Heat radiations travel with a speed equal to the speed of light.
Thermal Radiation occurs through a vacuum or any transparent medium (solid or fluid). It is the transfer of energy employing photons in electromagnetic waves. Thermal radiation is a direct result of the random movements of atoms and molecules in matter.
Heat radiation travels at a speed of 3×108 m/sec. Therefore, it follows a straight-line path.
Speed of light
The value for the speed of light in a vacuum is now defined as exactly 299,792,458 metres per second. Thus, the speed of light is considered a fundamental constant of nature.
In the famous relativity equation, E = mc2,
the speed of light ( c ) serves as a constant of proportionality, linking the formerly disparate concepts of mass ( m ) and energy ( E ).