The Many Universes of Stephen Hawking | Paul – NewsBreak Original

Stephen Hawking, Credit: Ida Lee

"Shortly after my 21st birthday, I went into hospital for tests. They took a muscle sample from my arm, stuck electrodes into me, and injected some radio-opaque fluid into my spine, and watched it going up and down with X-rays as they tilted the bed. I was diagnosed as having ALS...or motor neuron disease, as it is also known. The doctors could offer no cure and gave me two and a half years to live". (Stephen Hawking. "A Brief History of Time" 1991 film, https://youtu.be/EyHl4l7oRds?t=118).

The previous words from English cosmologist Stephen Hawking (1942 - 2018) don't come close to a complete description of his struggle to be trapped in his own body as his condition gradually paralyzed him and was only able to communicate with movements of his cheeks and the help of a computer to create sentences (https://science.howstuffworks.com/dictionary/famous-scientists/physicists/stephen-hawking5.htm#:~:text=How%20did%20Stephen%20Hawking%20talk,on%20running%20lists%20of%20words.).

Thankfully, his mind wasn't affected and he was free to ponder about the cosmos.

Hawking had the choice between two major fields of study, particle physics and cosmology. Hawking chose cosmology ("A Brief History of Time" 1991 film). The way he saw it in those days, particle physics was mostly a field to categorize subatomic particles into different families as zoology or botany would do with organisms. Still, cosmology rested on more solid theoretical ground, such as Albert Einstein's general relativity and the theory of Black Holes (collapsed large stars) developed by the father of the atomic bomb, Robert Oppenheimer. Hawking's "research on general relativity had concentrated mainly on the question of whether or not there had been a big bang singularity" (A Brief History Of Time, chapter 7. Stephen Hawking. Bantam Books. 1996).

In other words, did the universe have a beginning from a single point?

A singularity is defined as a point where the laws of physics break down and space-time loses its meaning due to infinite gravity. Not even light can escape this point of incredible force and infinite density. One type of singularity may be interpreted as a Black Hole (a collapsed large star), as theorized by the British mathematician and Nobel laureate Roger Penrose (born in 1931) and another interpretation of a singularity may be applied to the universe itself, "at the time of the Big Bang (i.e. the initial state of the Universe)" as theorized by Stephen Hawking (What Is A Singularity?. From Universe Today.). Their understanding of singularities was "merged together to be known as the PenroseHawking Singularity Theorems". So both inside a black hole and also at the beginning of the universe, there is a point where infinity rules.

A Black Hole drawing, Credit: Ida Lee

According to Hawking's theorem, there was a beginning in time in an extremely small point-like region of space. The universe began as a singularity. This is the major theme of the 2004 biopic "Hawking", starring Benedict Cumberbatch. The film presents the proof that the Big Bang is the origin of the universe as opposed to cosmologist Fred Hoyle's proposal of an eternal universe with no beginning and no end. It was Fred Hoyle who coined the term "Big Bang" to let others know the absurdity that the universe began at an extremely hot and dense point (Sir Fred Hoyle; Coined 'Big Bang'. Los Angeles Times. latimes.com) and it was Stephen Hawking who established "the existence of cosmological singularities such as the big bang" (Singularity Theorems, https://www.personal.soton.ac.uk/dij/GR-Explorer/singularities/singtheorems.htm).

In 1983, Professor Hawking revised his theory about the universe in collaboration with physicist James Hartle (born in 1939) (James Hartle. In Wikipedia). In this newer version of the universe, there is no boundary, that is, the universe had no point in time that we can describe as an absolute beginning. As an analogy, using the Earth's surface, when you reach the South Pole, "there is nothing south of the South Pole". The South pole is just an ordinary point on the surface of the Earth; it has no privileged position. In the same way, if you go back in time to the moment of the Big Bang, this point isn't special either, it is just an ordinary point of pure space, and time "doesn't exist". Again, "once you trace back the universe to its beginning, the concept of time (as we define it, at least) becomes obsolete" (How Stephen Hawking Worked. HowStuffWorks. By Marianne Spoon. https://science.howstuffworks.com/dictionary/famous-scientists/physicists/stephen-hawking3.htm).

Professor Hawking combined two fields of physics to be able to understand this timeless state of the universe in its primeval stage; he combined quantum physics and Einstein's general relativity to understand better the Big Bang (Ashutosh Jogalekar. Oppenheimers folly: On black holes, fundamental laws and pure and applied science. In Scientific American. https://blogs.scientificamerican.com/). The universe was so small that time separated from space (no space-time continuum), there was no temporal beginning (no boundary), and it was a quantum point of pure concentrated space.

Hawking, as well as Einstein before him, wondered if God had a choice when he created the universe. It seems that God didn't have a choice because "if the no-boundary proposal is correct, (God) had no freedom at all to choose initial conditions" because the universe's beginning is meaningless. He would only be able to choose the laws of the universe in its later evolution (A Brief History Of Time. Stephen Hawking).

However, this universe without a beginning doesn't mean that the universe has existed forever. In simple words, it means that there was no time before the Big Bang. The universe and time itself were created around 14 billion years ago.

"There are innumerable universes besides this one, and although they are unlimitedly large, they move about like atoms in You..." (From the Bhagavata Purana)

In the Hertog-Hawking proposal ("Stephen Hawking's last paper" in collaboration with the Belgian cosmologist Thomas Hertog), they theorize that the multiverse has fewer universes than the traditional conception of a multiverse. Hawking predicts that our universe is finite and a "dead end" when it comes to reproducing other universes, just as other universes may have also stopped inflating, thus reducing the infinite number of universes. Not all universes reproduce, otherwise their theory "can't be properly tested" in an infinite multiverse.

Also, the Hertog-Hawking's multiverse can be "observationally testable" if we consider gravitational waves produced by the interaction of our universe with other universes of the multiverse during inflation right after the big bang. Hopefully, these waves might be detected in the future with space observatories keeping in mind that astronomy has been enhanced with the solid confirmation of gravitational waves in 2015 (From Ku Leuven News, https://nieuws.kuleuven.be/en/content/2018/new-cosmological-theory).

Thomas Hertog explains that if we go back in time, "we arrive at the threshold of eternal inflation where our notion of time ceases to have any meaning" and "Einstein's theory breaks down...". As a consequence, instead of using General Relativity to explain the early universe, Hawking and Hertog use string theory to describe our universe as a hologram where the dimension of time is projected out of eternal inflation. In other words, time emerged from "a timeless state on a spatial surface at the beginning of the Universe" (Stephen Hawking's Final Theory About Our Universe Has Just Been Published, And It Will Melt Your Brain by Michelle Starr, https://www.sciencealert.com/stephen-hawking-s-last-physics-paper-theory-on-eternal-inflation-multiverses).

Our universe that evolves in time has a boundary after all: Eternity. There is no beginning because our beginning is insignificant if we consider that we are part of a larger multiverse.

As American cosmologist Alan Guth puts it: "In the picture of eternal inflation...our Big Bang was actually just one event in a larger picture, it was not really the beginning of anything in the absolute sense".

On the left, the universe began in a singularity. On the right, the universe didn't have an absolute beginning.Credit: Ida Lee

Do you prefer the singularity-universe which had a beginning in time in an infinite point of density?

Or the no-boundary universe which had no beginning because time didn't exist before the Big Bang?

How about the multiverse where eternity is our universe's boundary, Einstein's relativity theory breaks down and our notion of time is a hologram?

Which of the three do you prefer?

Roger Penrose was awarded half of the 2020 Nobel prize in Physics (https://www.nobelprize.org/prizes/physics/2020/summary/). The other half wasn't awarded to Hawking. He had passed away in 2018 and the theme of the prize was Black Holes, not Universes.

Hawking also worked on the Black Hole theory, but the Nobel prize isn't awarded posthumously. However, Hawking won many other prestigious awards recognizing his work in cosmology.

"It was wonderful to float weightless free of my wheelchair" (Stephen Hawking, from StarTalk with Neil deGrasse Tyson and Stephen Hawking describing his experience on a zero-gravity flight in 2007, https://youtu.be/TwaIQy0VQso?t=767)

How many more universes would Hawking have created if he had lived longer? I wonder, what is the correct connection between quantum theory and relativity? I wonder how a universe evolves in a timeless state? I wonder if an empty universe has no conscious observers then how...? I wonder if the fate of our universe will be a Big Crunch or a Big Rip or... I wonder if my mind may also float free. I wonder...

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The Many Universes of Stephen Hawking | Paul - NewsBreak Original