As part of the Science Museum’s celebration of Stephen Hawking’s 70th birthday, leading contemporaries have paid tribute to his remarkable impact on the field of cosmology.
Hawking, director of research at the University of Cambridge’s Department of Applied Mathematics and Theoretical Physics, has seen cosmology rise from a niche subject in the 1960s to being perhaps the most compelling of all the sciences – not least thanks to his own inspirational contribution.
One of Hawking’s overarching goals has been to take general relativity (Einstein’s law of gravity), which controls the large scale structure of the universe, and blend it with quantum theory, which rules the world of atoms, molecules and the very small, to produce a grand theory of everything, known as quantum gravity.
Hawking first caught the attention of his peers in the late 1960s, working with Roger Penrose on how general relativity sometimes breaks down, resulting in something called a singularity. They showed that such singularities must occur inside black holes – and, most probably, at the start of the universe. This idea implies that singularities mark the beginning and end of space and time, which was created during the Big Bang and breaks down within black holes.
In his most famous work, celebrated in a 70th birthday gift from the Museum, Hawking raised the intriguing possibility that black holes are not as black as once thought. The reason is down to one strange consequence of quantum theory: empty space isn’t empty at all: pairs of particles are constantly popping into and out of existence. If they appear on the border of event horizon – the point of no return from the gravity well of a black hole, as described by general relativity – they may find themselves on different sides, with one sucked in, and the other becoming part of “Hawking radiation”.
The same mathematics can also be applied to the ‘echo of the Big Bang’ which took place 13.7 billion years ago, the splash of residual microwaves that still warm today’s universe, and to the way in which a soup of ultra-hot matter crystallised to form the visible universe.
In spring 1982, Hawking made a bold proposal: that fluctuations in the cosmic background radiation could be traced back to Hawking radiation, as the tiny seeds around which the large scale structure of the universe coalesced.
That summer, this “fluctuation theory” was developed at a workshop organised by Hawking and his colleague Gary Gibbons. Remarkably, their efforts – and those of two Russians who came up with the same result independently – predicted these fluctuations in the fabric of the cosmos a decade before a purpose-built satellite called COBE observed them in the heavens.
Leading figures remark:
“Hawking’s revolutionary discovery that black holes radiate was the first spectacular result in quantum gravity, suggesting a startling unification of space-time, quantum mechanics and thermodynamics that has set much of the agenda for fundamental physics in the past four decades. It is impossible to overstate how profound these ideas are, how influential they have been, and how they continue to drive our 21st century quest to more deeply understand the nature of space-time and quantum mechanics.”
Nima Arkani-Hamed, Institute for Advanced Study,Princeton, front rank theoretician
Stephen Hawkings’ discovery of black hole evaporation was a very special insight. By now it influences work in many areas of physics — heavy ion physics, quantum critical phenomena in condensed matter physics, cosmology, and of course the search for a fundamental understanding of quantum gravity, which was Stephen’s original motivation. After almost forty years that Stephen’s discovery has been a source of fresh thinking, we still are far from really getting to the bottom of things. So we still need Stephen’s insights! Happy Birthday, Stephen! There is a lot to celebrate and I wish I could be present for this occasion.
Edward Witten, Institute for Advanced Study,Princeton, string theory pioneer
“Stephen Hawking’s name will life in the annals of science because he has probably done as much as anyone else since Einstein to extend our grasp of gravity, space and time; millions have had their cosmic horizons widened by his bestselling books; and even more, around the world, have been inspired by a unique example of achievement against all the odds-a manifestation of amazing willpower and determination. His “three score years and 10″ deserve all the accolades they are getting.”
Martin Rees, University ofCambridge, Astronomer Royal
The most spectacular of Hawking’s discoveries was the emission of radiation from black holes. This caused a fundamental advance in our understanding of gravitation and thermodynamics. The Hawking equation, telling us that the entropy of a black hole is proportional to the area of its horizon, is as important as the Einstein equation telling us that the energy of an object is proportional to its mass.
Freeman Dyson, Institute for Advanced Study, mathematical physicist and pioneer of quantum electrodynamics
Stephen Hawking himself remarks:
“ It has been a glorious time to be alive and doing research in theoretical physics. Our picture of the universe has changed a great deal in the last 70 years, and I’m happy if I have made a small contribution.”
The below film features Stephen Hawking talking about the new display at the Science Museum alongside exclusive photos from his family archives and lifelong works.