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Author Topic: What actually is a Black Hole?  (Read 1976 times)

Offline petrovitch

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What actually is a Black Hole?
« on: 04/12/2009 14:04:09 »
 [O8)] The term black hole is confusing;  [?] why do we not just call them matter to energy converters?  Isn't that what they do?  Is that in fact our real interest in them?  If we could discover how black holes work could we not discover how to develop a perfect form of renewable energy?
« Last Edit: 06/12/2009 08:51:25 by chris »


 

Offline Fozzie

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Re: What actually is a Black Hole?
« Reply #1 on: 04/12/2009 14:19:05 »
[O8)] ...If we could discover how black holes work could we not discover how to develop a perfect form of renewable energy?

See "Large Hadron Collider"
 

Offline LeeE

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Re: What actually is a Black Hole?
« Reply #2 on: 04/12/2009 16:38:44 »
If anything, Black Holes are everything to nothing converters.
 

Offline Mr. Scientist

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What actually is a Black Hole?
« Reply #3 on: 07/12/2009 04:02:40 »
[O8)] The term black hole is confusing;  [?] why do we not just call them matter to energy converters?  Isn't that what they do?  Is that in fact our real interest in them?  If we could discover how black holes work could we not discover how to develop a perfect form of renewable energy?

I'm going to write up a proper sheet on this to explain it in better terms, but here is what black holes are supposed to be about:

Gravity has a strange effect on light. It will couple with light, and bend it around large masses. The idea arose from Einstein, and on the 9th of November in 1919, light was seen to bend around the sun during an eclipse. The times reported on the discovery, 'space would no longer be looked at as extending indefinitely in all directions. Straight lines would not exist in Einstien’s space. They would all be curved and if they traveled far enough they would return to their starting point.'

Finding that our universe was not a Euclidean flat spacetime was indeed a marvel of physics. It showed that space was highly twisted and curved into time, and that gravity itself was a product of these bends in time and space through the presence of matter. It was these types of distortions that led the way for a new prediction in Einstien’s 'theory of relativity.' It predicted a black hole - a whopping gravitational body, unto which nothing can escape its grasp. The center of a black hole has perfect infinite curvature; and it is here that the distortions of space and time become so highly stressed it can actually rip a hole in the fabric of spacetime itself. This is the singularity at the center of the black hole - but it wasn't the same as the singularity of the big bang.

A black hole has this strength because it is a dense concentration of mass. Actually, this mass is so dense, it actually drags space and time around with it, and the curvature it produces is fantastic. For a space shuttle to leave earth's gravitational pull, it needs to have a speed that is strong enough to make the 'escape velocity.' You can imagine the escape velocity is stronger the closer you are to the earth's core. To leave earth, you need a constant speed of something like 25,000 mph.

Now, take the speed of a photon (light) - the fastest particle known. The speed of light is very hard to grasp - saying that it travels 186,000 miles a second isn't always easy to reconcile; just remember, the sun is 15 million km away, and it takes a photon a little over 8.3 minutes to reach us!

Now imagine a massive body in space with such a high concentration of mass, it is actually able to stop light itself - this is a black hole - and this must mean it has an escape velocity of light! A photon, traveling quite happily will be abruptly slowed down until it reached zero-speed. All Luxens (that is particles with a speed of light v=c) and obviously all Bradyons (particles with a velocity under the speed of light v<c) would inexorably be trapped by the intense pull of the black hole... only a hypothetical particle called the 'Tachyon' could escape its pull, quite easily actually. A Tachyon is a particle that moves faster than light v>c.

The idea that an object with a large concentration of dense mass goes right back to the 18th centaury - just after Einstein developed his important relativity theory. It was a physicist Karl Schwarzschild (that is were the black hole gets the name, ‘Schwarzschild radius’ from) who discovered a mathematical solution to the equations of the theory that described such an exotic object. It was only later in the 1930's that theorists Oppenheimer, Volkoff and Snyder took the theory seriously.

Certain stars that cannot support itself against its own gravitational field have a special destiny ahead of them - a star that does this will collapse and form into a black hole. It was John A. Wheeler that coined the term 'black hole' - before that, it had been called 'frozen stars.' Our star, as big as it is, will not collapse until another 5-6 billion years. Altogether, our sun will have lived a total of 11 billion years, and this is quite a good lifespan. Other stars will not be so lucky. They would collapse into a spherical black hole in half that time.

Let's consider a star that is 666,000 times that of the mass of planet earth - this star will have a lifespan of about 5.5 billion years. And there will be much heavier stars out there. You can imagine, stars with a lesser life span with 5.5 billion years as a lifespan would not have given earth enough time to develop life properly; in fact, if science is correct, there wouldn't have been enough time to allow human life to form, considering science informs us that human life did not appear until only about 100,000 years ago, and the earth being 6 billion-odd years old itself. This is another factor that makes human life on earth rather extraordinary.

Physicist Stephen Hawkings, arguably the best mind in the world, has spent much of his time working on the theory of Black Holes. His contribution into the hypothetical black hole is astounding, and if you want more information on his work, i advise you to read his book, 'A Brief History of Time.'

A black hole has something called 'the event horizon' - the event horizon is the spherical surface, or boundary of the black hole. This is the point, that if anything passes it, nothing can escape (apart from a Tachyon mentioned earlier), or unless an object began its journey from the interior; this is because of a strange rule: You cannot pass the surface twice.
It was this reason it was called the event horizon, just like a sunset horizon - you can travel towards it but never quite reach it, or at least, this is what it would be like for an observer sitting comfortably away, watching me traveling towards the black hole... It would seem to take an infinitely long amount of time, and it would look like as if the closer i got to it, the slower i would be in momentum, until it looked as if i had stopped completely. This is because time becomes highly dilated between the traveler and the observer who is a bit away - this is the bizarre effect of relativity. We must take these facts into consideration, when one moves closer to the weird singularity. If our calculations are singular, this means that aspects, like a time interval, or space itself take on infinite values. If this is hard to imagine or a little tedious on the mind - do not fret - anything you don't understand just move on and tackle it later.

If one passed the event horizon, you will inevitably move closer and closer to the singularity in its center, moving faster and faster because space is dragging you closer to the speed of light.

To an observer who is sitting comfortably far away from the event horizon, the hole itself appears static. However, if we moved a little closer to the boundary, it would become visible that the hole itself has a remarkable velocity - in fact, a black hole spins with a velocity of the speed of light. Once inside of the black hole, spacetime are distorted to such a degree, that space and time switch roles. We could not jump into a nonrotating black hole - the force of the black hole would rip matter apart!

So what isa black hole... It's very much like a hole, where nothing can escape apart from things which can travel faster than the speed of light.
 

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What actually is a Black Hole?
« Reply #3 on: 07/12/2009 04:02:40 »

 

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