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Share via Email Stephen Hawking at his office at the department of applied mathematics and theoretical physics at Cambridge University in Murdo Macleod for the Guardian The image of Stephen Hawking — who has died aged 76 — in his motorised wheelchair, with head contorted slightly to one side and hands crossed over to work the controls, caught the public imagination, as a true symbol of the triumph of mind over matter.
As with the Delphic oracle of ancient Greece, physical impairment seemed compensated by almost supernatural gifts, which allowed his mind to roam the universe freely, upon occasion enigmatically revealing some of its secrets hidden from ordinary mortal view.
Of course, such a romanticised image can represent but a partial truth. Those who knew Hawking would clearly appreciate the dominating presence of a real human being, with an enormous zest for life, great humour, and tremendous determination, yet with normal human weaknesses, as well as his more obvious strengths.
The scientific community might well form a more sober assessment. He was extremely highly regarded, in view of his many greatly impressive, sometimes revolutionary, contributions to the understanding of the physics and the geometry of the universe. Hawking had been diagnosed shortly after his 21st birthday as suffering from an unspecified incurable disease, which was then identified as the fatal degenerative motor neurone disease amyotrophic lateral sclerosis, or ALS.
Soon afterwards, rather than succumbing to depression, as others might have done, he began to set his sights on some of the most fundamental questions concerning the physical nature of the universe.
In due course, he would achieve extraordinary successes against the severest physical disabilities. Defying established medical opinion, he managed to live another 55 years. His background was academic, though not directly in mathematics or physics.
His father, Frank, was an expert in tropical diseases and his mother, Isobel nee Walkerwas a free-thinking radical who had a great influence on him. He was born in Oxford and moved to St Albans, Hertfordshire, at eight. He was recognised as unusually capable by his tutors, but did not take his work altogether seriously.
Although he obtained a first-class degree init was not a particularly outstanding one. He decided to continue his career in physics at Trinity Hall, Cambridge, proposing to study under the distinguished cosmologist Fred Hoyle. He was disappointed to find that Hoyle was unable to take him, the person available in that area being Dennis Sciama, unknown to Hawking at the time.
In fact, this proved fortuitous, for Sciama was becoming an outstandingly stimulating figure in British cosmology, and would supervise several students who were to make impressive names for themselves in later years including the future astronomer royal Lord Rees of Ludlow.
Sciama seemed to know everything that was going on in physics at the time, especially in cosmology, and he conveyed an infectious excitement to all who encountered him.
He was also very effective in bringing together people who might have things of significance to communicate with one another.
When Hawking was in his second year of research at Cambridge, I then at Birkbeck College in London had established a certain mathematical theorem of relevance.
This picture had been put forward by J Robert Oppenheimer and Hartland Snyder inbut only in the special circumstance where exact spherical symmetry was assumed. The purpose of this new theorem was to obviate such unrealistic symmetry assumptions. Some of the assumptions in my original theorem seem less natural in the cosmological setting than they do for collapse to a black hole.
In order to generalise the mathematical result so as to remove such assumptions, Hawking embarked on a study of new mathematical techniques that appeared relevant to the problem.
A powerful body of mathematical work known as Morse theory had been part of the machinery of mathematicians active in the global topological study of Riemannian spaces.
InWerner Israel published a remarkable paper that had the implication that non-rotating black holes, when they had finally settled down to become stationary, would necessarily become completely spherically symmetrical.
A key ingredient to the full argument was that if there is any rotation present, then there must be complete axial symmetry. This ingredient was basically supplied by Hawking in The very remarkable conclusion of all this is that the black holes that we expect to find in nature have to conform to this Kerr geometry.
As the great theoretical astrophysicist Subrahmanyan Chandrasekhar subsequently commented, black holes are the most perfect macroscopic objects in the universe, being constructed just out of space and time; moreover, they are the simplest as well, since they can be exactly described by an explicitly known geometry that of Kerr.
The life of Stephen Hawking — in pictures Read more Following his work in this area, Hawking established a number of important results about black holes, such as an argument for its event horizon its bounding surface having to have the topology of a sphere.
Yet it had seemed, on the other hand, that the physical temperature of a black hole must be exactly zero, inconsistently with this analogy, since no form of energy could escape from it, which is why Hawking and his colleagues were not prepared to take their analogy completely seriously.
Hawking had then turned his attention to quantum effects in relation to black holes, and he embarked on a calculation to determine whether tiny rotating black holes that might perhaps be created in the big bang would radiate away their rotational energy. Accordingly, any black hole actually has a non-zero temperature, agreeing precisely with the Bardeen-Carter-Hawking analogy.
This radiation coming from black holes that Hawking predicted is now, very appropriately, referred to as Hawking radiation. For any black hole that is expected to arise in normal astrophysical processes, however, the Hawking radiation would be exceedingly tiny, and certainly unobservable directly by any techniques known today.
But he argued that very tiny black holes could have been produced in the big bang itself, and the Hawking radiation from such holes would build up into a final explosion that might be observed. There appears to be no evidence for such explosions, showing that the big bang was not so accommodating as Hawking wished, and this was a great disappointment to him.
These achievements were certainly important on the theoretical side.The Skills You Need to be Promoted at Work Working in a professional environment requires you to put in hard work and deliver quantity or quality, or even both.
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