Question & Answer

Question:
What would happen if two Black Holes merged?

Answer:
The size of the event horizon is determined solely by the mass and spin (if it happens to be spinning) of the black hole. If two were to orbit each other (or any two massive bodies such as neutron stars) a lot of energy in the form of gravity waves would be emitted. This will leak energy out of the system, until the two objects merge. It would appear that the smaller one was swallowed by the larger, but it really is a merger around their common center of mass, and the event horizon would grow according to the new higher mass.

Question:
If light doesn't have a mass, how can it get sucked into a black hole?

Answer:
In a Black Hole, light traveling outwards towards an event horizon is pulled back by the very strong gravitational field, because of the warping of space-time inside the event horizon, regardless of the lack of a photon mass. This prevents light from ever escaping the Black Hole. Furhter more, photons, particles that make up light have a very minute mass, and is so little that it is regarded as none.


Question:
Are Black Holes transports to other worlds, other universes?

Answer:
In principle, the mathematics of black holes show that they might be able to transport you to another region of space or possibly another universe. However, the mathematics also shows that the connection only lasts for a fraction of a second at a time, and that the link to other universes depends on a specific set of conditions which scientists do not believe to have existed. Even if it were likely, however, the strong gravity field of the black hole tears apart any material falling into the hole. Further, black holes, have infinite depth and thus, scientists do not believe on “another” side.


Question:
Who was the first person to discover a black hole and what was the date?

Answer:
Black holes cannot be observed directly and therefore cannot be 'discovered'. When light is sucked in, the blackhole is outlined by a rim of light however.


Question:
How could I model a black hole for a science project?

Answer:
If you can get hold of a sheet of rubber, or some other fabric that stretches. You can use that as an analogy of space: Put something heavy on it, that would be like a normal star. Roll a little marble around it.
Now make a hole in the sheet, and pull the edges of the hole down. That would be like a black hole.


Question:
What happens to the material absorbed into black holes?

Answer:
You probably have heard about Einstein's famous equation, E = mc^2, which gives the energy associated with material of a given mass m. When material falls into black hole, a process called accretion, usually about 10% of the mc2 energy gets radiated away as the material approaches the black hole. The other 90% gets absorbed into the blackhole and simply adds to its mass. In some cases, the material won't have a chance to radiate much energy and essentially all of the mass goes right into the blackhole.


Question:
Wouldn't the black hole finally fill up?

Answer:
Actually, a black hole is already essentially a geometric point, with effectively infinite density. There is no inherent limit to the mass of a black hole. There is a region around black holes called the event horizon. Once anything, including light, crosses the event horizon, it can never escape. This is what gives the black hole its name. The size of the event horizon gets bigger as the black hole gets more massive. This allows the black hole to "grow", in a sense, as more mass falls in. There is very strong evidence that some galaxies have black holes as massive as a billion Suns at their centers (one example is the Sombrero galaxy)


Question:
Can life be maintained within a black hole?

Answer:
No, anything that falls into a black hole will get heated to very high temperatures (this is how the 10% of the energy gets radiated away... the material gets very hot, in a process similar to how meteors and space debris burn up due to friction as they enter the Earth's atmosphere). Also, once the material gets very close to the blackhole, tidal forces will stretch it very thin.

Question:
Can one see a black hole?

Answer:
By definition, you can't see a black hole at all. Again, not even light can escape from within the event horizon. Interestingly, though, black holes warp space so much that if you could orbit a black hole close to the event horizon, you could see the back of your own head... light reflecting from the back of your head would get bent around the black hole so that you could see it.

This is what a black hole looks like.