It’s a question that has plagued humanity since we first learned about black holes just over a century ago: What the hell would it be like to plunge past the point of no return?
We don’t have an answer yet, but a new supercomputer simulation is the best guess we have, based on the current data.
“People often ask about this, and simulating these hard-to-imagine processes helps me connect the mathematics of relativity to actual consequences in the real universe,” says astrophysicist Jeremy Schnittman of NASA’s Goddard Space Flight Center.
“So I simulated two different scenarios, one where a camera — a stand-in for a brave astronaut — just skips the event horizon and goes back, and one where it crosses the border, sealing its fate.”
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The unknown is like a flame to the moth of our curiosity, and black holes could be the poster child for the unknowable. Formed from the cores of massive dead stars collapsing under their own gravity, they are so dense that their matter is compressed into a space that is currently indescribable to physics.
One result of this compression, however, is an event horizon; a roughly spherical boundary where the pull of gravity is so strong that even the speed of light is not sufficient to achieve escape velocity.
This means that there is no way of knowing what lies beyond the event horizon. Light is the main tool we use to explore the universe. If we don’t see light from a black hole, we just… can’t tell what’s there.
Even in theory, we face paradoxes where information is both preserved in the event horizon from the perspective of an observer and locked away forever from the perspective of an object crossing the boundary.
What we do know, however, based on the way light and matter travel around black holes, is that the gravitational regime around the event horizon is just absolute bananas. In some cases, anything that dares get too close is pulled to atoms by the sheer force of the forces involved. The exact point at which this happens depends on the mass of the black hole involved – star mass, or up to about 100 suns in mass; or supermassive, millions to billions of solar masses.
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“If you have a choice, you want to end up in a supermassive black hole,” says Schnittmann.
“Stellar-mass black holes, which contain up to about 30 solar masses, have much smaller event horizons and stronger tidal forces that can tear apart approaching objects before they reach the horizon.”
Amazing breakthroughs in recent years have given us a wealth of data about the space around black holes. The supermassive black holes M87* and Sagittarius A*, at the centers of galaxies M87 and our own, respectively, have been the subject of spectacular direct imaging campaigns. The black hole itself is still invisible, of course, but the light emitted by the exciting, glowing clouds of material around each black hole has given us unprecedented insight into the gravitational environment.
Schnittmann, who has created several black hole simulations for NASA, based his new one on a supermassive black hole very similar to Sagittarius A*. He started with a black hole with a mass equivalent to about 4.3 million suns, and along with data scientist Brian Powell, also of Goddard, fed their data into NASA’s Discover supercomputer.
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After running for five days, the program has generated 10 terabytes of data, which scientists have used to create several videos about what it might feel like to fall into a supermassive black hole. On a typical laptop, this would take 10 years.
The simulated camera starts about 640 million kilometers (400 million miles) from the black hole and moves inward. As it gets closer, the disk of material around the black hole and the inner structure known as the photon ring become clearer.
These elements and space-time become more distorted the closer the camera gets. Finally, the flyby completes almost two laps of the black hole before plunging beyond the event horizon and reforming after just 12.8 seconds.
In the other version, the camera approaches the black hole before escaping the gravitational pull and flying away.
It would be nice to think that at some point we can learn more about the environment beyond the event horizon. In the meantime, we can enjoy a taste of the wacky space-time antics that would exist around its perimeter – all from the safety of our own home planet.
