Black holes are seen as the most frightening beings in the universe. They’re always lurking out there somewhere, but they’re nearly impossible to spot.
First theorized to exist by Albert Einstein and eventually discovered by Stephen Hawking, black holes have such immense density and gravity that not even light can escape from them. For a long time they remained mostly a mystery to science, but now we are starting to understand exactly what they are and how they work in terms of physics.
Astrophysicist and science communicator Dr. According to Becky Smethurst, black holes are neither black nor holes. Smethurst is also the author of A Brief History of Black Holes: And why nearly everything you know about them is wrong.
“They look more like mountains of matter than holes,” Smethurst tells Newsweek. “It’s not just the black hole itself, because they’re prisons of light, and you can’t get any light from the black hole. But you can get light from the region around the black hole.”
“You have material that spins inward, reaches enormous speeds, heats up like iron in a forge and starts to glow. Not only does it start to glow in optical light, it also emits X-ray light, UV light, and you also get some radio emission from it. So they light up like Christmas trees.”
Around black holes is an irreversible boundary of all matter and energy, defined as the event horizon. Once you cross this limit, it is impossible to escape the black hole’s gravity. Beyond the event horizon, there is finally the singularity, a single point almost impossible to even imagine where the immense mass of the black hole resides.
What happens if you fall into a black hole?
If you somehow fell into a black hole, what we might describe as “spaghettiization” happens to your body on the journey between these places. Spaghetti basically means that the gravity on your feet will be stronger than on your head, and you will stretch like spaghetti as you get closer and closer to the black hole. This is a pretty scary scenario. What you experience and witness as someone falling into a black hole will be very different from what a bystander safely away from the event horizon would see.
Smethurst said, “As you approach the event horizon, you see the black hole getting bigger and bigger. Black holes make these weird twists of light, making them appear larger than they appear. When you fall beyond the event horizon, all the light of the universe will strike your eye for a brief moment. And beyond that “We never know what you’re going to see – we don’t know if it’s incredibly bright, completely dark, or if there’s another form of matter that we can’t see. Because right now, according to our understanding of the laws of physics, we have no idea what’s beyond the event horizon.”
However, your friend who sees you falling into a black hole encounters a completely different image.
“Let’s say you have a small beacon on your spaceship, like a little lighthouse that flashes every 30 seconds. The light signals from that will take longer and longer to reach you between each flash because of the gravitational force, essentially as the light slows down as you get closer to the black hole,” says Smethurst. “So the [observer] can never see you cross that event horizon. You seem frozen in space and time forever.”
However, the time between crossing the event horizon and becoming spaghetti may not be as short as you might expect. Depending on the size of the black hole, the distance between the event horizon and the singularity can be very large. TON 618, the largest black hole we’ve ever discovered, is 40 times larger than the distance from Neptune to the Sun.
“There’s a possibility that someone falling into this black hole and traveling down this gravitational gradient could live their entire human life traveling [inside the black hole] in relative safety. But it’s interesting to see how the concept of time will change: As soon as it crosses the event horizon, any direction in space is the same,” Smethurst said. “It will come in time. There is no such thing as the past because you can never go out.”
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