Stephen
Hawking has died, leaving behind him a body of scientific work that shone a
light on the darkest parts of the universe.
The Cambridge professor and physicist became famous for his work on the
Hawking radiation that took his name. The discovery at the heart of that
phenomenon was a simple one – black holes are not completely black, but glow
with specific kinds of radiation – but it was one that entirely changed our
picture of the universe and where it was going.
Professor Hawking was famous as much for his explanations and advocacy
as he was for his work. But the work itself was profound and grand, changing
our understanding of black holes and some of the strangest phenomena in
existence.
The central part of that work was his
discoveries about Hawking radiation. That idea is still only theoretical – if
it had been proven, as it may well soon be, Professor Hawking would have
been very likely indeed to have won the Nobel prize – but it is now the
beginning of a deep and technical body of work.
Hawking radiation was first outlined in
1974. It describes strange effects that should be visible especially around
very small black holes, where radiation would be thrown out.
"Stephen’s ‘eureka moment' revealed a
profound and unexpected link between gravity and quantum theory: he predicted
that black holes would not be completely black, but would radiate in a
characteristic way," said Martin Rees, astronomer royal, fellow of Trinity
College, emeritus professor of cosmology and astrophysics at the
University of Cambridge and a longtime associate of Professor Hawking.
"Bekenstein’s concept that black holes
had ‘entropy’ was more than just an analogy. This radiation is only
significant for black holes much less massive than stars – and none of these
have been found. However ‘Hawking radiation’ had very deep implications for
mathematical physics – indeed one of the main achievements of string theory has
been to corroborate his idea. It is still the focus of theoretical
interest – a topic of debate and controversy more than 40 years after his
discovery."
Much work has been done to turn that
theoretical interest and exploration into practical observation. But because
black holes are so very difficult to observe and appear in such extreme ways,
it hasn't yet been possible to see the glow of radiation that is expected to
surround them.
That doesn't mean such proof will not ever
be found. Work including CERN's Large Hadron Collider and the discovery of
gravitational waves have shed new light onto black holes, and it's very
possible that Professor Hawking's famous idea will be observed in the coming
years.
Professor Hawking went on to explore the
implications and specifics of his discovery right up until his later years.
They included fascinating insights into how exactly black holes destroyed and
retained information – discoveries that led him to say, for instance,
that black holes
might serve as a passageway into another universe, if you could possibly survive
being hurled into one.
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