The final paper penned by the late theoretical physicist Stephen Hawking has been published, revealing a unique new perspective on the so-called multiverse and our own local patch of the cosmos.
And, it could upend everything we think we know about the events before and after the Big Bang.
Borrowing points from the string theory – the concept that the universe is a complex hologram – Hawking and colleague Thomas Hertog argue that our universe and other ‘pocket universes’ are not the infinite fractal structures some have proposed.
Instead, Hawking says the universe is ‘reasonably smooth and globally finite,’ setting new boundaries in cosmological history that could ultimately allow the theory to be tested.
The new model challenges earlier theories proposed by Hawking himself, and could help to finally explain the universe in areas where Einstein’s theory ‘breaks down.’
‘The usual theory of eternal inflation predicts that globally our universe is like an infinite fractal, with a mosaic of different pocket universes, separated by an inflating ocean,’ Hawking said in an interview a few months before his death.
‘The local laws of physics and chemistry can differ from one pocket universe to another, which together would form a multiverse.
‘But I have never been a fan of the multiverse. If the scale of different universes in the multiverse is large or infinite the theory can’t be tested.’
The inability to test the infinite multiverse theory, Professor Hertog explains, also means it does very little to predict the behaviour of our own universe.
In the new paper, published to the Journal of High Energy Physics, the physicists argue that the eternal inflation scenario is wrong.
The new model cuts the structure of the universe down to a ‘more manageable, smaller, smoother universe,’ Hertog said.
While it doesn’t do away with the concept of multiple universes entirely, it trims them down to finite entities.
‘We predict that our universe, on the largest scales, is reasonably smooth and globally finite,’ Hawking said.
‘So it is not a fractal structure.’
Doing this could help to bridge the gap between classical and quantum physics, as, according to Professor Hertog, ‘Einstein’s theory breaks down in eternal inflation.’
The researchers pull from the string theory concept of holography, which argues that 3D reality – including time and space – can be projected on a 2D surface.
‘Our new theory is based on a technique which we have borrowed from string theory, and that seems to imply a much more manageable, global structure of the universe in which regions can differ from each other, but not at all as much as in the old theory,’ says Hertog, a professor at KU Leuven in Belgium.
‘I think the key point about our model is not so much that constant density surfaces in the universe are finite, but rather that the variation in the multiverse is restricted.
‘In other words, that the range of different pocket universes is much smaller. That makes the cosmology based on our new theory a lot more predictive, a lot stronger as a scientific theory.
‘And therefore, ultimately we hope, testable.’
By this model, it is essential to examine our own reality as a part of the vast, global cosmology and its history, the physicist explains.
‘We are not just somehow outside the system and looking at it – no we are part of reality,’ Hertog says.
‘This is very different from other scientific dissonance. It’s a very subtle point, with a lot of debate about it. And it’s extremely difficult to implement if the multiverse is truly infinite.’
According to Hawking and Hertog, the new model will allow for the concepts on the nature of the universe to be tested in a way that earlier theories did not.
And, the key to investigating it lies in gravitational waves that go far beyond those generated by black hole mergers.
Daily Mail
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