Death by Black Hole
As of lately, it seems that everybody is trying to tell you when and how the world will end. Some scenarios are far more familiar and likely than others. Those that are widely discussed in the media range from infectious diseases to nuclear war, all the way to collisions with massive asteroids. While they are all vastly different from one another, they all share one thing in common: they're all able to effectively end the human species once and for all.
But all of these scenarios fall short when compared to one thing: black holes. We're all familiar with them, but what exactly is a black hole? Black holes are regions of space where the gravity is so high that the fabric of space and time has curved back on itself, taking the exit doors with it. But what does that even mean, and why are black holes black?
Well, any large object, such as a black hole, star, or planet, has a certain escape velocity that is needed to escape the pull of gravity on that object. For example, Earth's escape velocity is about 11 kilometers per second. Move that fast, and you could escape Earth's pull and fly off to the edge of the universe. But chances are, you'll probably be pulled in by something's gravity eventually. But that's not the point. The stronger the gravity an object has, the higher the escape velocity is.
Now, black holes have some of the highest gravitational pulls in the entire universe. In fact, black holes are theorized to have singularities, where gravity pulls you with infinite force. But we'll get to that later. Let's say somehow we made a black hole with the same exact mass of Earth, about 6 times 10 to the 24 kilograms. All right, this looks good, except this isn't to scale. It would look something more like this.
In order to turn Earth into a black hole, you'd have to crush it down to about the width of your pinky finger, about 9 millimeters. So, these two massive objects have the same exact mass, except one is the size of your finger and the other is the size of a planet. So, how does this happen? When black holes are created, they are typically formed by the death of massive stars, those worth about 20 to 30 times the mass of our Sun.
While living stars undergo nuclear fusion in their choosing, they combine lighter elements such as hydrogen and helium. This fusion of elements creates energy and pressure that pushes out away from the Sun, while gravity keeps the star held together. But as time goes on, over billions of years, stars begin to run out of these lighter elements and move on to heavier ones. They begin to fuse together denser elements such as carbon and oxygen, all the way up to silicon and iron.
Except here lies the problem: iron can't fuse with anything. There isn't any more energy being produced, so the power of the star's gravity takes over, collapsing the star under its own weight until it explodes in what we call a supernova. The outer parts of the star fly hundreds of thousands of miles into space, while the core continues to collapse under its own weight and becomes densely compressed.
Remember how Earth has an escape velocity of about 11 kilometers per second? Well, after all that, the core of what was the star is still massive enough—about two and a half times the mass of our Sun—and dense enough that the escape velocity of the core becomes much greater than the speed of light, over 300,000 km/s. This forms what we know as a black hole: an area of space is created where nothing, not even the fastest thing in the universe, light, can escape.
But let's have some fun with it and dive into one. Imagine just for a moment that you are aboard a spaceship, but not any normal spaceship, one that can defy physics, one that could accelerate you to any extremely high velocity, even higher than the speed of light. This is completely impossible, but it's okay because you know your spaceship can reach any speed imaginable. You have no fear of black holes and decide to fall into one in the quest of science. You choose the supermassive black hole at the center of the Milky Way galaxy, Sagittarius A*.
This behemoth of a black hole is over 88 million kilometers wide, nearly 100 times as wide as our own Sun...