Krzysztof Lorek, Jorma Louko, Andrzej Dragan: Ideal clocks—a convenient fiction. Classical and Quantum Gravity 32,17 (2015) 175003 sounds interesting. According to Einstein, time passes at rates that depend on the observer, but I (at rest) could compute your rate by knowing your velocity. However -- might the rate of passage of time depend not only on velocity, but also on acceleration? Well, the "Unruh effect" says an accelerating observer will perceive more thermal noise. And this noise will cause your velocity to fluctuate as thermal background photons hit you and push you around. That in turn will alter your perception of time. So, yes. And actually, just sitting on Earth I am accelerating to counteract gravity all the time (in the general relativistic view) and am indeed experiencing a slightly different rate of time versus some observer far from Earth -- although for a different reason than I just said, this is because of the non-flatness of spacetime. The Unruhish effect just mentioned goes beyond merely general relativity. It should make quantum gravity nastier.
And that is available here http://arxiv.org/abs/1503.01025 Let me now consider a stupid oversimplified scenario. Imagine a particle with the same charge as an electron existed, but at some (perhaps different) fixed rest-mass M. Assume this particle is sitting in a photon radiation blackbody bath at large temperature T. Use units with G=c=kB=hbar=alpha=1. Our particle would be subject to a fluctuating acceleration of order of magnitude a=T^P M^(-Q) caused by Compton scatterings, where the exponents P and Q are some constants. But this acceleration a in turn would cause an effective temperature T of order a, causing a new a, and so on. My question is: could this process "run away" causing exponential or super-exponential blowup of a? At least if treated as naively as I have. Answer: apparently not. I think in the ultrarelativistic asymptotic regime that the effective exponent P=-1<0 so we would not get such a problem; the universe is saved. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)
On 10/11/2015 11:19 AM, Warren D Smith wrote:
Krzysztof Lorek, Jorma Louko, Andrzej Dragan: Ideal clocks—a convenient fiction. Classical and Quantum Gravity 32,17 (2015) 175003
sounds interesting.
According to Einstein, time passes at rates that depend on the observer, but I (at rest) could compute your rate by knowing your velocity.
However -- might the rate of passage of time depend not only on velocity, but also on acceleration? In relativity duration is a geometric quantity, invariant interval measured along any time-like path. So acceleration affects it just at the curvature of a path between two points affects its length.
Well, the "Unruh effect" says an accelerating observer will perceive more thermal noise. And this noise will cause your velocity to fluctuate as thermal background photons hit you and push you around. That in turn will alter your perception of time.
This is a different, non-geometric effect due to the quantum vacuum. Brent
So, yes.
And actually, just sitting on Earth I am accelerating to counteract gravity all the time (in the general relativistic view) and am indeed experiencing a slightly different rate of time versus some observer far from Earth -- although for a different reason than I just said, this is because of the non-flatness of spacetime.
The Unruhish effect just mentioned goes beyond merely general relativity. It should make quantum gravity nastier.
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Warren D Smith