The velocity of heat radiation in a vacuum is
(1) Equal to that of light
(2) Less than that of light
(3) Greater than that of light
(4) Equal to that of sound
Answer: (1) Electrons are generally responsible for heat conduction. The phonons (vibrations of the nuclei) also play a part, depending on the temperature of the medium. It depends on the specific conductor you’re using. At some point, in a vacuum, the electrons have to be excited enough to spit out photons, which are Electromagnetic radiation, which in a vacuum should go on forever at the speed of light theoretically.
