WV25115 said:
Can someone explain, in nice simple language, the concept of black holes?
The simple answer is: No. Black holes cannot really be explained in very nice simple language. They require a lot of understanding of basic physical concepts. I would suggest that you start with a course in college level physics, and then proceed to a course in modern physics and of course astronomy.
I've been trying to figure this out, but can't grasp what exactly they are, what happens to time and space and matter in one, etc. I don't have a scientific mind, so please keep that in mind as well.
Thank you!
OK. I'll try to add somethings here. Black holes are theoretical constructs of Einstein's General Theory of Relativity. We are pretty sure such things exist, but it still is a matter of some debate. Einstein in 1916 first explained his General Theory of Relativity (which basically expanded on the ideas he had presented in his special theory of relativity in 1905). In that paper he explained how light could be bent by gravity. How so? Because gravity bends space and time itself. This has been proven many times, but the first time was in 1919 when observations of an eclipse showed that indeed the light from stars passing close to the sun was indeed bent by the exact amount Einstein had predicted. The observation won Einstein instant acclaim and notoriety around the world. It probably prompted the Nobel Prize committee to award him the Nobel prize in physics, although he got that technically for his explanation of the photoelectric effect and not relativity.
In any event, it is a simple matter to show then that if gravity can bend light, and the stronger the gravitational field the more light is bent, then obviously if the field is strong enough then the light will get bent back on itself. Since according to Einstein's Special Theory of Relativity nothing can go faster than the speed of light, then nothing would be able to escape once it got back into a black hole. All that is required is that a mass be compressed small enough so that its gravitational field would be so concentrated in such a small region so as not to allow light to pass through.
So what happens? Nobody really knows. There be dragons in the center of a black hole and scientists are still really trying to figure it out. It will depend on whether String Theory turns out to be a correct model and a few other things.
But there is so much more. Black holes aren't really "black" - sure they don't allow any escape by photons, but they do in fact give off quite important signatures that we can detect - mostly due to infalling matter. Most of our candidates for black holes, like Cygnus X-1 (an x-ray source in the constellation of cygnus) are binary systems, where one part is a star which is being cannibalized by a dense companion. X-ray emissions from infalling matter indicate that such systems could be potentially black holes - depending on the way in which the x-rays "flicker." Also, the center of most galaxies are considered black hole candidates.
But if you were to look at a black hole you would see something odd. Take a companion and throw him into the black hole - what would you see as he waves good bye? Well, first he would appear to slow down and turn redder. In fact you would never really seem him fall into the black hole. He would just appear to get slower and slower and redder and redder. Confusing? I told you it wasn't possible to explain it simply. But it makes sense if you think about it carefully. The light coming from your friend is being stretched out by the gravitational field of the black hole. Eventually the black hole radius (actually the radius of what is called the "Event Horizon" (or point of no return)), will grow slightly enough to swallow your friend.
But of course there's still lots more. For example, Black holes actually will evaporate over time. This is due to quantum effects occuring as light and matter are sucked into a black hole. This is also one of the great achievements of Stephen Hawking.
OK, enough for now. Go read the following books: "A Brief History of Time" and "The Universe in a Nutshell" both by Stephen Hawking. They are great introductory books that will get you started on a fantastic journey of discovery and learning which hopefully you will never complete!
SLD
pretty interesting stuff. and yes walking with christ your explanation was pretty accurate, i couldn't have explained any better myself
