Black Holes

A black hole is an object with a concentration of mass great enough that the force of gravity prevents anything from escaping from it except through quantum tunneling behavior. The gravitational field is so strong that the escape velocity near it exceeds the speed of light. This implies that nothing, not even light, can escape its gravity, hence the word "black." The term "black hole" is widespread, even though it does not refer to a hole in the usual sense, but rather a region of space from which nothing can return. Theoretically, black holes can have any size, from microscopic to near the size of the observable universe.

Black holes are predicted by general relativity. According to classical general relativity, neither matter nor information can flow from the interior of a black hole to an outside observer. For example, one cannot bring out any of its mass, or receive a reflection back by shining a light source such as a flashlight, or retrieve any information about the material that has entered the black hole. Quantum mechanical effects may allow matter and energy to radiate from black holes; however, it is thought that the nature of the radiation does not depend on what has fallen into the black hole in the past.

The existence of black holes in the universe is well supported by astronomical observation, particularly from studying supernovae and X-ray emissions from active galactic nuclei.

Contents [showhide]  
1 History

2 Qualitative physics

2.1 The event horizon
2.2 The singularity
2.3 Entering a black hole
2.4 Rotating black holes
2.5 Entropy and Hawking radiation

3 Reality of black holes

3.1 Formation
3.2 Observation
3.3 Have we found them?

4 Micro black holes

5 Mathematical physics

6 Recent discoveries

7 Alternate models

8 Related topics

9 External links

10 Further reading

[edit]
History
The concept of a body so massive that not even light could escape from it was put forward by the English geologist... [continues]

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