Radio waves are bounced off an object, and the time at which the echo is received indicates its distance. A way in which energy is transferred from place to place in the form of a wave.
Light is a form of electromagnetic radiation.
The transfer of momentum carried by electromagnetic radiation to a body that the radiation impinges upon. The release of energy by rare, heavy elements when their nuclei decay into lighter nuclei. A mathematical proportionality, arising from Stefan's Law, which allows astronomers to indirectly determine the radius of a star once its luminosity and temperature are known. A giant star whose surface temperature is relatively low, so that it glows with a red color. The section of the evolutionary track of a star that corresponds to continued heating from rapid hydrogen shell burning, which drives a steady expansion and cooling of the outer envelope of the star.