霍金与黑洞学说【英文】Hawking分析

4
Space Warps
If
we imagine the spacetime as a “rubber sheet”, then any mass would produce warpings in it. Since black holes produce very strong gravity, spacetime is significantly warped (curved) around them. We see strong light-bending and gravitational redshift.
3 June 2006
Hawking and Black Holes
Outline: The scientist Information and black holes Hawking radiation Detection of black holes Bets on black holes
The Scientist
Born
1942 1st class honours from Oxford, after “not very much work” Symptoms of ALS during Oxford years PhD and Research Fellow in Cambridge Discovered Hawking radiation in 1974 “A Brief History of Time” published in 1987 Numerous honorary degrees and awards Outspoken for world peace, welfare of the handicapped, and other current issues
buttoning,
writing, turning a key in a lock Atrophy of hand muscles Atrophy of tongue Difficulty chewing food Difficulty swallowing (dysphagia) Difficulty speaking Muscle cramp
5
The Black Hole Radius
2GM rs 2 c


For any mass, there is a smallest radius beyond which the object becomes a black hole. This smallest radius rs is called the Schwarzschild radius. Hawking: This defines the size of a black hole, and it depends on the mass only. Anything smaller than its corresponding Schwarzschild radius becomes a black hole.
Amyotrophic Lateral Sclerosis
肌萎縮性脊髓側索硬化症 Also called Lou Gehrig’s disease Symptoms: Difficulty standing, walking, or running
wenku.baidu.com Clumsiness – Frequent tripping or falls Difficulty with fine hand motions such as
v escape

2GM r
Light rays
The escape velocity increases with mass and decreases with radius. If vescape> c, then light cannot escape and we have a black hole.
7
Event Horizon and Singularity
8
No-hair Theorem


Hair here means something complicated (e.g. different styles, colors, perms, etc…). Black holes have no hair because they are simple. Only three things completely characterize a black hole (Hawking 1972): – mass – angular momentum – electric charge
Black Hole

Black holes represent the final victory of gravity. A black hole is black because gravity is so strong that light cannot escape. The escape velocity at a distance r from the center of an object with mass M is
6
Dissecting a Black Hole
• A non-rotating black hole is particularly event horizon simple. • There is a point at the center called the singularity (奇點). It has zero size and infinite density. In fact, its properties cannot be described by currently known physics. • The event horizon (穹界) is a sphere centered at the singularity with radius equal to the Schwarzschild radius of the black hole. • What is inside the event horizon cannot be known by anyone outside because even light cannot escape out. singularity