I think that the expansion of the universe gives an apparent red-shift, independent of any special relativistic Doppler shifts. For example, the cosmic microwave background spectrum is certainly cooler (lower frequency) than it was at recombination. Bill C. -----Original Message----- From: math-fun-bounces@mailman.xmission.com [mailto:math-fun-bounces@mailman.xmission.com] On Behalf Of Adam P. Goucher Sent: Wednesday, April 09, 2014 10:30 AM To: math-fun Subject: [EXTERNAL] Re: [math-fun] What if Turing/Shannon/Bekenstein were wrong? "...and the light becomes redder." Are you sure about that? I don't think the inflation of the universe would alter the wavelength of a photon; that seems utterly impossible. Red-shift is a relativistic effect, namely that if two observers are travelling at different speeds, they will disagree what wavelength a particular photon has. This is totally unrelated to the inflation of the universe. Sincerely, Adam P. Goucher
----- Original Message ----- From: Henry Baker Sent: 04/09/14 04:49 PM To: Eugene Salamin, math-fun Subject: Re: [math-fun] What if Turing/Shannon/Bekenstein were wrong?
I don't see how it is possible for the number of photons to be conserved as the universe expands.
Experiment #1. Flat 3D space; no expansion.
A flash of green light at the origin expands in a spherical shell (as is usual in odd-dimensional spaces).
The intensity of this green light goes down as 1/r^2 as the spherical shell of radius r expands, but the light remains exactly the same green color.
The number of photons is conserved.
Experiment #2. Flat, but expanding 3D space.
A flash of green light at the origin expands in a spherical shell, and the light becomes redder.
Since red photons have less energy than green photons, there must be more of them to conserve the same energy from the initial flash.
QED
At 04:45 PM 4/8/2014, Eugene Salamin wrote:
No, as the universe expands, the number of photons is conserved.
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun