- #1
Adrian Baker
- 378
- 2
We are told that as the Universe expands, the 'temp' of it cools and we now have the microwave background radiation as a remnant. Fine.
Considering the energy density of the universe, energy is indeed conserved as it expands and cools.
However, what about an individual photon, who's energy is given by E=hf. Its wavelength has increased due to the expansion of spacetime, reducing its frequency, and hence its energy.
Where did its energy go?
Considering the energy density of the universe, energy is indeed conserved as it expands and cools.
However, what about an individual photon, who's energy is given by E=hf. Its wavelength has increased due to the expansion of spacetime, reducing its frequency, and hence its energy.
Where did its energy go?