He discovered that black holes emit radiation, now called Hawking radiation, fundamentally changing theoretical physics by uniting general relativity with quantum mechanics.

Stephen Hawking was an English theoretical physicist and cosmologist who served as director of research at the Centre for Theoretical Cosmology at Cambridge University. Diagnosed with motor neurone disease (ALS) in 1963 at age 21, he defied a two-year prognosis to live 55 more years, revolutionizing our understanding of black holes and the universe while paralyzed and communicating through a speech-generating device. His book A Brief History of Time spent a record 237 weeks on bestseller lists, and he received the Presidential Medal of Freedom along with dozens of scientific honors before his death on March 14, 2018, at age 76.

Born in Oxford on January 8, 1942, Hawking grew up in St Albans where his eccentric family ate meals in silence while reading books and traveled in a converted London taxicab. He studied physics at University College, Oxford, earning a first-class degree in 1962 before beginning graduate work at Trinity Hall, Cambridge. At age 21 in 1963, doctors diagnosed him with amyotrophic lateral sclerosis and gave him two years to live, but the disease progressed far slower than expected, gradually paralyzing him over five decades while leaving his brilliant mind untouched.

Hawking married Jane Wilde in 1965, two years after his ALS diagnosis, and she supported him through decades of declining mobility as they raised three children: Robert, Lucy, and Timothy. The strain of caregiving contributed to their divorce in 1995, and he married his nurse Elaine Mason the same year before divorcing her in 2006. After losing his speech in 1985 following a tracheotomy, he communicated through a speech synthesizer controlled first by a handheld switch and eventually by a single cheek muscle, and this synthetic voice became his iconic trademark heard in lectures, television appearances on The Simpsons and Star Trek, and even on a Pink Floyd album.