If a black hole is black, and space is black, how can anyone see it?
Wow! You tried to be clever! Too bad you're way off. That makes being clever kind of ironic, doesn't it? Sorry, I apologize. It was too hard to resist. Your question is a good one, and I'll try to give a good answer.
First of all, space isn't really black. Maybe to us it is, but that's because we only see a portion of the light spectrum. "Black" space is chock full of all kinds of stuff: light from suns and whatnot, x-rays, hard radiation, and my personal favorite, virtual particles.
Like me after drinking, energy needs to be carried
Quantum mechanics tells us that in order for any energy to move from one point to another, it has to be passed along by force particles. These are tiny things, smaller than atoms, that carry the four forces of nature: gravity, electromagnetism (which includes light), weak nuclear, and strong nuclear. If this is confusing, don't worry. I'm just setting the scene.
If space was truly empty, then no energy could cross it. That means we wouldn't see anything up there. But we do. Therefore, space must be full of something.
So scientists came up with an idea that must have been born out of mild drug use: what if space is full of particles and anti-particles that are constantly appearing out of nowhere, smashing into each other, and destroying each other almost instantly? This would give energy something to "walk" across but it would still be kind of empty. Neat-o!
You mean I gotta prove my theories? Oh man.
Nice theory, if not a bit weird, but it's hard to prove. If these particles appear and disappear that quick, how could you find them? Enter the real subject of this article, the black hole. See, black holes have what's called an event horizon. This isn't a real thing, just a boundary where, if you go past it, you're toast. Stay on the other side of the line, and you can get away. Cross the line and you can never escape the black hole's gravity. That sucks.
Ever heard of Stephen Hawking? He wondered what would happen if those particle/antiparticle thingies happened real close to that event horizon. If one particle stayed on the safe side of the event horizon, and the other crossed the horizon, then there's no cancelling each other out.
One gets sucked into black hole hell, while the other goes shooting across space. Since these particle/antiparticle thingies are supposed to happen all the time, it would look like the black hole was shooting all these particles all over the place.
To quote Mr. Hawking, "Black holes ain't that black." They more or less emit radiation, which we can look for. And we've found it. It's now called Hawking Radiation, and it proves that particle/antiparticle thingies do occur and that black holes are around.
For those who found the above stupid
Not satisfied? Just to make up for teasing you in the beginning, here's two other ways to detect black holes. Stuff doesn't just fly directly into the hole. Like in a sink, stuff spirals around the hole before eventually disappearing. This is called the accretion disc because junk piles up in a big disc around the hole. Spinning fast creates heat, and the disc emits x-rays.
Also, all this spinning creates one wicked magnetic field. This field pulls some of that junk and shoots it up and down along the black hole's verticle axis.
So there's three ways to find black holes in black space. Neither are really black, but we don't have to go there again. Right?
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