Prof Hawking was a theoretical physicist, cosmologist, and author who was the director of research at the Centre for Theoretical Cosmology at the University of Cambridge before he passed away two years ago. His incredible scientific work included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity and the theoretical prediction that black holes emit radiation, often called Hawking radiation. He was the first to set out a theory of cosmology explained by a union of the general theory of relativity and quantum mechanics, but Prof Hawking was also fascinated by how the world will end, even penning a “near-certain” doomsday date.
And during his ‘Into the Universe’ series he outlined how this could unfold.
He said: “What caused the expansion, or inflation of the universe in the first place?
“When we can answer that, and fully understand the Big Bang, we will also learn the fate of the universe.
“The key to it all is something called dark energy – a mysterious form of energy that pushes space itself apart, even if gravity is pushing space together.
“It seems as if dark energy provided the kick which inflated the universe, although we are not quite sure how.
“What is certain is the fate of the universe depends on how this dark energy behaves.”
Dark energy is causing the rate of expansion of our universe to accelerate over time, rather than to slow down, which challenges theories of a universe that began in a Big Bang.
Prof Hawking explained: “If it slowly weakens, then gravity could get the upper hand and, in 20 billion years or so, the universe would go into reverse and drive everything back to where it came.
“Space itself would contract. This is known as the Big Crunch.
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He added: “I think a Big Chill is what we have in store. Not a Big Crunch.
“So will this be the end of us and life as we know it? Or will we figure out how to navigate to a new universe before then?
“I think we will only know once we truly understand why the universe exists at all.
“Perhaps then, when we finally unravel the whole cosmic puzzle, we will become masters – not just of our own universe, but the universe next door.”