Stephen Hawking

Stephen Hawking was a British theoretical physicist and cosmologist whose work on black holes and on the origin of the universe made him one of the most widely known scientists of his time. He wrote popular books on cosmology, and he became a symbol of the triumph of the mind over physical disability.

Early Life and Education

Hawking was born in Oxford in 1942 and studied physics at University College, Oxford. He then went to Cambridge to work on cosmology, and he began doctoral research under Dennis Sciama.

He was diagnosed with a motor neurone disease at the age of twenty-one, and he was given only a few years to live. The disease progressed, and he eventually became almost completely paralysed.

He completed his doctorate and was appointed to a research fellowship. He used a wheelchair and later communicated through a speech synthesizer, and he continued to work and to travel.

Black Holes and Cosmology

Hawking's early work concerned the singularities of general relativity. He showed, with Roger Penrose, that the theory implies that the universe must have had a beginning in a singularity.

He then studied the thermodynamics of black holes and discovered that they emit radiation, a result now known as Hawking radiation. The discovery implied that black holes are not entirely black and that they can evaporate.

The result raised deep questions about the relation between general relativity and quantum mechanics. It became a central problem of theoretical physics.

The No-Boundary Proposal

Hawking worked with James Hartle on a proposal for the origin of the universe. They suggested that the universe has no boundary in time, in the same way that the surface of the earth has no edge.

The proposal uses the methods of quantum gravity and Euclidean space-time. It implies that the question of what happened before the beginning of the universe is not well posed.

Hawking also wrote on the arrow of time and on the interpretation of quantum mechanics. He argued that the universe can be described by a single wave function.

Popular Writing and Fame

Hawking's book A Brief History of Time, published in 1988, became an international bestseller. It explained cosmology to a general audience and made him a celebrity.

He wrote further books, including The Universe in a Nutshell and The Grand Design, and he gave many public lectures. He held the Lucasian Chair of Mathematics at Cambridge.

He appeared in popular culture and campaigned on issues of science and of disability. He died in Cambridge in 2018.

Legacy

Hawking's scientific work opened new directions in the study of gravity and of quantum theory. His result on black hole radiation is regarded as one of the most important theoretical discoveries of the twentieth century.

He is also remembered for his communication of science to the public. His books and lectures reached millions of readers.

He remains a symbol of the power of the intellect and of the human capacity to overcome adversity. His contributions continue to shape research in cosmology.

The Early Cosmological Work

Hawking's doctoral thesis concerned the properties of expanding universes. He worked with Roger Penrose on the singularity theorems, which showed that the general theory of relativity implies that the universe began in a state of infinite density.

The theorems were a major result, because they showed that a beginning was not merely an artefact of the symmetry of the models. The work earned him a reputation as one of the leading young cosmologists.

He also studied the perturbations of the early universe and the formation of structure. He was appointed to a research fellowship and then to a lectureship at Cambridge.

Quantum Mechanics and Gravity

Hawking sought to combine the theory of gravity with quantum mechanics. He applied quantum field theory to the curved space-time around a black hole.

The calculation showed that a black hole should emit particles with a thermal spectrum, and that it should therefore have a temperature and an entropy. The result unified the laws of thermodynamics with the geometry of space-time.

The evaporation of black holes raises the information paradox, the question of what happens to the information that falls into a black hole. The problem remains unsolved and is a central concern of theoretical physics.

The Origin of the Universe

The no-boundary proposal, developed with James Hartle, describes the origin of the universe in terms of a wave function. The proposal implies that the universe has no boundary in time and that the question of what happened before the beginning is not meaningful.

Hawking also worked on the inflationary model of the early universe and on the anisotropy of the cosmic microwave background. He made contributions to the theory of the very early universe.

He debated the interpretation of quantum mechanics with other physicists and defended the view that the theory describes the world as it is. He was a critic of the many-worlds interpretation.

Popular Science and Public Life

A Brief History of Time was written for a general audience and became one of the best-selling science books ever published. It has been translated into many languages.

He wrote further popular books and gave lectures throughout the world. He appeared on television and in films, and he became a familiar figure in popular culture.

He campaigned on issues of science, of education, and of disability. He warned of the dangers of artificial intelligence and of contact with extraterrestrial life.

Recognition

Hawking received many honours, including the Copley Medal of the Royal Society and the Presidential Medal of Freedom. He was elected a Fellow of the Royal Society and a member of the Pontifical Academy of Sciences.

He held the Lucasian Chair of Mathematics at Cambridge, a post once held by Isaac Newton. He was appointed Companion of Honour in 1989.

His ashes were interred in Westminster Abbey between the graves of Newton and Darwin. His life has been the subject of films and of biographies.

See also

• Black hole thermodynamics
• Physical cosmology