This is the website of Abulsme Noibatno Itramne (also known as Sam Minter). Comments here or emails to me at abulsme@abulsme.com are encouraged... or follow me on Twitter as @abulsme.

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My Eclipse Sequence

OK, I’m no pro, but not too horrible for a first attempt and just shooting through the filter glass in the box. Perhaps I’ll try again in 2024. :-)

Entropic Gravity?

Saw this a few days ago. I actually read the paper itself rather than just the summaries on various blogs. That is the first time I’ve done that with a physics paper in a long long time. If this pans out, and who knows if it will, but… it could be one of the biggest flips in terms of how we look at the universe and “fundamental” forces in quite awhile. Basically, it describes gravity as an emergent phenomena which rises naturally out of thermodynamic entropy effects rather than as a fundamental force of its own. This is the kind of thing that makes you go “wow” and think about things from a whole new direction. The holographic principle, which is mind blowing in its own right, is also heavily involved in the reasoning.

On the Origin of Gravity  and the Laws of Newton (pdf)
(Erik Verlinde, arxiv.org, 6 Jan 2010)

Starting from first principles and general assumptions Newton’s law of gravitation is shown to arise naturally and unavoidably in a theory in which space is emergent through a holographic scenario. Gravity is explained as an entropic force caused by changes in the information associated with the positions of material bodies. A relativistic generalization of the presented arguments directly  leads to the Einstein equations. When space is emergent even Newton’s law of  inertia needs to be explained. The equivalence principle leads us to conclude  that it is actually this law of inertia whose origin is entropic. 

Does this view of gravity lead to predictions? The statistical average should give the usual laws, hence one has to study the fluctuations in the gravitational force. Their size depends on the effective temperature, which may not be universal and depends on the effective value of ℏ. An interesting thought is that fluctuations may turn out to be more pronounced for weak gravitational fields between small bodies of matter. But clearly, we need a better understanding of the theory to turn this in to a prediction. 

It is well known that Newton was criticized by his contemporaries, especially by Hooke, that his law of gravity acts at a distance and has no direct mechanical cause like the elastic force. Ironically, this is precisely the reason why Hooke’s elastic force is nowadays not seen as fundamental, while Newton’s gravitational force has maintained that status for more than three centuries. What Newton did not know, and certainly Hooke didn’t, is that the universe is holographic. Holography is also an hypothesis, of course, and may appear just as absurd as an action at a distance. 

One of the main points of this paper is that 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. Once this is done, the mechanisms for Newton’s gravity and Hooke’s elasticity are surprisingly similar. We suspect that neither of these rivals would have been happy with this conclusion. 

(via Slashdot)

I’ll add that not only is gravity emergent…  but so is space time itself.  Uh, wow?

Good stuff.