Light

[ramparts]

It's a possibility. It really depends how you interpret these things. You can conceive of gravity as being a curvature in spacetime, but you can also just as well conceive of it as a field. Mathematically, they're the same. So if you do the whole quantization thing to that field, you get gravitons. That said, we don't know how quantized gravity works (when you quantize gravity you run into some pretty big issues), so it is possible that the answer will involve no gravitons, but I'd say that's unlikely at this point.

 

[a_lost_packet_]

Well, I guess there goes my nobel prize :lol:

But if gravity is just caused by matter putting a "dent" in the fabric of space-time, then would it be possible that there is no graviton responsible for the force of gravity, that it is different from the other forces? This is all way above me, so it may be a stupid question :? .

It may be better to look at it as a question of communicating "mass." What particle identifies a body as bearing mass? The fabric of space-time responds to mass. There are boundaries dependent upon mass. Therefore, maybe there is a messenger particle? That messenger particle would tentatively be named the graviton which would communicate a body's mass and the fabric of the Universe would naturally respond to that.

 

[MrUniverse]

maybe.. and this is a total stab in the dark, the thing with a black hole is that the gravity was already there outside when the star originally collapsed.

What I am saying is, perhaps if there were some way to reach into a black hole and change its mass, we would not know. We can never see what is currently inside, only what it was at the instant it passed the event horison.. infact we never see it passing that point. From out point of view it is frozen without ever quite reaching it. So the gravity we experience from a black hole does not come from inside the event horizon.

I think I understand what you're saying, basically: gravity gets held near the event horizon. :?
This made sense to me at first.
However, if this were the case then how could gravitons affect masses at a distance from the event horizon if they are held stationary?

virtual particles

Are you saying that the gravitation field on our side of the event horizon is maintained by the gravity of virtual particles popping in and out of existence due to the gravitational field from before the collapse?
AFAIK, that field would produce a huge amount of particles and antiparticles. (Isn't an equal amount of matter and antimatter produced when they "pop" into being?) ; and if it were in fact a mass of virtual particles and virtual antiparticles sufficient to sustain the gravitational field of mass that entered the event horizon, then wouldn't we see the release of energy equivalent to the complete annihilation of the totality of mass?
-I'm sure I'm not understanding your explanation.
-I'm also not 100% sure about the annihilation of antiparticles.

Sorry about long post. It's just that this is the most interesting topic I've seen on this BBS.

 

[yevaud]

Remember, Gravity has been at least observationally shown to be limited by C. So when encountering an Event Horizon, gravity is held just as is light. It cannot quote escape unquote.

 

[ramparts]

maybe.. and this is a total stab in the dark, the thing with a black hole is that the gravity was already there outside when the star originally collapsed.

What I am saying is, perhaps if there were some way to reach into a black hole and change its mass, we would not know. We can never see what is currently inside, only what it was at the instant it passed the event horison.. infact we never see it passing that point. From out point of view it is frozen without ever quite reaching it. So the gravity we experience from a black hole does not come from inside the event horizon.

I think I understand what you're saying, basically: gravity gets held near the event horizon. :?
This made sense to me at first.
However, if this were the case then how could gravitons affect masses at a distance from the event horizon if they are held stationary?

I'm not sure what you're getting at here. What do you mean by gravity "getting held" somewhere?

virtual particles

Are you saying that the gravitation field on our side of the event horizon is maintained by the gravity of virtual particles popping in and out of existence due to the gravitational field from before the collapse?
AFAIK, that field would produce a huge amount of particles and antiparticles. (Isn't an equal amount of matter and antimatter produced when they "pop" into being?) ; and if it were in fact a mass of virtual particles and virtual antiparticles sufficient to sustain the gravitational field of mass that entered the event horizon, then wouldn't we see the release of energy equivalent to the complete annihilation of the totality of mass?
-I'm sure I'm not understanding your explanation.
-I'm also not 100% sure about the annihilation of antiparticles.

Sorry about long post. It's just that this is the most interesting topic I've seen on this BBS.

Well, no, I wouldn't say the field is maintained by the gravitons. I'm no expert on field theory, but my impression is that the causality is the other way around - the field creates the virtual particles, in the sense that the particles are merely "excitations" of the field, that is, little pockets where (due to quantum effects) the energy of the field gets bumped up a bit.

You're bringing anti-particles in (I think) prematurely. I don't see why they'd need to be produced. Virtual particles and anti-particles aren't the same thing.

 

[MrUniverse]

kelvinzero wrote:maybe.. and this is a total stab in the dark, the thing with a black hole is that the gravity was already there outside when the star originally collapsed.

What I am saying is, perhaps if there were some way to reach into a black hole and change its mass, we would not know. We can never see what is currently inside, only what it was at the instant it passed the event horison.. infact we never see it passing that point. From out point of view it is frozen without ever quite reaching it. So the gravity we experience from a black hole does not come from inside the event horizon.

I was interpreting the above post as meaning that the gravitons from before the black hole formation, get "frozen" outside the event horizon. I was saying I didn't see how gravitons could affect anything if they were "frozen" outside of the event horizon. Gravitons must reach something to gravitationally affect it, right? :?

If virtual particles aren't a source of gravitation outside of the event horizon then how do they come into play?

I think we both might be wrong about the particle/antiparticle thing.

In order to conserve the total fermion number of the universe, a fermion cannot be created without also creating its antiparticle; thus many physical processes lead to pair creation. The need for the normal ordering of particle fields in the vacuum can be interpreted by the idea that a pair of virtual particles may briefly "pop into existence", and then annihilate each other a short while later.

Thus, virtual particles are often popularly described as coming in pairs, a particle and antiparticle, which can be of any kind. These pairs exist for an extremely short time, and mutually annihilate in short order. In some cases, however, it is possible to boost the pair apart using external energy so that they avoid annihilation and become real particles.

-http://en.wikipedia.org/wiki/Pair_production
I may be way off base, but seems like when a matter particle pops into existence its antimatter counterpart does the same. However, force carrying particles (like gravitons) don't do this.?.
So apparently, some virtual particles are matter/antimatter pairs.

Right after I posted that last post, I realized that the energy for virtual particles comes from "vacuum energy" and that is where I suppose it goes when the particles annihilate.

 

[kelvinzero]

I dont know about fields vs gravitons or such.

Mainly I am saying that information cannot escape a black hole, because we cannot transmit information faster than light. Doing so tends to create paradoxes. Whatever gravity is, it cannot be a way of passing information out of a black hole. This includes information about whether there is even really something still inside the black hole.

 

[ramparts]

MrUniverse - Pretty much. Fermions (matter particles) are required to be pair produced, for physical reasons, but bosons (force carriers) don't.

 

[MrUniverse]

Still vexed about this. Is the gravity coming from the singularity at the center of the black hole? Or is the field around the event horizon where the gravity is coming from? If there were a spherical region around the black hole where the gravitational field that is felt outside of the event horizon, then is that why you can supposedly cross the event horizon of a super-massive black hole before you get spaghettified?
I'm thinking of it kind of like this: imagine a hollow sphere. The mass is on the out side. Now imagine a larger sphere with the same mass. The surface gravity of the smaller sphere would be greater because the angles at which gravity is acting upon you are more acute. The gravity is more focused.
If both a "normal" black hole and a super-massive black hole were pulling you from the singularity, then why would the huge one not spaghettify you before the event horizon?
I just don't get it.

EDIT:
Sorry, never mind. Totally forgot that the force of gravity is inversely proportional to the square of the distance. :roll: :roll:

 

[ramparts]

The gravity is "coming from" a field that exists throughout spacetime (not just outside the event horizon - there's obviously gravity inside the horizon too. There's actually nothing special about the horizon physically, except that it happens to be related to this milestone of the speed of light). I put that in quotations because it's sort of misleading to think of the field as constantly emanating from an object - once it's there, it's there.