Stephen William Hawking (8 January 1942 – 14 March 2018) was an English theoretical physicist, cosmologist, and author. Hawking's scientific works included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity and the theoretical prediction that black holes emit radiation, often called Hawking radiation. Hawking was diagnosed with a form of motor neurone disease that gradually paralysed him over the decades. After the loss of his speech, he was able to communicate through a speech-generating device. His book A Brief History of Time appeared on the Sunday Times bestseller list for a record-breaking 237 weeks.