Re: [math-fun] dumb question about general relativity
Re time reversal: The fact that in our neighborhood in spacetime we see stars radiating only in positive time -- and all the entropic consequences of this -- is usually attributed to initial conditions, not to any actual "law" of physics. (The Ehrenfest urn model is usually considered a good microcosm of thermodynamics, and shows time reversal symmetry.) It's just a guess, but it seems likely to me that we are aware of only a small or infinitesimal fraction of the universe, and that some other time and place have stars radiating in negative time. (Or is it possible that entropically opposite parts of the universe somehow always end up pinching off from each other by black holes?) --Dan _____________________________________________________________________ "It don't mean a thing if it ain't got that certain je ne sais quoi." --Peter Schickele
From: Dan Asimov <dasimov@earthlink.net> To: math-fun <math-fun@mailman.xmission.com> Sent: Friday, July 24, 2009 3:40:24 PM Subject: Re: [math-fun] dumb question about general relativity Re time reversal: The fact that in our neighborhood in spacetime we see stars radiating only in positive time -- and all the entropic consequences of this -- is usually attributed to initial conditions, not to any actual "law" of physics. (The Ehrenfest urn model is usually considered a good microcosm of thermodynamics, and shows time reversal symmetry.) It's just a guess, but it seems likely to me that we are aware of only a small or infinitesimal fraction of the universe, and that some other time and place have stars radiating in negative time. [What exactly does this mean? How do you experimentally determine whether your stars are radiating in positive or negative time? -- Gene] (Or is it possible that entropically opposite parts of the universe somehow always end up pinching off from each other by black holes?) --Dan
On Fri, Jul 24, 2009 at 3:51 PM, Eugene Salamin<gene_salamin@yahoo.com> wrote:
[What exactly does this mean? How do you experimentally determine whether your stars are radiating in positive or negative time?
To detect a star radiating in positive time, you point an uncharged CDS cell at the sky and look for excitations. To detect a star radiating in negative time, you'd point a charged CDS cell at the sky and look for holes. -- Mike Stay - metaweta@gmail.com http://math.ucr.edu/~mike http://reperiendi.wordpress.com
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Dan Asimov -
Eugene Salamin -
Mike Stay