Stephen Hawking didn't create any physical inventions, but he came up with several insightful theories in cosmology. He developed theories about black holes, including the second law, which states that a black hole never reduces in surface area as far as classical physics is concerned. This law suggests that black holes are hot.
Hawking also theorized on the "no-hair" concept of black holes, which characterizes black holes by their mass, angular momentum and charge. He used quantum theory to show that a black hole could vanish and that it emits heat, contrary to the previous belief that nothing could escape a black hole. He suggested that it would take longer than the age of the universe for a black hole of the same mass as the sun to disappear. His theory holds that once a black hole develops, it radiates energy and starts to lose mass. The radiation offers no information on the content of a black hole, and once the black hole vanishes, all the information is lost. Hawking was the first to show how galaxies might arise from quantum fluctuations. He also attempted to develop a quantum theory of gravity that applies to black holes. Hawking’s publications include “A Brief History of Time: From the Big Bang to Black Holes” and “Stephen Hawking's Universe: The Cosmos Explained.”