A Black Hole is a Star Forever Falling Inward

He talked to us about the new theory of black holes which he had then just worked out. The idea of a black hole was one of the most dramatic consequences of Einsteins theory of gravity. According to Einstein's equations, a massive star at the end of its life, when it has exhausted its nuclear fuel, continues to contract and grow smaller and denser under the influence of its own gravitation. After the nuclear fuel is used up, the star goes into a state of gravitational collapse. All parts of t...

 Einstein's Cosmological Constant

Georges Lemaitre was a pudgy, pinkish Belgian Jesuit abbe—a Catholic priest—who also happened to be a skilled astronomer. Lemaitre had noticed that Einstein's general theory of relativity would have implied that the universe was expanding but for a troublesome little mathematical term called the cosmological constant that Einstein had inserted into his equations. Lemaitre saw no convincing reason why the cosmological constant should be there. In fact, Einstein himself had originally calc...