How much energy is in the Universe as photons?
116671
How much light is there in space and how heavy is it?
54501
What is the entropy of the universe today?
152130
Maximum size of the observable universe?
150075
Are photons electromagnetic waves, quantum waves, or both?
11053
Planck's Law in terms of wavelength
68726
Does photon have size measurement because of its particle nature
148751
Which is the lightest thing in this universe? Is that a photon or neutrino?
20412
Frequency of a photon
85582
Why aren't all photons virtual particles even in the "vacuum" of empty space?
91061
How much energy does the Earth absorb when a gravitational wave passes through it?
157091
Photons in coulomb field
67701
The energy of an electromagnetic wave
88577
How is light produced?
146039
Is it always possible to define energy of a system?
147954
Relation between power and energy
79614
Many-worlds: Where does the energy come from?
81503
Do photons truly exist in a physical sense or are they just a useful concept like $i = \sqrt{-1}$?