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The End Of Gravity As a Fundamental Force
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."
But it sure sounds promising.
I couldn't begin to assess how plausible this theory is; neither could most of the people on Slashdot. However, I do know the arXiv is not a peer-reviewed journal, which mean that we can't even rely on the peer-review system to gain information on how sound the underlying research is. Many excellent publications appear on arXiv before being published in excellent journals, but some fairly questionable research ends up there as well.
Rather than post completely uninformed comments on the subject, leave that to people in the field.
So if this is the future...where's my jet pack?
At least half the comments on this story will boil down to one or more of the following:
There. That should save everyone some time.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
Lubos Motl (string theorist, formerly at Harvard), has recently blogged about this: http://motls.blogspot.com/2010/01/gravity-as-holographic-entropic-force.html. His conclusion is "I remain undecided".
I do like the idea of not needing an explanatory tool like "Dark Energy" ... that has always bothered me. Far more than "Dark Matter".
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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.
The World Wide Web is dying. Soon, we shall have only the Internet.
"shut up and calculate" is attributed to David Mermin according to Wikipedia (which sites an article behind a login)
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.
*EVERYTHING* in the universe is based on some fundamental thing which we "cannot detect the source of". Even something as simple as math, or logic, is based on a set of axioms, or givens, which can never, themselves, be explained in terms of where they come from.
In physics, things like quarks (or if there's something that makes those, then that thing), or the fundamental forces, are all currently unexplained regarding why or how they exist.
What this work does (or at least, claims to do) is connect gravity with the rest of physics.
But your opening line is actually quite wrong:
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.
Not at all. Presently, gravity is an axiom. It is a thing that exists, and upon which much is built, but below which nothing can be known. With this theory, gravity is just like things built upon gravity (such as orbits, gravitational singularities, etc.), which can all be explained by something below them. At some point, everything ends up as an axiom. This theory removes one of science's present axiom, and any time you can do that, you've done nothing less than fundamentally enhanced our understanding of the universe.
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.
You're muddling the distinction between the concept of exact measurement with exact model.
When we say that Newtonian physics is "about" right, we're saying that, given the properties of the area of the physical world we inhabit (about sea level on an Earth sized planet), Newtonian physics is a model that can predict the behavior of bodies in motion pretty accurately. Relativity theory models those same bodies more accurately, and in a wider area of application. In this way, our models of the universe could be said to be asymptotically approaching "correctness".
When we say that the speed of light is "about" 3 x 10^8 m/s, everybody but the most retarded physics students know that it's not exactly that, but that that number is close enough that it's usable. Same as saying pi = 3.141 and g = 9.81 ms^-2 at sea level on Earth. Those are imprecise but "close enough" approximations of natural constants which do not have integer values, so we just truncate them to the desired level of accuracy for the current use. I don't need pi to a hundred places to be able to triangulate the hats on the sports oval for the experiment in 10th grade. Hell, pi to eleven places will calculate Earth's circumference to within a millimeter, which is "accurate enough" for pretty much all everyday uses.
Don't mix these two concepts, a model can be 100% accurate even if we are incapable of measuring fully, and vice versa.
I hate printers.
Will science leave me anything I learned in class ?
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
The one funny thing about the way the majority of people use math, "close does count", until you get to a certain advanced point. Then we say "this works for all but a few special cases... close enough"
Obviously Newtonian gravity is much more understandable to your average person than say general relativity and also offers a good aproximation of expected behaviors of the physical world.
I'd say there is a good chance it is all one Unified Field. When including torque in Einstein's equations (and not assuming you are locked on the spinning object), this guy's solution works from the micro to the macro. Check it out.
http://www.theresonanceproject.org/
Indeed. The truth is, it is all a dream. My dream, in fact. It all emanates from me, I designed it all based on what you know as mathematical principles.
That assertion can also never be proved wrong, and it is mathematically sound.
You're pretty confident for a figment of my imagination....
WARNING! This girl exceeds the MAXIMUM SAFE standards established by the FDA for BRATTINESS
No kidding. Chicks really dig my emergent phenomenon.
...but they always get deeply disappointed at the microscopic reality :(