Gravity

Impact craters are made when a space rock (called a meteorite or asteroid) hits a rocky planet or moon. The impact makes a round hole in the surface, called a crater.

A satellite is an object which orbits another. An orbit is the curved path that an object in space takes around another object.

You have likely heard about the Universe expanding. Or that redshift can tell us about the movements of galaxies. Both are difficult ideas to imagine and understand.