Stephen Hawking died on March 14. His work was admired by many, as he largely contributed to the concept of the universe as we know it today. However, before he died, he had been working on a scientific paper that sheds light on the origin and behavior of the universe. Many media outlets were praising it, saying that Stephen Hawking’s last paper could be the most important research he ever did. So what’s inside his last paper?
Hawking worked in collaboration with a theoretical physicist from the Institute for Theoretical Physics at the University of Leuven in Belgium, Thomas Hertog. They produced a paper titled “A Smooth Exit from Eternal Inflation.” Although currently it’s under a review by an undisclosed science journal, it’s available at the arXiv. It was initially submitted on July 24, 2017. However, it went through a revision on March 4, 2018.
It’s normal that Stephen Hawking’s last paper is getting a lot of attention given that the scientist worked on it only days before he died. The Sunday Times reported that his last paper could be the most scientific legacy. According to The Telegraph, several researchers said that if the evidence had been found before the famous scientist died, “it may have secured the Nobel Prize which had eluded him for so long.”
According to some physicists, the universe will always be expanding, according to the theory dubbed eternal inflation. According to Gizmodo, cosmologists Alan Guth and Andrei Linde speculated that “in the multiverse that results from eternal inflation, anything can happen will happen an infinite number of times.”
“Inflation is a stage of exponentially fast expansion of the universe, which makes the universe very large and uniform. Long time ago, it was realized that in some parts of the universe inflation may continue forever,” Linde told Gizmodo. “As a result of this process, which I called eternal inflation, the universe may split into many exponentially large parts with different properties; the universe becomes a multiverse.”
Avi Loeb from Harvard Astronomy Department told Gizmodo that the new paper worked on by Hawking and Hertog makes predictions on the type of universes that can exist in the so-called multiverse, using mathematical formulas.
“This requires making use of the quantum language to describe everything, including all possible types of universes that are born in the multiverse,” Loeb told Gizmodo. “They conjecture—but not prove—that only a limited set of possible universes are allowed. Anthropic reasoning should apply only to a restricted subset of all possibilities.”
If there are more universes inside the multiverse, like theorized, there could be some different constant compared to those that we know, or even more or less dimensions. In Stephen Hawking’s last paper, they are trying to get through the mathematical infinity to prove that there are more universes that can exist and be observed. The scientists said that it could be possible to notice the evidence of the multiverse by observing the background radiation of the universe, although that hasn’t been proven yet.
“It’s heavy on speculative assumptions, and I don’t see any concrete predictions,” Frank Wilczek, a theoretical physicist at MIT and Nobel laureate told Gizmodo. “Very hard to understand, though, at least for me, and I may be missing something.”
According to Linde, understanding the processes that are going on behind eternal inflation are challenging to understand. Scientists would need to research quantum fluctuations on a large scale. However, Hawking and Hertog’s new paper exactly looks into this issue.