Is the energy from redshifting lost or destroyed?

Question

In cosmological redshifting, photons lose energy because of the expansion of the universe.

Bur what actually happens to this energy? Is it just “lost” or is it physically destroyed (which would seem impossible)? If it is lost, what is it lost to or what does it become?

In: 258

Answer 1

Neither. It’s conserved. Think like taffy. If you have a 1cmx1cm cut of taffy then stretch it out to 2cmx2cm, do you have more or less taffy? Neither, you have the exact same amount of taffy as you had before, it’s now just stretched out. Easier to chew through a corner of a 2cmx2cm cut of taffy than a 1cmx1cm cut of taffy.