Ethan Kwan
March 11, 2021
Black holes are the weirdest things ever. What are they, where do they come from, what happens if you fall into one, and will they die?
Formation
Stars are basically big balls of hot hydrogen and helium that collapsed a long time ago from gas clouds because of their immense gravity. The cores are so hot, that the core fuses hydrogen into helium, releasing a tremendous amount of energy. This energy pushes the outer layers outward, as the outer layers try to gravitationally crush the core. As long as there is fusion in the core, the star remains stable.
Unfortunately for the star, it has a limited amount of hydrogen. Once it runs out, the star needs to get fuel, but it doesn’t have enough heat to fuse helium. So, the outer layers win, and the star’s core starts to get smaller. This makes it hotter, and now it has enough energy to fuse helium! Now, it fuses helium into carbon, and the whole cycle repeats. Helium releases LESS energy than hydrogen, but it’s enough.
Eventually, the star runs out of helium, so what does it do? That’s right, it fuses the carbon, again releasing LESS energy than helium. And then it fuses neon, then oxygen. If this was a sun sized star, this is where it will stop. If the star is heavier, it will continue fusing heavier and heavier elements, releasing less and less energy at a time, until the star hits iron.
Iron (unfortunately for the star) cannot be fused. Iron builds up at the centre of the star, until it reaches a critical amount, and the radiation-gravity balance is broken.
The core collapses. Atoms don’t want to be near each other, but the collapsing star’s pressure is enough to fuse the electrons and protons into neutrons, which then get squeezed as tightly as an atomic nucleus, and an iron ball the size of the Earth gets squeezed into the size of a city. The whole star collapses onto the core and within a fraction of a second, the star implodes, moving at about a quarter of the speed of light, feeding even MORE mass into the core. This collapse is where all the heavier elements are created, such as uranium and gold, as the star dies in a supernova explosion! The core of this supernova turns into a neutron star, or if it’s massive enough, a black hole.
Black Holes
If you looked at a black hole, you would really be seeing the event horizon, which is the point of no return. Anything in the event horizon needs to be travelling faster than the speed of light to escape, which is not possible. Sorry1! So that’s why we see a black sphere, reflecting nothing. Well, if that’s the “black” part, where is the “hole” part?
That would be the singularity. We’re not sure what it is, because math and physics (and common sense) breaks down at that point. It is a single point in space, with infinite density and zero volume or surface area. We just don’t know. It’s kind of like dividing by zero.
Note that black holes do NOT suck up things like a vacuum cleaner. If we swap the sun with an equally massive black hole, nothing will change, except for the fact that Earth would freeze to death.
What if you fall into a black hole? There are two possible scenarios.
- You die a quick death.
The black hole curves space so much, that if you were going down head first, the force on your head is way stronger than the force on your feet, and you get stretched apart like a piece of spaghetti. The name for this is my favourite name for ANY phenomenon in science… “Spaghettification.” - You die a very quick death2.
Right after you cross the event horizon, you meet a firewall and will be terminated instantly.
Neither of these options are particularly pleasant.
How soon you would die depends on the mass of the black hole. If it’s a small one, it would kill you even before you entered the event horizon. For a slightly larger black hole, you could travel inside it for a while.
Black holes come in different sizes. There are the stellar ones, with a few times the man of the sun, and about the size of an asteroid. Then there are the supermassive ones that sit at the centres of galaxies.
Currently, the largest black hole known is called TON 618, which is 66 million masses of the sun. It’s 390 billion km in diameter, making it 65 times the distance from the sun to Pluto!
However, these behemoths won’t last forever. They can slowly evaporate through a process called Hawking radiation.
Hawking Radiation
To understand hawking radiation, we need to know about empty space. Empty space isn’t really empty, but it’s full of particles constantly being created and annihilating each other. When this happens at the edge of a black hole, one particle gets sucked in, and one escapes, becoming a real particle. So, the black hole is slowly losing energy. This happens incredibly slowly at first, and speeds up as the black hole gets smaller. When it arrives at the mass of a large asteroid, it’s radiating at room temperature. When it is the size of a mountain, it’s radiating at over 6000 degrees! And in the last second of its life, it radiates with the power of a billion nuclear bombs.
But this process is incredibly slow. The largest black holes will take up to a googol years to evaporate! A googol is 10100, which is a long time3.
Black holes are probably the weirdest things in the universe. So I hope this article has helped you learn more about these things!
1Blame Einstein.
2I think I prefer option 1.
3[Citation needed]
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