Did death cheat Stephen Hawking out of a Nobel Prize?

When the iconic physicist died on March 14, 2018, data was already available that could confirm an ominous and far-reaching prediction that he had made more than four decades earlier. Dr. Hawking had postulated that black holes, those jaws of gravitational doom, could only grow larger, never smaller, swallowing information as they progressed and thus threatening our ability to track the history of the universe.

That data was obtained in 2015 when the Laser Interferometer’s Gravitational Wave Observatory, or LIGO, recorded signals from two massive black holes that had collided and created an even more massive black hole.

Dr. Hawking’s prediction was a crucial first step in a series of insights into black holes that have transformed modern physics. What is at stake is whether Einstein’s gravity, which shapes the larger universe, follows the same rules as quantum mechanics, the paradoxical rules that prevail within the atom.

A confirmation from Dr. Hawking’s prediction was published this summer in Physical Review Letters. A team led by Maximiliano Isi, a physicist at the Massachusetts Institute of Technology, and his colleagues had spent years researching the details of LIGO’s results, and in July they finally announced that Dr. Hawking was right, at least in this hole collision. blacks in particular.

“It’s an exciting test because it’s a long-desired result that cannot be achieved in a laboratory on Earth,” said Matthew Giesler, a Cornell University researcher and part of Dr. Isi’s team, said in a email. “This test required studying the merger of two black holes more than a billion light-years apart and it simply could not be accomplished without LIGO and its unprecedented detectors.”

No one claims to know the opinion of the Nobel Prize committee, and the names of the people nominated for the prize will be kept secret for another 50 years. But many scientists agree that Dr. Isi’s confirmation of Dr. Hawking’s prediction could have made Dr. Hawking, and his co-authors in a definitive paper on the matter, eligible for a Nobel Prize.

But the Nobel Prize cannot be awarded posthumously. Dr. Isi’s result came too late.

Nobel Prize week returned on Monday, when certain scientists hope to receive a phone call to anoint them as laureates and summon them to a lavish ceremony in Stockholm on December 20. 10. (This year, due to the pandemic, the prices will be distributed in the countries of origin of the winners).

Dr. Hawking, possibly one of the most celebrated and honored researchers, never won a Nobel and now never will. His story is a reminder of how the award for highest prestige is subject to the fickleness of fate.

## The fool of the universe

The story begins in 1970, when Dr. Hawking was preparing for bed one night, an arduous task for a man who was already half paralyzed by amyotrophic lateral sclerosis or Lou Gehrig’s disease.

He had been thinking about black holes, objects with such strong gravity that not even light can escape from them, according to Albert Einstein’s theory of general relativity. They are portholes to infinity.

Each black hole is surrounded by an event horizon, an invisible bubble that marks the limit of no return; Whatever comes in will never come out. Dr. Hawking realized that Einstein’s theory also meant that the event horizon of a black hole could never decrease. A black hole only gains mass, so the total surface area of its event horizon only grows.

It was a daring idea. Nature didn’t have to work that way. What if black holes could split in two, or splash into each other and disappear, like soap bubbles?

Dr. Hawking’s insight became the cornerstone of a 1973 article. “The four laws of black hole mechanics,“He wrote that with James Bardeen, now at the University of Washington, and Brandon Carter, now at the French National Center for Scientific Research.

These laws also contained a troubling conclusion for physics called the “hairless” theorem. The surface area of an event horizon is a measure of all the information that a black hole ingests. It makes no difference to a black hole whether it consumes matter or antimatter, a Tesla or a Volkswagen, an ostrich or a whale. Black holes have only three properties: mass, spin, and electrical charge. No other details or “hair” are recorded.

This theorem meant that as a black hole aged and its event horizon enlarged, the amount of information lost about what’s inside would also increase. The universe would become more and more foolish, hiding more and more details of its past, including perhaps its existence. The dilemma deepened in 1974 when Dr. Hawking calculated that quantum effects would cause a black hole to slowly leak out and explode.

The quest to understand what happens to information in a black hole has transformed fundamental physics and energized a generation of young theorists. What is at stake is whether Einstein’s gravity, which governs the cosmos, and quantum mechanics, which governs the microcosm, follow the same rules.

“It all started when Hawking realized that the total horizon area of black holes can never go down,” Dr. Isi said.

But with no black holes to experiment with, Dr. Hawking’s ideas could not be tested.

## LIGO to the rescue

LIGO would change that. This was the promise that Kip Thorne, a theoretical physicist at the California Institute of Technology and one of the founders of LIGO, made to Dr. Hawking in 2003. The new matrix could classify the properties of black holes by the time Dr. Hawking turned 70 in 2012.

“Your gift is that our gravitational wave detectors – LIGO, GEO, Virgo and LISA – will test your predictions of Golden Age black holes, and they will begin to do so long before you turn 70,” said Dr. Thorne. he remembered telling her recently.

It took LIGO longer than that, until September 14, 2015, to observe its first historical event: two colliding black holes. By matching the wave patterns detected with computer simulations, the LIGO team concluded that one of the black holes was 36 times more massive than our sun and the other 29 times more massive, which equates to 65 suns in total. The collision resulted in a new black hole with a mass of about 62 suns. Three suns of energy had disappeared in the gravitational waves that shook the universe.

The observation confirmed not only the existence of gravitational waves, as Einstein had predicted 100 years earlier, but provided the first direct evidence for black holes.

A leaked copy of the discovery document reached Dr. Hawking a few days before the official announcement of the findings. He began to find no mention of the four laws of black hole mechanics, or of the possibility that the discovery could put them to the test. He spoke to Dr. Thorne, the author of the article, on Skype.

“Steven is quite surprised,” said Dr. Thorne wrote to his colleagues.

It had never occurred to anyone to check the laws of black hole mechanics, and it was too late to add anything to the article. Also, as Dr. Thorne recently explained, the data was too noisy to measure the size of the newly formed black hole well enough to confirm that Dr. Hawking’s Theory.

In 2017, Dr. Giesler, then a graduate student at Caltech, and his colleagues used numerical simulations of colliding black holes to take a deeper look at the doomsday whirlpool.

When a newly fused black hole forms, it vibrates. Like a drum, it generates a fundamental tone, as well as harmonics: overtones or undertones. The nuances turned out to be surprisingly strong early in the fusion process, Dr. Giesler said he found. Using these nuances, in 2019 he and his colleagues proved the “hairless” theorem, which states that black holes can only be described by three parameters.

This summer they were able to expand their analysis by exploiting a nuance of the new black hole to measure its size. They concluded that the area of the new black hole’s event horizon had increased, as Dr. Hawking had predicted so long ago.

## Nobel dreams

Would this have won Dr. Hawking the Nobel Prize if he were still alive?

“I’m not comfortable speculating,” said Dr. Thorne, who shared the 2017 Nobel Prize in Physics for his involvement in the development of LIGO.

Harvard’s Andrew Strominger, a longtime collaborator of Dr. Hawking, said: “I am not aware of the Nobel committee’s deliberations, but Hawking might already have been included in this award if he was still alive. Certainly these more recent experiments would further strengthen the case. “

Daniel Holz, an astrophysicist at the University of Chicago who is part of the LIGO collaboration but not Dr. Isi’s team called the result “incredibly cool.”

“You could say it’s an observational confirmation of one of their predictions,” he said. “I hope the Nobel committee realizes this.”

The physics prize has always leaned toward practical and experimental discoveries; even Einstein won the award for explaining the photoelectric effect, not relativity. The furthest the Nobel committee has gone in theoretical astrophysics lately was in 2020, when Roger Penrose of the University of Oxford received the award for showing that black holes were possible in the universe.

But he shared the award with two astronomers, Reinhard genzel, from the Max Planck Institute for Extraterrestrial Physics, and Andrea Ghez, from the University of California, Los Angeles, who had studied the supermassive black hole at the center of the Milky Way.

Even if Dr. Hawking was still alive when his black hole area theorem was proved, it would have been difficult to fit it in: a Nobel Prize can be awarded to up to three people. And what about Dr. Bardeen and Dr. Carter, Dr. Hawking’s co-authors? And Dr. Isi’s team?

Dr. Hawking would not be the first scientist to die too soon for a possible Nobel Prize.

“I have been told that the Nobel committee regretted not awarding a prize to Hubble,” wrote Michael Turner, a prominent cosmologist who now works for the Kavli Foundation in Los Angeles, in an email, referring to astronomer Edwin Hubble, who discovered the expansion. of the universe. “But he died first.”

Robert Brout, a theoretical physicist at the Université Libre de Bruxelles, would likely have been included in the 2013 Nobel Prize for predicting the existence of the Higgs boson, along with his colleague François Englert and Peter Higgs from the University of Edinburgh, if he had not. done. died in 2011.

Ronald Drever of the University of Glasgow, one of the founders of LIGO, might as well have shared the 2017 Nobel with Dr. Thorne and Rainer Weiss of MIT had he not died in early 2017. His position was filled by Barry C. Barish from Caltech.

Dr. Hawking rests with Isaac Newton and Charles Darwin at Westminster Abbey. Maybe that’s better than spending a winter in Stockholm.