developed a mathematical theory called Roche's Limit. This theory determines how close an object, like a moon, can be to a planet before gravity breaks up the object.
All objects pull on other objects. The bigger the mass, the stronger the pull. For example, the Moon pulls on Earth, causing tides in the oceans. A big enough planet or moon can make a smaller, orbiting object bulge and stretch. This stretching gets more extreme as the orbiting object comes closer to the the planet. There is a minimum distance where the force of stretching becomes stronger than the force holding the orbiting body in one piece. If it crosses this minimum distance, called Roche's Limit, the orbiting body breaks apart.
