The Nobel Prize in Physics was awarded to three astrophysicists Tuesday for work that was literally out of the world, and indeed the universe. They are Roger Penrose, an Englishman, Reinhard Genzel, a German, and Andrea Ghez, an American. They were recognized for their work on the gateways to eternity known as black holes, massive objects that swallow light and everything else forever that falls in their unsparing maws.
Dr. Penrose, a mathematician at Oxford University, was awarded half of the approximately $1.1 million prize for proving that black holes must exist if Albert Einstein’s theory of gravity, known as general relativity, is right.
The second half was split between Dr. Genzel and Dr. Ghez for their relentless and decades long investigation of the dark monster here in the center of our own galaxy, gathering evidence to convict it of being a supermassive black hole.
“I’m so thrilled” she said in an email.
The Nobel Assembly announced the prize at the Royal Swedish Academy of Sciences in Stockholm.
More Einstein, Less Math
Black holes were one of the first and most extreme predictions of Einstein’s General Theory of Relativity, first announced in November 1915. The theory explains the force we call gravity, as objects try to follow a straight line through a universe whose geometry is warped by matter and energy. As a result, planets as well as light beams follow curving paths, like balls going around a roulette wheel.
Einstein was taken aback a few months later when Karl Schwarzschild, a German astronomer, pointed out that the equations contained an apocalyptic prediction: In effect, cramming too much matter and energy inside too small a space would cause space-time to collapse into a point of infinite density called a singularity. In that place — if you could call it a place — neither Einstein’s equations nor any other physical law made sense.
Einstein could not fault the math, but he figured that in real life, nature would find a way to avoid such a calamity.
In 1965, however, a decade after Einstein’s death, Dr. Penrose slammed the door on Einstein’s hopes.
Born in 1931 into an intellectual family, Dr. Penrose is a professor at the University of Oxford. Dr. Penrose recalled in an interview recently that when he was young and the family took walks in the country, they would play chess in their heads, keeping track of various moves without a physical board.
“My job was the runner,” he said, “I would take the moves from one brother and race up to my father. And I just got exercise by running back and forth.”
A talented mathematician, he invented a new way of portraying space-time, called a Penrose diagram, which bypassed most of the mathematical complexities of general relativity.
His diagrams are now the lingua franca of cosmology. He proved that if too much mass accumulated in too small a place, collapse into a black hole was inevitable. At the boundary of a black hole, called the event horizon, you would have to go faster than the speed of light — the acknowledged cosmic speed limit — to get away. So you could never escape. Inside the boundary, time and space would switch roles and so all directions would lead downward, to the center, where the density became infinite and the laws of physics, as we knew them, would break down.
He showed that the black hole would become a gateway to the end of time, the end of the universe.
He is also famous for discovering Penrose tiles, a way of tiling an infinite floor without ever repeating the pattern. He has also published iconoclastic views of artificial intelligence and the origins of consciousness in books like “The Emperor’s New Mind: Concerning Computers, Minds and the Laws of Physics.”
As they hailed the news, some astronomers and physicists lamented the absence of Stephen Hawking, the Cambridge University cosmologist who was arguably the world’s leading black hole theorist until he died in 2018, making him ineligible for the Nobel.
Shortly after Dr. Penrose made his breakthrough calculations, Dr. Hawking and Dr. Penrose collaborated using the same methods to prove that if general relativity was right, the universe must also have had a beginning — a fairly big discovery.
John Preskill, a Caltech physicist, celebrated the accomplishment of Dr. Ghez and the other scientists in a tweet. But he added that the moment was poignant.
“I’m thinking of how much Stephen Hawking would have enjoyed sharing a Prize for advances in General Relativity,” he said.
The Monster of the Milky Way
Today, astronomers agree that the universe is speckled with such dark monsters, including beasts lurking in the hearts of most galaxies that are millions and billions of times as massive as the sun. They’ve even taken a picture of one in a galaxy some 55 million light-years away.
But closer to home, at the center of our Milky Way galaxy, 26,000 light-years from here, there is a faint source of radio noise called Sagittarius A*. In 1971 Martin Rees and Donald Lynden-Bell suggested that it was a supermassive black hole.
Working independently, Dr. Genzel and Dr. Ghez, and their teams, have spent the last decades tracking stars and dust clouds whizzing around the center of our galaxy with telescopes in Chile and Hawaii, trying to see if that dark dusty realm does indeed harbor a black hole.
Dr. Ghez was born in New York on June 16, 1965. She is a professor at the University of California, Los Angeles and one of the authors of the children’s book “You Can Be a Woman Astronomer.” Noting on Tuesday that she was only the fourth woman to win the physics prize, she said that she hoped to inspire young women.
“It’s a field that has so many pleasures, and if you’re passionate about the science, there is so much that can be done,” she said.
Dr. Genzel is a director at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, and a professor at the University of California, Berkeley.
He grew up in Freiburg, Germany, a small city in the Black Forest. As a young man, he was one of the best javelin throwers in Germany, even training with the national team for the 1972 Munich Olympics.
Dr. Genzel and Dr. Ghez have shared other honors for their work, including the Crafoord Prize in 2012, often referred to as the astronomy Nobel.
Over the years, their observations have crept closer to the conclusion that whatever is at the galactic center is dark and must have a mass equivalent to four million suns, in order to exert enough gravitational pull to keep the stars and gas that circle it in check.
One of the stars, which Dr. Genzel calls S2 and Dr. Ghez calls S0-2, is a young blue star that follows a very elongated orbit and passes within just 11 billion miles, or 17 light-hours, of the mouth of the putative black hole every 16 years.
During these fraught passages, the star, yanked around an egg-shaped orbit at speeds of up to 5,000 miles per second, should experience the full strangeness of the universe, according to Einstein. That last happened in the summer of 2018, with both teams watching for deviation or surprise from the star.
To conduct that experiment, astronomers needed to know the star’s orbit to a high precision, which in turn required decades of observations with the most powerful telescopes on Earth.
“You need 20 years of data just to get a seat at this table,” said Dr. Ghez, who joined the fray in 1995.
In fall 2018, Dr. Genzel announced that they had detected the gas clouds circling the center of the galaxy every 45 minutes or so at 30 percent the speed of light. Those clouds are so close to the suspected black hole that if they were any closer, they would fall in, according to classical Einsteinian physics, Dr. Genzel said.
The results provide “strong support” that the dark thing in Sagittarius “is indeed a massive black hole,” Dr. Genzel’s group wrote in the journal Astronomy & Astrophysics in 2018.
“Their pioneering work has given us the most convincing evidence yet of a supermassive black hole at the centre of the Milky Way,” the Swedish Academy of Sciences said in its announcement.
Einstein might grumble, but he would also be proud.
Knowing that black holes exist, physicists say, only reminds us that we don’t understand what goes on inside them and that we don’t really understand gravity.
The black hole “teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as ‘sacred,’ as immutable, are anything but,” said John Wheeler, one of the leaders of general relativity as a professor at Princeton and the University of Texas at Austin, in his 1998 autobiography.
Most physicists believe that Einstein’s theory of general relativity will need to be modified to cope with extreme situations such as the Big Bang or whatever does happen in black holes.
“We already know Einstein’s theory of gravity is fraying around the edges,” Dr. Ghez said in an interview a couple of years ago. “What better places to look for discrepancies in it than a supermassive black hole?”
Tuesday’s award extends a recent streak of prizes for astrophysics.
Last year, the cosmologist James Peebles split the prize with two astronomers, Michel Mayor and Didier Queloz, for work the Nobel judges said “transformed our ideas about the cosmos.”
And in 2017 the committee honored Rainer Weiss, Kip Thorne and Barry Barish for the discovery of gravitational waves from black holes.
“Astrophysics seems to own the Nobel Physics Prize these days,” said Michael Turner, a cosmologist now at the Kavli Foundation, adding ”and rightly so with all that we are learning about the Universe.”