Stephen Hawking’s final paper grapples with the nature of a multiverse

STEPHEN Hawking’s final message to the world has been revealed in a stunning new theory — and it rethinks our place in the universe.

IN HIS final paper published after his death, Professor Stephen Hawking grappled with one the most fascinating ideas in cosmology and theoretical physics — proposing a new reality for our universe, and perhaps others like it.

Along with Thomas Hertog, a professor of theoretical physics at Belgium’s KU Leuven University, the research was published this week in the journal High Energy Physics.

The paper, titled ‘A Smooth Exit from Eternal Inflation?’ explores the notion of alternative universes — an idea known as the multiverse — and what we might be able to do to prove their existence and nature.

The University of Cambridge, where Professor Hawking worked, announced the publication on Wednesday and if nothing else, it’s certainly true to form. In other words, don’t expect an easy read.

Professor Hawking’s most famous book, A Brief History of Time was renowned for being difficult to understand — and that was about as layman as the famous physicist got.

The latest paper uses a mix of string theory and complex maths problems that resemble hieroglyphics to arrive at his theory on the multiverse.

SO WHAT IS A MULTIVERSE?

Scientists believe our universe sprang into existence with the Big Bang, followed by an unimaginably rapid expansion known as inflation. Within our observable universe, inflation ended long ago.

But some ideas of inflation say it never stops, persisting in other regions of the cosmos forever. This eternal inflation produces a “multiverse,” a collection of pocket universes of which our own universe is just one.

Theoretical physicist Dr Brian Greene describes the idea of a multiverse like a “cosmic bubble bath” where each bubble represents a separate universe. Earth is just a planet, inside a galaxy, inside a single bubble floating in that bathtub.

These universes could have different features, different properties, different kinds of particles, different structures.

READ MORE: The beautiful mystery of string theory

The multiverse hypothesis arises from cosmology and quantum physics.

Researchers have successfully worked on the possibility of receiving an observational signature from another universe (if they even exist) but the idea of actually travelling to one is well beyond the realm of current scientific reality.

HAWKING’S TAKE ON THE MULTIVERSE

The final Stephen Hawking research paper explores the idea that our Big Bang wasn’t the only one of its kind and discusses how a space probe could possibly find such evidence.

But he came to the multiverse somewhat reluctantly. According to his co-author, Professor Hawking was never a big fan of the multiverse theory but he knew it was hard to avoid.

“Pretty much any reasonable model of the Big Bang which we could come up with led us to a multiverse,” Professor Hertog told CBC in March. “If anything is possible — if a multiverse is too gigantic, too wild — then our theory won’t say anything about our own universe, and so it’s useless as a scientific theory.”

The pair ultimately set out to find a more simple, less chaotic theory that explained the multiverse. Well, simpler if you understand theoretical physics, anyway. It remains incomprehensible for the rest of us.

Professor Stephen Hawking Physics at Cambridge University in 1988. Picture: Brian Randle/Mirrorpix

Essentially Professor Hawking’s paper suggests that there may be a much smaller range of possibilities for universe types than previous estimates have posited.

If there are indeed an infinite number of these pocket universes and they’re all different in some way, then how typical is our own universe and what does that mean for the observations we make about the fundamental realities of nature?

These are the questions that plague the idea of a multiverse and Professor Hawking wanted to propose a multiverse theory that maintained the usefulness of our own universe and, more importantly, the observations we make about it.

Physics professor David Kaiser of the Massachusetts Institute of Technology told the Associated Press that the paper argues that “the behaviour of our own, observable universe might not be a rare outlier, but perhaps (be) relatively typical”.

However, with all theories and ideas in this particular domain “this is all rather speculative,” he added.

Professor Hawking on the other hand, before he passed away in March, seemed more confident in the idea that underpins the research.

“We are not down to a single, unique universe, but our findings imply a significant reduction of the multiverse, to a much smaller range of possible universes,” Professor Hawking said, according to a Cambridge University press release.

— With AP