If light cannot escape the gravitational pull of a black hole...then light itself must have mass...what is the

Question

what is the mass of light ?

Answer 1

Photons do not have mass, but they do have energy. Energy couples gravitationally in the general theory of relativity, thus allowing gravity to affect light.
Most people know speed affects time, especially speeds that are a a significant fraction of light speed
Related to this, and also covered in the theory, is that gravity affects time, REALLY!
So now you must be asking does time have mass?
As a character in the game HALO says,
" Hee Hee Hee! "
But seriously real good question!!
Hope this answer was informative and a little bit humorous.
Also if you have a planetarium near you, visit it.
I'm a member of The American Museum of Natural History in NY City; they have an excellent site at http://amnh.org/
Hope this helps
Doug

Answer 2

Although the above answers sound good, they are in fact partially wrong, and you are right. They are overlooking the most well known concept that Einstein came up with: E= mc^2 (E = energy, m = mass, c = speed of light). When we are dealing with black holes, there is no need to differentiate between mass and energy - they are equivalent. So, it it just as valid to say that light is mass or that matter is energy. However, the above answers are good in the sense that it is easier to think of light as an energy wave to answer your question. If you want to know that "mass" of your light, just divide the energy of it my c^2.

Answer 3

The light can't escape because the speed of light isn't fast enough to reach the escape velocity of a black hole at its event horizon.
Its like throwing a ball into the air - it can't escape earth's gravity because it isn't moving fast enough.
At the event horizon of a black hole, the escape velocity becomes equal to the speed of light, so even light doesn't move fast enough to escape if its a tiny bit closer than the horizon.

Answer 4

Personally, I don't think black holes make any light in the first place, so it would be a moot point (if I'm right.) Light is an electromagnetic phenomenon. I don't believe there are any electromagnetic interactions going on inside a black hole, so no light is even trying to get out.

Answer 5

Light has no mass. It's path is curved by gravity not because it has mass but because gravity is a curvature of space-time. The light is going as straight as it can in the sharply curved space-time near a black hole.

Answer 6

wrong assumption.

Light can't escape because the escape velocity of the BH is greater than the velocity of light.

Gravitational acceleration on a test particle doesn't depend upon the mass of the particle. A marble falls just as fast as a bowling ball.

Answer 7

Light is trapped by a black hole because of Gravitational Lensing. Light conforms to the shape of space which is infinitely warped near the singularity.

http://en.wikipedia.org/wiki/Gravitational_lensing

Answer 8

I guess I need to go back to school. Photons are a special form of mass.

Answer 9

Ah, you are venturing into complicated areas here. Light sometimes behaves as a wave and sometimes as a particle. Go here to read about it:
http://musr.physics.ubc.ca/~jess/p200/emc2/node11.html

and this one:
http://math.ucr.edu/home/baez/physics/Relativity/SR/light_mass.html