Stephen Hawking, one of the world's most famous scientists, died Wednesday. Hawking was an astrophysicist who studied cosmology, the science of the origin and development of the universe. In addition to his research prowess, Hawking wrote popular books about cosmology for the public. For many, he was the first person to come to mind when asked to name a scientist.
Hawking entered graduate school at Cambridge University in England in 1962. He began studying gravity and its role in the structure of the universe. Gravity is the force that attracts objects to one another. Gravity is especially strong in areas of space called black holes, which Hawking spent much of his life studying. The gravity in a black hole is so powerful that nothing—not even light—can escape from it.
When Hawking was in school, astronomers had predicted the existence of black holes. They believed that a black hole would form when a star exploded and then collapsed in on itself. But no one had ever seen a black hole through a telescope. It wasn't until the 1970s that astronomers found evidence that black holes were in the universe. Hawking’s work helped scientists better understand this unusual space phenomenon.