Stephen Hawking probed the very limits of human understanding both in the vastness of space and in the bizarre sub-molecular world of quantum theory.
As well as numerous best-selling books, Hawking also published several important scientific papers during an illustrious research career.
Through his groundbreaking theories, the legendary physicist examined the origins of the universe and helped explain the behaviour of black holes.
Stephen Hawking was a world-renowned theoretical physicist, well-known for his book A Brief History of Time, which has sold more than 10 million copies since its publication in 1988
1970: Space-time in black holes
One of Hawking’s first key ideas was how space and time react within the brutal confines of black holes.
Black holes are regions of space with a gravitational field so intense that no matter or radiation can escape.
The objects are so powerful they bend time and space in bizarre ways, and in 1970 Hawking showed how black holes alter ‘space-time’.
1971-72: Black hole mechanics
Hawking devised the second law of black holes, which states that the total surface area of a black hole will never get smaller.
In separate work, Hawking sparked the ‘no hair’ theorem of black holes.
This states that black holes can be characterised by three numbers – their mass, charge and angular momentum.
The ‘hair’ in Hawking’s idea is other information that disappears when it falls into the black hole.
1974-75: How black holes vanish
Hawking showed that black holes emit heat and eventually vanish in an extremely slow process.
While a black hole with the mass of the sun would take longer than the age of our universe to evaporate, smaller ones disappear faster.
Near the end of their lives they release heat at a dramatic rate, with an average-sized black hole releasing the energy of a million hydrogen bombs in just a tenth of a second.
1982: How galaxies arise
Hawking was one of the first to show how galaxies may have formed during an explosion of time and space.
He found that quantum fluctuations – tiny variations in the distribution of matter – grew into the galaxies that dot the cosmos today.
This is because strong gravitational forces made matter clump together.
1983: How the universe began
Hawking is best known for his attempts to combine two key theories of physics: Quantum theory and Einstein’s general relativity.
In 1983 the physicist partnered with Chicago University’s Professor Jim Hartle to propose a ‘wave function of the universe’.
Known as the Hartle-Hawking state, this notion is meant to figure out how the universe began through quantum mechanics.
In theory, this could be used to understand the properties of the universe around us.
1988 A brief history of time
Hawking’s bestselling book A Brief History of Time has sold more than ten million copies since it was published in 1988.
The book, which described the structure, origin, development and eventual fate of the universe, was a surprise success for the relatively unknown physicist, staying in the Sunday Times bestseller list for 237 weeks.
Hawking wrote the book for readers with no knowledge of any scientific theories.