steph and black hole hair.

I'm not sure of black hole hair *ahem* but maybe I'll talk about black hole from a very entry level. Maybe Stehpanie can enlighten us further. =)

In the outer space there are interstellar gases and clouds. After 500,000yrs they will turn into a protostar which is a baby star. It will grow up to become a star, subsequently run out of fuel and becomes a red giant...(no, not monster, but giant). From here, it will either undergo a small explosion called nova and turn into white dwarfs, or go thru a gigantic explosion called supernova (not the BT site suprnova) and turn into neutron stars or black holes. (I can't understand why is it called Cafe Nova, not as if there was an explosion or what and turn into 3-in-1 coffee)

During the explosion from the surface of the core, we also have implosion occuring at the inner most core. A black hole appears if the implosion is massive enough.

Now, I'm going to do some maths here. We know that kinetic energy is 1/2(mv^2), gravitational potential energy is -GMm/r. To find the equilibrium point we put 1/2(mv^2)-GMm/r=0, giving us the escape velocity to be root(2GM/r). If we replace the v with c, the speed of light, and rearranging the equation, we will have r=2GM/c^2. This r is called Schwarzschild radius, at which even light ray cannot escape the gravity pull of the star. This means that even light will be sucked into the black hole! To be exact, the Schwarzschild radius will define a surface called the event horizon. Inside this event horizon, things will be compactified such that their volume will become zero (and density will become infinity). The point at whcih the volume reaches zero is called singularity.

No hair theorem says that a black hole has almost no "hair" (they could have said "no dust theorem".. why no hair?), and the only "hair" it has are mass, angular momentum and electric charges. In other words, a black hole only remembers the mass, angular momentum and electric charge of the matter which falls into it. Anyway Stephen Hawking has presented a new theory against the no hair theorem...

Argh these are getting so deep.... continue next time if my mood feels like it.