Black Holes are probably my favorite thing in the Universe to learn about. The idea that a natural thing can take all the laws of physics and completely disregard them facinates me. We have never accually seen a black hole yet we can observe them by detecting x-rays which are shot out of black holes. Almost everything we know about black holes is entirely theoretical, although we do believe that what we know is true.

First, the creation of a black hole. A black hole starts out as a star much like anyother except that it has to have a mass greater than 2.2 SM's (solar mass). A star is held together by two forces, and probably many other insignificat forces. Anyway, these two forces are the Strong Nuclear Force which acts outwards from its center, and Gravity which acts inwards towards the center. These two forces act equally keeping the star in equilibrium. When a star dies usually the SNF wins and the star expands rapidly in a huge explosion known as a supernova. These are some of the brightest objects in the sky. In the case of a black hole, the star expands, then slingshots back as gravity becomes stronger than the SNF. When this happens the star collapses in on itself. Most of these become Neutron stars which are extremely dense dead stars. With a black hole the star collapses so much that the entire mass of the star occupies a single point in space, smaller then the point on a needle. This is what creates a black hole.

Now, to know what a black hole is you have to know about spacetime. The concept of spacetime was first thought of by Georg Bernhard Riemann in 1854. He felt that Euclidean (greek) Geometry was too rigid to explain space for it was imposible to have curves in it. Because of this he invented a new geometry called Riemann Geometry. He created a geometry based on curved space rather than flat that used ten numbers to describe any point in space. This idea of four dimensional space (x,y,z,time) revolutionized physics and eventually evolved to become Einsein's general relativity. So, spacetime is all around us and a part of us. Mass and motion has the ability to warp spacetime. Think of spacetime as a mattress and the sun as a bowling ball. When you put the bowling ball on the mattess it makes a bowl shape. This is exactly what happens in space. This bowl in a warping of spacetime commonly felt as gravity. It attracts all things, even bending the path of light. This warping of spacetime is what a black hole is like.

Because you have so much mass in a single point the warpage of spacetime is extremely great. It is so great that it tears a hole in space time. The slope of the curvature reaches infinity. Think of this as a bowl that has no bottom, it just keeps going, like a funnel, only sphereical which is almost impossible to visualize. The center of a black hole is called the singularity. This is where all the mass is. The edge of a black hole is called the event horizon, this is the point of no return if you will. There are accually a few rare exceptions which i will discuss later. The event horizon is a circle around the singularity. This is imaginary, like the equator, you can't see it, it's just a boundery.

Now lets journey into a black hole. As you approach the black hole gravity will become intense and time around you will slow down, but you will not notice this directly. You will see other things begin to speed up, and someone further out will see you slow down. This is due to the warpage of spacetime. You can learn more about this in my section on time. As you go further and further into the black hole you will go slower and slower to someone outside and to you they will continue to speed up. The force of gravity will continue to increase as well. By not your body will have been torn apart, but this is and example. Soon you reach the event horizon, the point of no return, not even light can escape this. Soon you reach a point in which your time completely stops relative to the outside Universe. At this point you will see the entire history of the Universe in an instant. Eventually your body will become one with the sigularity.

Now, how particles escape from a black hole. This involves some very complicated quantum physics but seeing as i've never taken quantum physics i'll try to put it in english. Quantum physics is based on probabilities. According to quantum physics there is a probability that you could instantly dissappear and reappear in china. Of course the time frame for this to occur is much longer than the lifespan of the Universe. The idea we are going to look at is when electrons in an atom change "energy levels", or orbits around the nucleus. You can detect them in the first energy level, then in the second energy level, but not inbetween. Logically, you would think it has to pass through the middle but it doesn't, it simply appears in the next energy level instantly. This is extremely hard to understand but in a black hole, there is a probability that a particle can instantly appear out of the black hole from in it, much like changing energy levels. This is how particles escape. This brings about two questions which i will leave up to you to answer, since I honestly don't know the answers. What happens when a black holeabsorbs so much mass that the singularity cannot remain a single point? What happens if all the mass in the black hole escapes?