text: how does the sun's energy leave the earth? the energy from the sun must be leaving the earth at the same rate it is being absorbed by the earth, or the energy would build until the planet vaporized.  so how is it exiting?  sunlight is absorbed by the earth and mostly turned into heat, but i wouldn't think heat could leave the planet as the vacuum of space should act as an insulator.  how is all the energy escaping, and in what form? you are absolutely right---there is a balance between energy in and energy out from the earth that keeps the total energy content of the earth (and therefore its temperature) approximately constant.  the energy inputs are: 1) solar heating, primarily at wavelengths between 0.5 microns and 2 microns. 2) radioactivity inside the earth---this keeps the interior molten and powers volcanos 3) kenetic energy from meteorite imacts. 4) kenetic energy of solar wind particles 5) plasma waves in the ionosphere, excited by the solar wind 6) absorption of high-energy particles (cosmic rays) from the sun, the galaxy, and extragalactic sources. of these, the first is by far the most important.  the energy outputs are: 1) radiation by the earth's atmosphere at wavelengths between 5 microns and 100 microns. 2) reflection of sunlight from clouds and water 3) evaporation of gasses into interplanetary space from the upper atmosphere. 4) plasma waves in the ionosphere. 5) a small neutrino flux emitted by radioactive processes inside the earth of these, the first is by far the most important, and it is sensitive to the amount of greenhouse gases, co2 in particular.