If they are real, what exactly do gravitons do?

[glueball8]

Now I might be piecing this together. I thought that the Earth being in the way would dicipate the electromagnetic force, because less photons are recieved. And the only reason some are received is because they are bent around the Earth due to gravity. But the electromagnetic force runs on virtual photons. They are evidently so unreal that they can jump right through the earth, I think. I don't know for sure, or how. But the electromagnetic force must be able to get to the other side somehow.

So, now I ask, is the electromagnetic force dicipated by the Earth's presence? If so, I still don't have an answer to what's bothering me. If not, then we're good.

A few questions:

-Does photons interact with itself?
-Does gluons interact with itself? If two gluons can create a gluon does that mean it interact with itself?
-How can gravitons interact with photons?
-What would the properties of gluon be like if its power is decreased significantly, to about gravity. That means it can travel farther?

 

[tom.stoer]

I'll try to answer that

Photons can only interact with photons indirectly via virtual electron pairs. Two photons cannot exchange a virtual photon, but the two photons can decay into two virtual electron-positron pairs. The particles in these pairs can exchange virtual photons. Because of the many virtual particles involved this process is highly suppressed and as far as I know not measurable directly.

For gluons you already gave the answer: yes, by exchange of a virtual gluon.

Regarding gravitons I can only repeat what I have mentioned a couple of times here. The electromagnetic field interacts with the gravitational field (light deflection near the sun, measured during eclipses). But if you try to quantize gravity like an ordinary QFT (which may provide some notation of gravitons and describe this scenario including quantum corrections) the theory becomes inconsistent (non-renormalizable).
0) In perturbatively quantized QG you have a notation of gravitons, you have a coupling of gravitons to other gravitons and to photons, but if you try to calculate a cross sections or other physical quantities, the theory gives you infinite answers; this cannot be cured and therefore it does not make sense to talk about vitual gravitons (at least not in this simple picture).
So you have to try other approaches in quantizing gravity:
1) supergravity may eventually allow to describe photons and gravitons; for gravitons it's fine, they are there. But I don't know if there's a realistic SUGRA theory containing all particles and forces of the standard model; I haven't seen any! And SUGRA may cure the problem of non-renormalizibility; there are steps into that direction but I do not know if there is a solid proof; I haven't seen any!
2) the same for string theory; up to know there's no low-energy limit which reproduces the standard model exactly; and there is no solid proof of renormalizibility and/or perturbative finiteness.
3) in LQG the situation is such that photons couple to a "quantized gravitational field", but in all approaches I know you somehow loose the notation of gravitons: the elementary quanta of the gravitational field are fundamentally different from something like quantized plane waves. This is not a drawback but a feature: the theory need not produce gravitons (nobody has ever detected a graviton) butmust instead provide a consistent quantization scheme (a replacement of the perturbative one).

Good question. What do you mean by reducing the "power of the gluon"? do you mean the strength of the strong coupling? I would say that glue balls would still exist, but they would have less mass and would be much larger.

 

[Ultimaton]

I’m having a hard time believing gravitons exist. This is how I’m thinking:

We know that Mass distorts time-space like the Einstein example of the bowling ball on the trampoline warping the fabric. Another ball will travel around the bowling ball due to the warped space [warped fabric]. But that doesn’t explain everything.

Since mass is defined as an objects inertia, or resistance to force casing a change in it’s velocity through the medium of Space-Time. Therefore the mass of the object could increase, as it is accelerated faster.

I like to think of Space-Time like the propagation of sound in air. As an airplane travels through the air, it creates a sound pressure wave. That is the warping of the atoms, forcing atoms into each other, transferring that wave from atom to atom through the medium. You reach a maximum speed, which is the speed this wave can be propagated through the medium: The speed of sound.

Now Space-Time works in a similar fashion. When a mass is accelerated faster, it reaches a point where this shock wave interferes with the velocity, requiring more and more force to obtain higher speeds. Since mass is the resistance to force which causes velocity changes, that objects mass is increased, thus will never obtain that maximum speed, due to the increased resistance.

When the Earth travels through the warped Space-Time caused by the sun, it encounters this warped Space-Time. Adding it’s own mass related warp to the Space-Time itself, it encounters more resistance to velocity change, and realizes a time warp towards the sun, which translates into a force which we have called gravity.

Therefore, Gravity does not exist. We realize the effects of warped Space-Time, and thus ‘feel’ a force towards this warping.

The only graviton I can comprehend, is the speed at which mass related warping can propagate through the medium of Space-Time. That is C.

Does this make sense?