Of all the places in the universe you could go, a black hole is probably one of the last places you actually want to be. Even if you know very little about a black hole, you must think that perhaps it’s not one of those bucket list destinations. In truth, there are many reasons you’d want to avoid a black hole, but if you want to know explicitly what would happen if you ran afoul of one, why don’t we take a look and see?
What is a Black Hole?
In very simple terms, a black hole is a place in space where the force of gravity has become so intense that nothing is able to escape from it, including light itself. That’s why we call it black, because there’s no physical way to see it because light can’t get away from it. Without light, there is nothing to see.
There are two kinds of black holes that could exist in our universe. The first are primordial black holes. It’s believed that these might have been formed shortly after the Big Bang. They would be less dense than the other kind of black hole, called a stellar black hole.
A primordial black hole would have formed before stars even existed. It’s been theorized that there could have been dense patches of matter in the early universe, just when things were very hot and just getting going. They could have collapsed under their own gravity forming a smaller version of what we think of as a black hole today.
The more common version of a black hole is a stellar black hole, formed inside of a star. When a star gets too massive at the end of its life cycle, if it is big enough, and by that we mean about 25 times the size of our sun, it will collapse in on itself, becoming so dense that a black hole is formed.
There are also supermassive black holes in the universe which, as you can guess by the name, are pretty dramatic. Supermassive black holes sometimes exist in the center of galaxies. It’s theorized that these reformed when large stars collapsed billions of years ago and the black hole has been able to draw in matter like other stars ever since, growing larger and larger as a result. It’s possible that they could have even swallowed other black holes.
How Many Are There?
Basically, nothing is going to escape from a black hole; you don’t have the torque to motor away from something that even light can’t get away from. That means they would be pretty dangerous. Surely, they can’t be that common, right? They’re like sharks in the ocean, just something you have to keep an eye out for. Well, that’s harder to get a feel for.
For some time the most reasonable answer to the question of how many black holes there are in the universe was a lot. Too many to count. No way to estimate. That’s because detecting cosmic phenomena is difficult at the best of times given the size of the universe. Trying to detect things that can’t actually be seen is somewhat harder. You need to measure gravitational waves and observable phenomena usually associated with stars. It’s like counting rocks in a pond based on splashes in some ways.
Of course, any number we do come up with is going to be an estimate, we’re not giving precise numbers here. And watch the same way as we estimate the population of the Earth without literally counting every person out there. But we’ve made progress in the last few years and we do have a number for how many black holes we think might exist. Are you ready? You might want to sit down, take a look over your shoulder, make sure nothing is about to pull you into oblivion.
Working with a lot of complex data, astrophysicists have estimated there are roughly 40 quintillion black holes in the universe. A quintillion has 18 zeros, if you weren’t sure.
How Big Do They Get?
At the center of our galaxy, the Milky Way galaxy, there is a black hole known as Sagittarius A. This is not the largest black hole that we have discovered. However, it is 4 million times the size of our sun to give you a little perspective.
A typical stellar black hole could be a few times the size of our sun to as much as a few hundred times the size of our sun. Keep in mind, that that’s when they first form. Like any baby, it’s going to grow bigger. As a stellar black hole begins to feed, as it draws in all the gases and particles from the system around it, it might start taking in other stars as well and just get bigger and bigger. The older it gets, the larger it will get.
Sagittarius A, as we mentioned, is 4 million times the size of our sun. You’ll be happy to know that it’s a small one. There’s a galaxy called Holmberg 15A that also has a black hole in its center. That one is 40 billion times the size of our sun.
Supermassive black holes like the one in Holmberg 15A may date back to the first billion years of our universe. It’s likely they have swallowed a few stars in their lifetime and it’s also possible that they are the result of two galaxies colliding and one black hole consuming another black hole. They may also be accumulating dark matter.
A fun contrast here is the primordial black hole that we discussed earlier. These black holes are much less dense than stellar black holes and supermassive black holes. While it’s just a theory, it’s believed that some of these could have a mass 100,000 times less than a paperclip. So we’re talking about a pretty tiny, unimpressive cosmic phenomenon in terms of its size. On the other hand, they could be 100,000 times more dense than our sun, so they’re probably still not worth encountering.
What Happens in a Black Hole?
Do you like spaghetti? It’s pretty tasty, you have to admit. And of all the pasta shapes, it’s one of the better ones. It lends itself nicely to eating, just curling it around your fork or slurping it up in an uncouth manner. It’s fun! Unless the spaghetti is you.
Spaghettification is the unusually fun name given to the process of what happens to something that falls into a black hole of the right mass. The gravity of the hole would essentially funnel you, like spaghetti, towards it. If you’ve ever tried to force yourself into the shape of spaghetti in the past, you realize it can’t be done comfortably. This is going to kill you pretty dead.
Even in something as small as a space shuttle, the gravitational forces at the bow of the shift will be intensely stronger than those aft. This is the result of the steep gravitational gradient you experience as you get closer to the black hole. So try to imagine a bowl of Jello and you’re using a straw to suck up the middle, top part.
The bottom of the bowl won’t be affected at all yet but you are going to lay waste to whatever the straw is touching. That is what happens to your ship. It all gets funneled into that straw whether it was meant to fit in there or not. The tidal forces of the black hole will stretch you and then tear you apart. That’s spaghettification.
One thing to remember is that spaghettification can’t happen in every black hole. It’s very much dependent on the mass of the black hole itself. Supermassive black holes have so much gravitational pull that this gradient won’t affect you at all. Not that it would be a pleasant experience, you would just fall into it and experience all the other terrible things that happen.
On the upside, which is not an upside at all, you would probably die well before that happened. There’s something called an accretion disk around a black hole which is where all the bits of matter that haven’t been pulled in yet accumulate. It’s like a cosmic bathtub ring, just all the goop around the center.
The problem with the accretion ring is that it’s susceptible to the friction of the gravitational force of the black hole itself. It becomes so hot, in fact, that it releases radiation. Gravity and friction work together to create X-rays and gamma radiation. So, before the black hole itself reduces you to cosmic spaghetti, the accretion disk is going to burn you to an absolute crisp.
But that’s not all! Because of the time dilation effects of a black hole, as you approach that event horizon, to most of the rest of the universe you are going to look like you’re slowing down. In fact, you may stop altogether and freeze right there, relative to the rest of the universe, potentially forever. We have to ignore the spaghettification and radiation to get to this point. But, as has been said, if you enter the event horizon, you will never leave.
So What is The Event Horizon?
The term “Event Horizon” is a bit daunting to wrap your head around. It sounds like something big, right? It has the word “event” right there. And “horizon” is something you see in the distance. So this sounds like some big, monumental thing that is far away. What it really refers to is just the border of the black hole. Consider it a wall that isn’t physical. It is the part that separates the black hole from space around it.
The thing that makes the event horizon of a black hole such a significant part of the black hole is that it’s the point of no return. It’s also technically what allows us to see a black hole. Because light can’t escape past the event horizon, we have to look at the edge of the event horizon to even know a black hole is there. That’s where all the gases, space dust, unlucky UFOs, and assorted other things will accumulate and become super heated before they cross that border. It’s like a cosmic whirlpool, and has been referred to as a halo because it’s visible around an impossible darkness that no earthly instruments can actually see.
Can Anything Ever Escape a Black Hole?
With a gravitational force so strong that light can’t even escape it, it seems a reasonable and safe assumption that there is nothing in all of creation that can escape a black hole unless it’s able to travel faster than light. Physics tells us that’s not really a thing, except sometimes, in theory. But there are some things that can withstand the gravitational force of a black hole: subatomic particles.
Black holes emit jets of plasma that’s full of positrons and electrons. They get shot from the black hole itself back towards the event horizon at close to the speed of light. They bounce around violently and are ejected out of the event horizon again, back into space. But how the heck does that happen?
The working theory is that the black hole draws in all of these particles, some of which are negative energy particles. The comparison here was to a negative calorie food. Something you eat that actually takes more calories to digest than you’ll get from digesting it. So the black hole fills itself with these negative energy particles that actually draw power from the black hole, reducing its overall force around them and accelerating the particles themselves. By being in the black hole, they get charged up while the black hole loses power.
So, while most things will never escape, there are limited circumstances when particles can. As for you and me? No such luck.