On 4/10/2014 7:06 AM, Henry Baker wrote:
I did a Google search on "photon conservation" & came up with nothing (there were discussions of _preserving_ as many photons as possible in detectors, but that was completely different).
If there is such a notion of photon conservation, that would be a valuable insight.
Of course photon number isn't conserved; they're created in charged particle collisions for example. But in the expansion of the universe example they are not interacting with anything - they're just following a null geodesic in spacetime. Brent
Do you have any links or references?
At 11:14 AM 4/9/2014, Eugene Salamin wrote:
As the universe expands, the number of photons is conserved, and the wavelength of each photon lengthens proportionally to the expansion.
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