Quanta and the conservation of energy

[diagopod]

Learning the basics of quantum theory, one thing I can't quite grasp is how quanta, especially the e=hf equation, works within the law of the conservation of energy. I imagine the heat death of the universe for example, and taken to the extreme end all masses have been converted to energy, bosons, quanta, and what we have is an ever expanding universe essentially of photons. Presumably, all those photons are stretching out as the universe expands, but given e=hf, that would mean each of those stretching (lower frequency) photons are losing energy with time, and since the universe is nothing but these photons, it would seem the entire universe would be losing energy with time. I know there's a fallacy in here somewhere. Maybe there can't be a universe just of photons? Or a stretched photon has less energy by e=hf but more potential energy that e=hf doesn't recognize? Or since photons aren't conserved each photon in the expanding universe does indeed have less energy, but there are more photons created as the universe expands, or something else? Thanks for bearing with me, appreciate any help.

 

[azntoon]

The basic law of conservation of energy states that energy can neither be created nor destroyed, it can only be transformed from one form to another. This means that the photons in the expanding universe are not actually losing energy, they are merely changing form. As the frequency of the photons decreases with the expanding universe, their energy is converted into other forms of energy such as gravity. This is why the universe is still able to maintain its total energy despite its expansion over time. The e=hf equation simply describes how energy is related to frequency, but does not itself affect the conservation of energy.