Thus, the pictures show that on Earth, warm fluid rises to the top and curling back down to stir the entire volume, while in space the warm area grows slowly by conduction and diffusion. How heat moves In school, most of us learned that heat moves by conduction, convection, and radiation. The third is not. And there is a fourth method that we usually are not taught. Conduction involves solid objects touching each other.
Heat is just atoms and molecules in motion.
In a solid, they vibrate in place and bump each other, so heat transfers slowly. Convection involves liquids flowing in a container. That makes the hot fluid less dense than the cold fluid, and the cold fluid slides under, pushing the hot fluid to the top. Radiation involves electromagnetic radiation, light waves, being emitted by one body and absorbed by another, like holding your hand in the sunlight. Since nothing is heavier or lighter, nothing falls and everything floats.