So all objects vibrate or move to a certain extent, and therefore all objects at all times radiate energy. Okay? One cool thing about radiation, unlike convection or conduction, is that radiation can occur in the absence of molecules or in the absence of a physical barrier. And this is seen in space when light travels from the sun, the hot object to the Earth, the cooler object, the waves travel in a vacuum in the absence of molecules. And that's because waves, electromagnetic waves, are actually energy bundles that carry themselves from a hot object to a cool object, okay? And it is radiation that heats the Earth.