favor one with respect to another.
ONLY in a specific publication. That doesn't mean that the contribution can't get published, it just might not be in Nature. So publish the research elsewhere. If the science is good ultimately it doesn't matter where it is published. Journals often will reject articles because they are judged to not be of wide enough interest for the readership of the journal. Has nothing to do with the quality of the science but it's a perfectly valid reason to choose one article over another.
Re:Just because the math works doesn't mean it's t (Score:5, Interesting)
While I agree with your basic premise, let's examine your statement with regards to the number PI.
We have a whole bunch of different equations that calculate what PI is to billions of digits of accuracy.
Is our model of PI more accurate than our measurement of a circle in reality?
Does this mean our model of PI can not be more accurate than our measurements?
Or is there some other way to 'prove' that our model of PI is exact regardless of what our universe measures it as?
--jeffk++
Re:Just because the math works doesn't mean it's t (Score:3, Interesting)
In principle a model could comply with an objective reality with 100% convergence, but we would be forever unable to prove it 100% because there is no direct access to objective reality's fundamentals, only experimentation & prediction. That doesn't mean the model isn't 100% accurate, it just means we can't say (with 100% confidence) that it is.
Re:Stop posting articles from arXiv! (Score:3, Interesting)
Let me echo this sentiment. I did my PhD in a esoteric corner of Number Theory. In my first position after graduate school, I submitted a number of papers. Waited a minimum of one year for rejections or impossible demands for revision. The handful of others in my area refused to collaborate with me. I left academia.
Seven years later, a student of one of these people who refused to collaborate submits a paper,
and somehow I get to be referee. I turned it around reasonably quick, rejected because it overlooked many earlier works.
Later that year, I get a request from the student about the same paper, maybe revised, I didn't look too closely. (He doesn't know I was referee for the previous time around.) It has been conditionally accepted at another journal.
Funny, his papers get refereed in 3-6 months and mine took over a year, and only then after pestering editors.
The condition? He has cited my multiply rejected preprint and the editors insist that it must
be put somewhere more stable than my personal website. So I put it on arXiv. Probably I should
have demanded that they publish it.
Thus was demonstrated to me partiality in the peer-review process. It's more petty personal politics than big issue party politics.
It would go a long way to explaining a lot (Score:3, Interesting)
Re:Stop posting articles from arXiv! (Score:3, Interesting)