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#### Black Holes

Mar. 9, 2013 at 11:34 am

Sorry, I didn't know where to put this thread, so wallah! :).

Can somebody explain black holes to me, as thoroughly yet simply as possible? They've always intrigued me but for some reason I've heard mixed things about them..... Anyways, yeah ^_^

Mar. 9, 2013 at 4:18 pm

The simplest way to put it is that a black hole is essentially a vacuum. It is a region of space time that prevents all form of being from escaping, especially matter and light. There are a lot of theories about black holes, a lot of them involving quantum physics that I couldn't dream of understanding, but no one has ever really had the chance to observe a black hole, because if someone was to get close to one, they would get sucked inside and dragged out until they were only a few atoms wide. Thanks to Einstein and his theory of relativity, we know that gravity does in fact affect the motion of light. A black hole is like a gravitational anomaly, formed by gravitational collapse of a large object, like a star, or high energy collisions. It's very difficult to explain the properties of a black hole without going into some caffeine fueled mathematics... Bare with me here... Black holes have three different independent properties, mass, charge and angular momentum. These properties are important because they can be measured from outside the black hole, they repel similar charges, and once an object comes in contact with a black hole, it is lost to the viewer, best explained in a confusing equation called the Black hole information paradox. It combines quantum mechanics and general relativity to predict that physical information could potentially disappear entirely in a black hole, allowing for many physical states to evolve into the same state. Now it sort of sounds like we're approaching the realm of science fiction. Now that we're past the bare bones explanation for how Black holes are even theoretically possible, there are actually multiple kinds of black holes. The simplest of which is know as a Schwarzschild black hole, which has mass, but neither electric charge or angular momentum. There are also supermassive black holes, stellar black holes, micro black holes, and intermediate mass black holes. If you're actually looking for a more in detail explanation, that makes you brave, and I wish you luck. There is a mathematical solution to stationary black holes known as the Ker-Newman metric, that is used to describe black holes with both charge and angular momentum. Mass in a black hole is an independent ratio, where charge and angular momentum are dependent upon mass. Here is an algebraic equation to solve the charge and angular momentum of a black hole when the mass is known with Planck units with Q as the total electric charge and J as the total angular momentum; Q2+(J/M)2≤M2. I hope I have helped, but I'm pretty sure this has only raised more questions. Isn't science fun?

Mar. 9, 2013 at 4:30 pm

"Isn't science fun?"

>.<

Yes, but Im not good at the understanding part :P

This was helpful, but towards the end I was drooling, so..... Thanks:)

Imaginedangerous replied...
Mar. 9, 2013 at 9:37 pm

You know what density is, right? It's how much stuff you can pack into a single space. A sponge and a block of wood might be the same size, but one of them has a lot more matter crammed into that spot.

A black hole is a point with infinite density- it's matter is packed infinitely tight. It has incredibly strong gravity, strong enough to rip stars and atoms and the very fabric of space and time apart.

They're powerful enough they can even pull in light, which is why they are called black holes- we can't see them. We do know they exist, though, because we can see the things around them getting sucked in.

They're normally formed by big stars collapsing under their own weight, and it's thought that our galaxy roates around a giant one at the center.

Questions? What have you heard about them?

Mar. 9, 2013 at 10:20 pm

That was very helpful... Haha, and yes, I know what density is.

Well, I've heard that people can travel through them (theoretically) and change time periods... But that's sci fi, so scratch that :P and I've heard that at any moment they could engulf the planet... Ya know what, I've just never had the concept fully explained to me so it's all kind of mysterious.

If there's so many black holes in our galaxy, and they're moving around... Why hasn't the entire system collapsed? If the probability of things getting sucked into them is so high, then if one thing is sucked in, doesnt it upset the balance or something? Affect the gravity of our solar system, or .... Something? :)

Jubilex replied...
Mar. 10, 2013 at 12:21 am

I said I'd check this thread out, and yet I can't really add on to what Sorla and Imagine said. They did a good job of explaining :)

As for your questions, I can look up the answers? But I don't know off hand.

Jubilex replied...
Mar. 10, 2013 at 12:26 am

I pulled a copy of Stephen Hawkings "A Brief History of Time" off my book shelf. There's two chapters on Black Holes in there. I really should make the time to read this book. The little snippets that I have read are really informative. Based on what you said about Sorla's post, you may find it a tedious to read, but it also may interest you! At least parts of it.

Mar. 10, 2013 at 4:42 pm

Okay, thanks! You guys have been very helpful :)

Imaginedangerous replied...
Mar. 10, 2013 at 8:20 pm

You can't use a black hole for time travel or any other kind of travel; it would crush you instantly. Einstien theorized that black holes had a negative counterpart called wormholes, which could potentially connect two seperate regions of spacetime. (When you start getting into theoretical physics, you discover that space and time are connected, can be warped, and aren't uniform throughout the universe. It's really bizarre.) Science fiction writers love that concept because it allows for faster-than-light speeds and time travel. The problem is that we have no physical evidence that wormholes actually exist- so far they've only appeared as solutions to complex mathematical equations.

The probability of things getting sucked into black holes isn't actually very high, just because space is so BIG and mostly empty. Yes, black holes are powerful and suck things into them, but they don't often run into things to suck up. Imagine a football stadium. Put a ping pong ball somewhere into the stadium. Now chuck a golf ball at random into the stadium. (The golf ball is a black hole, the ping pong ball is a star.) The two aren't very likely to run into each other.

Black holes are big, but the galaxy is bigger. (The galaxy is different from our solar system. The solar system is just the sun and our closest planets, while the galaxy is a cluster of billions of stars.) A black hole is usually bigger than a solar system- if one approached us then the sun would be slowly torn apart and the earth would get sucked in like a stray Cheerio into a vaccuum. But because the universe as a whole is so big and spread so far apart, black holes aren't likely to come near this one specific star any time soon.

Also, they don't upset the gravitational balance of the universe because they're always getting stronger. Gravity is a property of matter- the more matter you have, the more gravity. That's why the earth has stronger gravity than the moon; it's bigger. Every time a black hole eats something, more matter is crammed into that infinitely dense dot. Thus the black hole grows stronger. The total gravity of the universe doesn't change, it just gets concentrated in that one spot. I'd imagine sometimes this shift of gravity does sometimes cause instability and make galaxies collapse, but again, it doesn't happen very often.

Black holes can be any size. Some are so small they can only consume atoms, and it would take them billions or trillions of years to get big enough to actually consume something visible to the naked eye. I believe there's evidence that particle colliders have created some of these miniature black holes.

Black holes aren't going to consume the Earth, though. If there was one big enough approching, we'd see it coming.

Mar. 10, 2013 at 9:08 pm

^ could we stop it? O.o

Imaginedangerous replied...
Mar. 11, 2013 at 7:28 pm

I doubt it, but we'd know a few hundred (possibly thousand) years in advance. Long enough to evacuate the planet.

Mar. 11, 2013 at 7:41 pm

In theory :). Thanks!

Imaginedangerous replied...
Mar. 12, 2013 at 7:10 pm

Welcome.

Am I the only one who thinks it's funny that this thread ended up right next to the US Congress one? :)

WhoeverIAmThenIAm replied...
Mar. 12, 2013 at 8:52 pm

Lol....weird.

Imaginedangerous replied...
Mar. 13, 2013 at 6:56 pm

Now it's right by North Korea. :)

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