Why aren't all photons virtual particles even in the "vacuum" of empty space?
104657
Wave/particle duality
8077
Photons in expanding space: how is energy conserved?
35409
Massless charged particles
149882
What is meant by "Nothing" in Physics/Quantum Physics?
30745
Why can't photons have a mass?
1613
Is temperature in vacuum zero?
144698
Why do many people say that virtual particles do not conserve energy?
22988
Are vacuum fluctuations really happening all the time?
158809
What is the status of massless photons traveling through a medium?
12916
How does a photon experience space and time?
7332
Is the double-slit experiment typically carried out in a vacuum?
116871
Do photons take all paths or not?
13251
Does a photon in vacuum have a rest frame?
55085
How come a photon acts like it has mass in a superconducting field?
69983
Photon energy - momentum in matter
54193
Can light exist in $2+1$ or $1+1$ spacetime dimensions?
98389
Electromagnetic waves in vacuum