Do black holes have gravity?

Question

Everybody knows a black hole is any object with an escape velocity greater than the speed of light. Light is just too slow to escape a black hole. Since gravity travels the speed of light, doesn't that mean gravity can't escape a black hole either?

Answer 1

This is actually a very astute question, and the difficulty in answering it stems from the fact that there is no quantum theory of gravity.

Black holes are a prediction of general relativity, which models the effects of gravity as a curvature of space time. A black hole has so much concentrated mass that it curves space to a singularity, and once that singularity exists it will continue to do so unless something happens to let the mass escape.

Quantum theory models the universe in terms of particles and the interactions between those particles in term of the exchange of "virtual" mediating particles. For instance, the electrostatic force is mediated by an exchange of photons. This would clearly present a problem if the photons could not escape to be exchanged.

However, there is no quantum theory of gravity so we cannot be clear that the force behaves in the same way.

But one thing to think about is the fact that black holes do, in fact, radiate energy - so much so that they may in some cases evapourate. The reason they can do this is because of the way quantum mechanics behaves.

Throughout space particle-antiparticle pairs are created and then anihilate one another all the time - this is allowed by the Heisenberg principle provided they stay in existence for a short enough time (delta E delta T <= h bar). Now if this happens at the event horizon, one particle can be trapped by the black hole while the other escapes. The trapped antiparticle will anihilate with a particle inside the black hole, reducing its mass. The particle will escape.

Answer 2

Yes, black holes have gravity. They are composed of a very large mass.

Scientists often refer to light as light particles. If they are particles that means they have mass, even though that mass may be very, very small. All mass exhibits a gravitational force or a want to attract itself to another body of mass. That mass is dependent on the mass/size of both bodies and the distance that separates those bodies of mass.

I've never seen where a scientist has said that light has gravitational force, but I think it must (be it ever so small). And the only time we get to see that is when it passes a very large body. Large celestial bodies will bend the direction that light travels when light travels past it. A black hole exhibits so much gravitational force that if the light is too close it will be pulled towards the mass that is the black hole.

They say in a nuclear reaction that matter is destroyed. I think it may be just transformed into smaller light particles. Maybe a black hole has enough energy to transform those light particles back into what is traditionally called matter, making Einstein's equation work in both directions, not just mass to energy.

Answer 3

A black hole is a concentration of mass great enough that the force of gravity prevents anything past its event horizon from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). The gravitational field is so strong that the escape velocity past its event horizon exceeds the speed of light. This implies that nothing, not even light, inside the event horizon can escape its gravity. It is, however, theorized that wormholes can provide an exit path for energy or matter. The term "black hole" is widespread, even though it does not refer to a hole in the usual sense, but rather a region of space from which nothing can return.

Answer 4

The strength of gravitiy on a black hole is extremely great compared to the gravity near 'normal' stars.
Gravity itself does not travel. It is a whobble in spacetime.
Only change in the field travels as a graviton with speed of light.

Answer 5

nothing can escape the gravitational force of black holes not even light.

Answer 6

I don't think gravity travels. If 2 bodyes have mass they just atract each other.

Answer 7

there is no gravity, everything just sucks.

Answer 8

oh yes

Answer 9

depends on how long you screw