Stephen Hawking, the famed theoretical physicist who defied a diagnosis of amyotrophic lateral sclerosis to live virtually his entire adult life with the disease – in a wheelchair and paralyzed but making constant contributions to a world few could understand – has died at age 76, a family spokesman said.

Although Hawking may have been incapacitated physically, he managed to write books, including the best seller “A Brief History of Time,” teach physics and mathematics, deliver speeches and even float in zero gravity, all while working in the fields of cosmology and quantum gravity.

Hawking reached his eighth decade, but was forced to miss a scientific debate to mark his 70th birthday in January 2012 because he was discharged from a hospital only two days earlier. His personal assistant told the Daily Telegraph at the time his speech was getting noticeably slower, sometimes only a word a minute.

NASA posted the following on Twitter: “Remembering Stephen Hawking, a renowned physicist and ambassador of science. His theories unlocked a universe of possibilities that we & the world are exploring. May you keep flying like superman in microgravity, as you said to astronauts on @Space_Station in 2014″

https://twitter.com/NASA/status/973787392590172160