Black holes

What are the black holes ?

A black hole is an object that is super thick strong gravity. There are two parts in a black hole, a singularity and a horizon. If you have a disk from a black hole through the center looks like:

The event horizon is where the gravity is so strong that even light is absorbed by the black hole. Even if the horizon is part of a black hole, not a tangible object. If you fall into a black hole would be impossible for you to know when the event horizon. For a mathematical derivation of the radius of an event horizon, see below.
The singularity is not actually a tangible object o. The general theory of relativity, singularity is a point of infinite curvature of space-time. This means that the force of gravity becomes infinitely strong at the center of a black hole. Everything falls into a black hole crosses the horizon, including light, will reach the singularity of a black hole. First of all, reach the singularity is torn by the force of gravity intense. Even atoms are torn apart by the force of gravity.

The formation of a black hole:

Imagine a star that is much larger than our sun, and a mass, called a critical mass sufficient to cause a black hole to form. What prevents the star collapses into itself and is a black hole?The answer is that the pressure caused by nuclear reactions in the Sun When the fuel that feeds the nuclear reactions is exhausted massive star can not keep for himself. Then it collapsed to a black hole.
Interestingly, when a black hole is formed by a collapsed star is actually impossible for the latter stages of the formation of black hole of the stationary external reference can be seen. An external reference is a place where you can observe the formation of the black hole, like an astronomer on earth by far. Furthermore, it is impossible for an object falling into a black hole to see. This does not mean that everything seems to freeze just before entering a black hole. If an object falls into a black hole is growing weaker and weaker from the standpoint of an observer.When an object is placed on board a black hole is completely black. This effect, called gravitational redshift, caused by the immense gravity near the outside of a black hole.

Cool things about blacks holes:

First, if it is close enough to a black hole you see the back of the head! This effect, called an Einstein ring is caused by the force of gravity around a black hole. When approaching a black hole at some distance from the light, leaving the back of the head will travel even if the space is determined by the severity of that between the eyes.
Another interesting thing is that blacks holes can destroy data. The destruction of the information is not allowed by quantum mechanics, as Hawking has concluded that the normal rules of quantum mechanics can be applied to the black hole! John Preskill of Caltech has an article about this which should be accessible to nearly all readers.