I've always found cosmology intriguing --- though not alas enough to actually learn any properly. Much out there in the field seems solidly based (if too detailed for a casual enquirer to grasp properly), and I'm pretty sure I could get to grips with it if sufficiently motivated --- the Standard Model being a case in point. Much else is patently crank, generated by individuals with impaired judgement --- we might not always agree about individual cases here --- String Theory, anyone? Very occasionally though I encounter something genuinely shocking --- so improbable and outrageous that I become aware of an emotional reaction, attempting to suppress it from consciousness --- general relativity and quantum mechanics come to mind here, when first met long ago. And perhaps more recently, the original (quaternion) formulation of the Maxwell equations. But now Jacobson, Verlinde & Co. are rattling the bars of my comfortable worldview again, and folks, I'm reeling somewhat. Tell me it ain't so --- space just the grin on another Cheshire cat? How can Lorentz transformations occur --- space and time axes finally interchanging in the proximity of the Schwarzschild radius --- if spacetime is asymmetrical? Do these ideas explain why space has just three dimensions --- never mind about a single time? Have they any relevance to the missing mass problem? Somebody, help! Fred Lunnon On 7/16/10, Henry Baker <hbaker1@pipeline.com> wrote:
The paper: http://arxiv.org/abs/1001.0785
I read over the paper, and it is surprisingly readable for mere mortals.
I don't know enough physics to comment on its accuracy as a model of the "real" world, but even as an abstract model it is very beautiful.
Basically, Verlinde turns Bekenstein on his head. Verlinde rearranges the world so that gravity falls out of information/entropy instead of the other way around.
Bekenstein showed that the universe is "holographic", meaning that _all_ the information about what is going on within a simple region of space is encoded in bits on its surface, and the _amount_ of such information is proportional to its surface area.
Verlinde goes backwards and shows that gravity is an emergent concept from the statistics of microstates. The closest high school physics analog is an osmotic force across a membrane: the force arises because it is far more probable that the more concentrated fluid becomes less concentrated than the other way around.
Interestingly, the Heisenberg constant h plays very little part in Verlinde's derivation, which treats entropy, temperature, etc. as continuous variables. This makes a lot of sense, as gravity itself is a macroscopic phenomenon.
From a blog about Verlinde's paper:
http://motls.blogspot.com/2010/01/erik-verlinde-comments-about-entropic.html ...