Physics

Stephen Hawking's final paper bursts the multiverse bubble with a Holographic Universe theory

A new theory on the origin of the universe, put forward in the late Stephen Hawking's final research paper, suggests there may not be as many parallel universes in the multiverse as previously thought
A new theory on the origin of the universe, put forward in the late Stephen Hawking's final research paper, suggests there may not be as many parallel universes in the multiverse as previously thought
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Renowned physicist Stephen Hawking passed away earlier this year, and now his final paper, describing a new theory on the origin of the universe, has been published
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Renowned physicist Stephen Hawking passed away earlier this year, and now his final paper, describing a new theory on the origin of the universe, has been published
A new theory on the origin of the universe, put forward in the late Stephen Hawking's final research paper, suggests there may not be as many parallel universes in the multiverse as previously thought
2/2
A new theory on the origin of the universe, put forward in the late Stephen Hawking's final research paper, suggests there may not be as many parallel universes in the multiverse as previously thought

Renowned physicist Stephen Hawking passed away earlier this year, but his legacy to science will live on. His final theory on the origin of the universe has now been published, and it offers an interesting departure from earlier ideas about the nature of the "multiverse."

Ideas about how the universe came to exist the way we see it today have been adapted and built on for decades. The new paper, authored by Hawking and Professor Thomas Hertog, adds to the literature with a new understanding of a theory known as eternal inflation.

After the Big Bang kickstarted the universe, it expanded exponentially for a brief fraction of a fraction of a second. When that inflationary period ended, the universe continued to expand at a much slower rate. But according to the eternal inflation model, quantum fluctuations mean that in some regions of the universe, that rapid inflation never stopped. That results in a gigantic "background" universe full of an infinite number of smaller pocket universes – including the one we live in.

"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 has previously said. "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."

For an idea to be considered scientifically sound, it needs to make predictions that are testable, so experiments can either prove or disprove it. Otherwise, science starts to sound a whole lot like religion – after all, the notion that God created everything in seven days is also elegant and answers all the questions about our existence, but is inherently untestable.

With that in mind, some scientists, including Hawking and Hertog, take that to mean the eternal inflation theory can't be considered without some modification. And that modification is the focus of the new paper.

Renowned physicist Stephen Hawking passed away earlier this year, and now his final paper, describing a new theory on the origin of the universe, has been published
Renowned physicist Stephen Hawking passed away earlier this year, and now his final paper, describing a new theory on the origin of the universe, has been published

"The problem with the usual account of eternal inflation is that it assumes an existing background universe that evolves according to Einstein's theory of general relativity and treats the quantum effects as small fluctuations around this," says Hertog. "However, the dynamics of eternal inflation wipes out the separation between classical and quantum physics. As a consequence, Einstein's theory breaks down in eternal inflation."

Hawking and Hertog's new theory branches off from the holographic principle, which itself is part of string theory. String theory states that each particle in the universe is actually the end point of a one-dimensional string, and the different vibration patterns of each string is what gives a particle its specific properties. Holography, meanwhile, is the idea that the entire universe exists as a hologram, described as 3D spaces that can be mathematically reduced to a 2D projection on a surface.

In their new version of the holographic principle, the authors have wrapped the fourth dimension, time, into the picture. At the beginning of time, eternal inflation can be reduced to a two-dimensional, timeless state on a spatial surface. Doing so allowed them to bypass Einstein's theory of general relativity, which breaks down in previous versions of eternal inflation.

The new theory goes against Hawking's "no boundary" theory, first proposed in 1983. That stated that the universe didn't have what we could understand as a beginning, because the singularity that existed pre-Big Bang had no initial time or space boundaries.

"When we trace the evolution of our universe backwards in time, at some point we arrive at the threshold of eternal inflation, where our familiar notion of time ceases to have any meaning," says Hertog.

As a result, the universe that sprung from the Big Bang in that scenario must be infinite as well, and the pocket universes it contains represent every single possibility.

But according to Hawking and Hertog's new theory of eternal inflation, there was a boundary in the past, so time and space had a beginning. The universe that emerged from that state is also finite, making it far simpler to deal with – and test scientifically. If that turns out to be the case, it deals a blow to the concept of a multiverse containing endless pocket universes.

"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," says Hawking.

So how might this new theory be put to the test? Hertog says the most promising "smoking gun" for the model would be the detection of primordial gravitational waves, ripples through spacetime generated at the beginning of time. These waves would have extremely long wavelengths, meaning existing detectors like LIGO wouldn't be able to pick them up, but Hertog says that LISA, the ESA's planned orbital gravitational wave observatory, could be sensitive enough to detect them when it launches in 2034.

The research was published in the Journal of High Energy Physics.

Source: University of Cambridge

8 comments
Techtwit
Post a comment? You kidding? I'm not going to comment on anything those two guys say, instead will just spend my time trying to understand and digest it. Makes me feel like a sentient brick when I come across minds like theirs.
Douglas Bennett Rogers
How far does the hologram analogue go in the holographic universe? It must just be a lower-dimensional representation that is compared to a hologram, as there isn't a mechanism for making the appropriate real hologram.
BrianK56
Until we are able to travel the cosmos, I don't think there will be a definitive answer only speculation.
Rustin Lee Haase
Multiverses of any flavor. "What a bunch of hippy dippy baloney!" By definition, you can't prove their existence. Is this what our energy research money is funding? I guess university offices are just glorified padded cells. It's sad because smart people often do much better but vanity and egos get in the way.
Bob
I think Douglas Adams had a better grasp on the universe than Hawking or any of his groupies.
apprenticeearthwiz
Has there been any serious examination of whether or not the universe is, in some way, biological, or is our current view that it isn't an unexamined assumption? Accepted wisdom is always temporary.
b@man
So glad we do not have to be exposed to that low density thinker and his stollen concepts anymore:)
RMM
There are some striking aspects of the above that match one particular and very sophisticated and modern Eastern philosophical model that I have been following for the past 45 years. No contradictions with science allowed. Keep going. into the more subtle possibilities. If the principal of Cause and Effect is to stand, then something of an Origin must be that is not the same of the physical and mental effects present in all forms of matter and life. Wave structures provide the link between all that exists and indicate the possibility of a background that has an Infinite Wavelength. I found this article to be really thought provoking. Thanks NewAtlas.
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