Why are black holes so alluring?
You could cite plenty of reasons: They’re matter-gobbling monsters, making them the perfect plot device for a Disney movie. They warp spacetime, demonstrating the weirdest implications of general relativity. They’re so massive that inside a boundary known as the event horizon, nothing — not even light — can escape its gravitational grip.
But perhaps the most intriguing feature of black holes is their sheer mystery. Because of the rules of relativity, no one can report what happens inside the boundaries of a black hole.
“We could experience all the crazy stuff that’s going on inside a black hole, but we’d never be able to tell anybody,” radio astronomer Heino Falcke told me. “We want to know what’s going on there, but we can’t.”
Falcke and his colleagues in the international Event Horizon Telescope project lifted the veil just a bit two years ago when they released the first picture ever taken of a supermassive black hole’s shadow. But the enduring mystery is a major theme in Falcke’s new book about the EHT quest, “Light in the Darkness: Black Holes, the Universe, and Us” — and in the latest installment of the Fiction Science podcast, which focuses on the intersection of fact and science fiction.
Falcke, who’s an astrophysics professor at Radboud University in the Netherlands, is well-placed to provide an inside look at the troubles and triumphs that the Event Horizon Telescope’s team encountered on the way to their breakthrough image in 2019.
Starting 20 years ago, Falcke pushed for the idea of combining data from radio telescopes around the world to generate pictures of the black holes that lie at the heart of galaxies, including our own Milky Way. Once the idea took off, he became the chair of the project’s science council — and helped direct hundreds of astronomers as they made observations, shipped back the data from eight sites around the globe, and developed algorithms to generate the imagery.
Falcke and his teammates encountered plenty of earthly challenges:
- Because the project relied upon precisely synchronized radio observations in locales ranging from Hawaii and Spain to Chile and Antarctica, astronomers had to wait for when the weather is good enough at every site. For that, it turns out that April is the kindest month. “For none of the telescopes, it’s the best time of the year — but it’s the least worst for all of them,” Falcke explained.
- Hundreds of trillions of bytes of data were collected on each day of an observing campaign, and getting all that precious data back on hard drives took as long as six months. In Antarctica, for example, the southern winter ruled out any shipments until October.
- The team had to deal with social as well as technical breakdowns. In Mexico, one researcher ended up being detained by a gun-toting squad during the 2018 observing campaign. “We still don’t know whether it was the secret police or some gang … there was a little battle going on at the time,” Falcke said. “But that was a pretty scary experience.” Because of that and other setbacks, including the coronavirus pandemic, the first campaign in 2017 has been the most productive to date, producing the M87 black hole image.
The good news is that the Event Horizon Telescope team was able to resume observations this April. “We tried again, and it probably worked,” Falcke said. “We don’t know yet, because we haven’t looked at the data.”
Coming attractions could include a picture of the black hole at the center of the Milky Way, known as Sagittarius A*.
The black hole’s shadow should have about the same angular size as M87’s black hole, but the observation is tougher to make because the radio telescopes have to look through all the material swirling between our vantage point and the galactic center.
What’s more, the fact that Sagittarius A* is 1,000 times closer and smaller than M87 actually makes it harder to get an stable image. “We’re working on it, and we’ll be publishing the data on it,” Falcke said. “It’s not going to be lost data — that, I can promise.”
Falcke said the Event Horizon Telescope has been looking at other black holes as well. “Some actually look quite interesting, and one will come out [in a research paper] in a couple of weeks,” he said. “But there we will not be able to see the event horizon, because they are too small or too far away.”
The team aims to build up imagery over time that could show black holes in motion. “I’m convinced, with our experiment, we’ll be able to make movies,” Falcke said. “That’s one of the next goals that we have. We may need a few more telescopes, and in the end, we actually want to go to space.”
Black holes and the Event Horizon Telescope are also at center stage on video streaming services like Netflix and Apple TV+, thanks to the release of a 98-minute documentary titled “Black Holes: The Edge of All We Know.” The film weaves the EHT’s story in with other threads, including efforts to simulate black hole behavior in the lab, and the quest to resolve what’s known as the black-hole information paradox.
The information paradox goes back decades, and involves one of the world’s best-known physicists, Stephen Hawking. He and other theorists held a strong belief that information, like energy, cannot be created or destroyed. However, once an object plunges beyond a black hole’s event horizon, all of the information about that object is seemingly lost forever. Or is it really?
Hawking went back and forth about strategies for solving the puzzle. “Black Holes: The Edge of All We Know” tracks Hawking and his collaborators as they try to show that the information falling into a black hole can somehow end up being imprinted on its surface.
The tragedy of the team’s quest is that Hawking died in 2018 before the work could be completed. Nevertheless, his name appears on the published paper, titled “Black Hole Entropy and Soft Hair.”
“It would have made him so happy to realize that we’d got somewhere with this project,” Sasha Haco, the paper’s lead author, says in the documentary. “And unfortunately, we just didn’t get there in time.”
Death and the end of time also figure in Falcke’s musings on the mystery of black holes, in the book and in the documentary. “People always make the link intuitively to death,” he says in the film.
Like death, as described metaphorically in William Shakespeare’s “Hamlet,” a black hole is an undiscovered country from whose bourn no traveler returns. “Black holes represent the end of space and time, as the Big Bang really represents the beginning of space and time,” Falcke told me. “This universe will go in some direction that you’ll never be able to know where it’s heading at some point.”
As a scientist, Falcke could see that as a source of frustration. But as a Christian, he sees that as an opening for things that lie beyond the event horizon, beyond the realm of physics.
“There are some things, I think, in our lives and our universe that you’d be only able to address and give a place to via faith — or just not think about it at all,” he said.
Physics may have pushed Stephen Hawking toward atheism, but the mysteries of black holes are pulling Falcke deeper into his faith.
“We’re not able to explain everything as physics alone,” Falcke insisted. “You know, the universe is so much richer that there’s still a place, if not a need, for hope, love and faith. That’s really what makes us human, to search for answers, to look for the beyond, to understand what we can know and what we cannot know.”
Cosmic Log Used Book Club
By some counts, there have been more than two dozen movies and TV shows that make use of black holes as plot devices. As far as Falcke is concerned, the gargantuan black hole in the movie “Interstellar” comes closest to reality. But even though the filmmakers relied on visualizations from Nobel-winning physicist Kip Thorne, Falcke said the movie’s black hole still misses the mark on a couple of key features.
“What really made me cringe in the movie is when they were going tward the black hole, and then they were hit by all these rocks and dust, right?” he said. “If you go into this black hole, all this stuff moves with the speed of light. You can’t see the rocks coming towards you. They would have such an enormous energy, just a little rock would just completely obliterate you. And it wouldn’t stay rock; it would become extremely hot and gaseous.”
Falcke also said the black hole in “Interstellar” didn’t have the jets of hot plasma that should be shooting out along the rotation axis.
“If you ever fall into a black hole, that’s your hope, right?” he said. “Try to catch one of these magnetic field lines and fly with it out into interstellar space. That’s a wonderful accelerator.”
Despite its shortcomings, the fact that “Interstellar” leads Falcke’s list of black hole movies is enough justification to designate the movie and Kip Thorne’s spin-off book, “The Science of Interstellar,” as this month’s selection for the Cosmic Log Used Book Club. For 19 years, the CLUB Club has highlighted books (and yes, movies, too) with cosmic themes that have been around long enough to turn up at your local library or secondhand shop.
Black holes are such a massive topic that one book isn’t nearly enough. So in addition to “Light in the Darkness” and “The Science of ‘Interstellar,'” I’ll toss four more books into the maelstrom:
- Death by Black Hole, and Other Cosmic Quandaries: Neil deGrasse Tyson explains why spaghettification is something black hole travelers need to worry about (although I’d put a black hole’s blazing-hot accretion disk higher on the list of hazards).
- The Little Book of Black Holes: Physicists Steven S. Gubser and Frans Pretorius dig into the nuts and bolts of black holes and relativity. The authors keep references to formulas at a minimum, but this book isn’t for the scientifically faint of heart.
- Black Hole Blues and Other Songs of Outer Space: Janna Levin (who makes an appearance in “Black Holes: The Edge of All We Know”) tells the story behind the first-ever detection of gravitational waves from the merger of two black holes.
- Icarus at the Edge of Time: In a picture book suitable for the pre-teen set, theoretical physicist Brian Greene updates the ancient myth of Icarus to reflect the weirdness of spacetime around the edge of a black hole.
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