On Sunday, June 1, 2025 at 5:38:51 AM UTC-6 John Clark wrote:
On Sun, Jun 1, 2025 at 3:16 AM Alan Grayson <[email protected]> wrote: *> But the question persists; when photons redden as the universe expands, where does the lost energy go? AG* *The energy doesn't go anywhere, it's just destroyed, * * Can't those photons being reddened as the universe expands, emit energy? How can the energy go nowhere? AG* *energy is not conserved at the cosmic level. Noether's theorem says if there's a symmetry, then there's a corresponding conservation law (but the reverse does not necessarily hold, if there is a conservation law there may or may not be a corresponding symmetry). * *In the case of energy Noether says the corresponding symmetry is time, at the cosmic scale if energy is conserved then the universe should look the same from one time to another, but if the universe is expanding it doesn't look the same from one time to another, and if the universe is accelerating then time is even less symmetrical. So energy is not conserved globally, however it's still true that at the local level if things are at thermal equilibrium then the amount of energy entering a finite volume of space will equal the amount of energy leaving that volume.* *John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis>* 7ma -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/80c720b0-cf61-483a-b2e8-3258206936d4n%40googlegroups.com.
