Is what heats the earth the energy turned into heat from the sun, or the light hitting the earth from the sun. how does light heat anything if it has such small mass how can it excite particles. I assume that it would be the light hitting the earth heating it for obvious reasons, like seasons. but then what happens to all the thermal energy produced by the sun. would the thermal energy need a median to move through. is that why the sun is so hot to begin with there because there is nothing really for the heat to move through except low density hydrogen (space) to lose heat to, but theres not much of that around. Is it because theres not enough of a median for heat to travel to use in any noticeable amount?