Stephen Hawking was a physicist who studied black holes and the origins of the universe, becoming one of the most famous scientists of his time. His theoretical discovery that black holes slowly emit radiation and can eventually evaporate, now called Hawking radiation, is considered one of the most important findings in modern physics. He was diagnosed with a disease that slowly took away his ability to move and speak, so he used a special computer voice to keep sharing his ideas. He wrote A Brief History of Time, a bestselling book that helped everyday people understand the universe.