# Professor Stephen Hawking, 1942 - 2018

15 March 2018

Professor Stephen Hawking, 1942-2018

On 13 March 2018, physicists awoke to news that Prof Stephen Hawking, surely Oxford’s best known physics undergraduate (Univ. 1959), had died peacefully in his sleep. He leaves behind a monumental legacy.

As a graduate student, then researcher, in 1960’s Cambridge, Hawking built on the global methods introduced into relativity by Roger Penrose (Emeritus Rouse Ball Professor of Mathematics at Oxford University). Penrose had shown that black hole point-singularities formed under very general and very realisable physical conditions. Hawking went on to demonstrate that the same was true, in a time-reversed sense, of the Universe as a whole, thereby effectively proving that the Universe began in a singular state---the Big Bang. The two later collaborated on a very general approach, subsuming earlier work, for conditions under which spacetime singularities form. Before the singularity theorems, black hole research in particular had a somewhat dubious quality: a serious-minded theorist did not spend time worrying about black holes. After the Hawking and Penrose work, a golden age of black hole research came into being with the discovery and proof of many now famous results (e.g. “no hair theorems”). Black hole research drew the attention of theoretical physicists, like, well, a black hole.

While the singularity work was a technical triumph, Hawking’s greatest conceptual breakthrough occurred in 1974, when he showed that, despite the moniker, black holes are not actually black. They shine. Quantum field theory, when applied rigorously in the vicinity of a black hole event horizon, leads to the inescapable conclusion that the hole emits photons like a perfect blackbody. Just a tiny fraction of a degree above absolute zero for a hole with the mass of the sun, but a thermal blackbody nevertheless, so that black holes have a temperature, an entropy, and are intimately connected to areas of physics seemingly very different from pure gravitation. Since black holes lose mass via their thermal emission, they must also eventually evaporate: a black hole is not forever. Black holes are now thought by many to be essential to self-consistent formulations of modern string theory.

Stephen Hawking struggled almost all of his adult life with motor neuron disease, a story that is well-known and documented in the recent award-winning film, The Theory of Everything. The irresistible combination of intellectual brilliance and monumental achievements in the face of crippling physical hardship transformed Hawking into a unique iconic figure in popular culture, rivalled in renown as a physicist only by Albert Einstein in recent history. Despite huge practical and logistical difficulties, Hawking clearly enjoyed the limelight and the opportunity it afforded to express his views, and to weigh-in on a variety of current topics. He was a great inspiration to those with physical afflictions as well as to generations of young up-and-coming physicists who wanted to do physics just like Stephen Hawking. Born in the 300th anniversary year of Newton’s birth (1942) and sharing Einstein’s lifetime duration precisely (76 years), Stephen Hawking will leave a legacy that will, like those of his two greatest heroes, be felt for centuries.