On Sat, 5 Jan 2008 07:21:26 -0800 (PST), Sanny wrote:

Is a Black hole as big as Sun. Or it is as small as a Moon. Or just
the size of a FootBall.

The Schwarzschild radius r of a black hole is given by

r = 2GM/c^2

where G is Newton's gravitational constant 6.67 * 10^-11 m^3 / (s^2 * kg),
M is the mass of the black hole, and c is the speed of light, 3 * 10^8 m/s.
Look up some masses and plug them in. This isn't really the distance to
the center of the black hole, which is not well defined, but 2 pi r and
4 pi r^2 give you the circumference and surface area of the black hole.

Does a Black hole has a mass. And does it also have gravity. And Is it
as hot as Sun or very cool.

They have mass and gravity. Matter falling into a black hole will get much
hotter than the sun, but if a black hole had nothing falling into it, the
only radiation coming out would be Hawking radiation, which is extremely
faint for typical-sized black holes, and therefore extremely cool.

I heard Gravity is because a few elementary particle muon/photon
(Gravitons) are exchanged between mass.

Gravitons are not muons or photons. They are a hypothetical new
undiscovered particle.

In that case how these
gravitons are able to go outside the Black hole? As I heard Black
holes even Light can not escape from it.

See the FAQ:
http://math.ucr.edu/home/baez/physic...k_gravity.html

What are Gravitons and do they travel at speed of Light. What is the
mass & charge of Graviton?

If they exist, gravitons have zero mass, zero charge, and spin 2. Because
they have zero mass, the gravitons in gravitational waves travel at the
speed of light. But the gravity that holds you to your chair would be a
quantum-mechanical effect, and there if you want to look at things in terms
of the trajectory of the exchanged particle, you'd have to do a sum over
all trajectories, including ones not at the speed of light.

If a Mass gives out Graviton then I think
slowly it should loose Mass.

Not if the gravitons exchanged transferred momentum but no energy.

Does every particle having mass gives out
Gravitons???

Even particles without mass can absorb and emit gravitons.

--
Jim E. Black (domain in headers)
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