National Geographic : 1989 May
2The curvature of space time produces its greatest effects aroundobjects with the most mass, such as the sun or other stars. Roll a billiard ball along the sheet in the generaldirection of a dimple, and it will dip towardthe dimple and roll away at a different angle. In the same way, the path of any form of matter or energy including light- will bend as it passes through the gravitationalfield of a massive object. Justas a ball circles endlessly within a dimple on the frictionless sheet, a planet or satellite or bits a massive object. When a star runs out of nuclear fuel, it can collapse under its own weight. As if stretchingthe sheet to infinity,gravity intensifies unimaginably,crushing atoms and trappingany matter or energy that enters. From such a black hole, not even light can escape.