Black holes aren't the cosmic vacuum cleaners they are rumored to be, but could you still fall into one? What would happen to you? The answer to that question depends on whom you ask (thanks to quantum gravity).
Black holes are regions of space where the gravity is so thick that not even light can force its way out. As we discussed in a previous episode, black holes can form as a result of stellar death. Once a star runs out of fuel to burn, and thus can no longer support itself via radiation pressure, the layers of metals fused up to that point will all come crashing down towards the center. The stellar core can then implode in the production of a supernova or, as is the case for more massive stars, collapse to then form a black hole.
If massless photons cannot escape the clutches of a black hole, then certainly neither could we. But what would happen to you if you were to find yourself falling into a black hole? Thanks to Einstein’s theory of general relativity, a framework that helps us understand how space and time behave in the presence of strong gravity, we can predict the specifics of what would happen to us without having to go through it ourselves.
The answer is surprising because you get a different one depending on whom you ask. You, as the faller, would experience a reality very different from what I, as an observer from the outside, would see. So, if we can’t agree, what do we think happens to you?
Black Holes Don’t Suck
First, let’s clear up a common misconception. Black holes get a bad reputation for sucking in their surroundings, like some sort of cosmic vacuum cleaner. In reality, the gravitational pull of a black hole is the same of that for a regular star—just a lot stronger.
So astronomical objects can easily stay in orbit around a black hole, just as we stay in orbit around our Sun, so long as they are moving fast enough to balance the black hole’s gravitational pull. In fact, the hundreds of billions of stars in our galaxy orbit a central, super massive black hole with a mass of 4.6 million times that of our Sun crammed into a space of less than ~100 million miles (about the distance between the Earth and the Sun).
If we were to get knocked off course by a particularly large collision (think galaxy scales here, not just a tap from an asteroid), we could in theory be sent careening towards our galaxy’s central black hole and pass the point of no escape. However, this would require a pretty significant event and so we have much more likely things to worry about (like what happens to our Sun when it runs out of fuel).
You'll Very Quickly Resemble Spaghetti
For smaller black holes, like those formed from collapsed stars, the gradient in the gravitational pull is so steep (i.e. the force of gravity changes rapidly as you move closer) that you would not get anywhere close to the perimeter of the black hole. The gravitational pull on your feet would be so much stronger than that on your head that you would be pulled apart like string cheese pretty quickly.
However, around a larger black hole, you would have more time to approach before being torn in two. In fact, given a large enough black hole, you’d have all the time in the universe …