Faster than light

Originally posted by uzless
Oh you want scientific sources? Sorry, fresh out of those.

To be fair though, the graviton is theoretical right now. Virtually impossible to design an experiment to test their existence.

I think what is important to understand though is not necessarily that the graviton travels fast than light, but rather that the information carried by gravitons may travel faster than light.

When it appears in a real physics journal I would like to see it. Till then, it sounds like untestable unsupportable suppositions.

Originally posted by sonhouse
It's the other way round, just like Electromagnetic forces are mediated by a particle, the photon, if that theory of gravity is correct, the force of gravity is mediated by the particle called the graviton. So far just a theory, no gravitons have ever been detected and don't hold your breath on that one either. We are still trying to just detect gravitatio ...[text shortened]... s apart, pooping out just past the distance of protons and such in the nucleus of atoms.

Yah, I know. That's why I'm struggling with the idea of a graviton being affected by gravity.

Originally posted by avalanchethecat
Yah, I know. That's why I'm struggling with the idea of a graviton being affected by gravity.

I think they currently hypothesize it to be a massless particle.

Originally posted by KazetNagorra
I think they currently hypothesize it to be a massless particle.

And? Photons are hypothesized to be massless and still they suffer gravitational effects.

A graviton could be said to be under the influence of gravity due to self-interaction or graviton-graviton interaction. Just like any mediator in any Field Theory.
The problem here is that the divergence would be a lot more stronger.

Originally posted by adam warlock
And? Photons are hypothesized to be massless and still they suffer gravitational effects.

A graviton could be said to be under the influence of gravity due to self-interaction or graviton-graviton interaction. Just like any mediator in any Field Theory.
The problem he re is that the divergence would be a lot more stronger.

Yeah, true.

Originally posted by KazetNagorra
Yeah, true.

I'm still puzzled with the Burqa wearing women in the Netherlands...

Originally posted by adam warlock
I'm still puzzled with the Burqa wearing women in the Netherlands...

Yeah, well, that's people for you. Much more complicated than physics. 🙂

Originally posted by mtthw
Yeah, well, that's people for you. Much more complicated than physics. 🙂

You don't say... 😛

Originally posted by sonhouse
When it appears in a real physics journal I would like to see it. Till then, it sounds like untestable unsupportable suppositions.

untestable?

Are you saying we can't measure the impact one body has on another?

If i move planet A off course, how long is it before exact same dimensions/composition Planet B that is 1 million km away reacts gravitationally?

Originally posted by uzless
untestable?

Are you saying we can't measure the impact one body has on another?

If i move planet A off course, how long is it before exact same dimensions/composition Planet B that is 1 million km away reacts gravitationally?

If you could do that it would still take about 3 seconds before planet B knew anything about it. Just like if you could teleport the sun 10 light years away instantly, the rest of the solar system would not know for a while. Like about 9 minutes before Earth would react.

Originally posted by uzless
untestable?

Are you saying we can't measure the impact one body has on another?

If i move planet A off course, how long is it before exact same dimensions/composition Planet B that is 1 million km away reacts gravitationally?

And let's be honest, we don't know that gravity is propogated by gravitons.

Originally posted by avalanchethecat
And let's be honest, we don't know that gravity is propogated by gravitons.

Whether or not gravitons are the arbiters of gravity has nothing to do with the velocity of changes of gravitational forces such as the thought experiment where a star is teleported out of its system. It seems to me you WISH gravity to move at 20 X c and therefore are predisposed to believe any report that supports that wish.

For instance, in quantum theory, particles or systems in superpositional states allow one particle to instantaneously change to a known state when its partner does likewise but quantum theory also unequivocally states that information in a quantum state cannot transmit information faster than c, in other words, quantum theory says we can never use that instantaneous change to make a faster than light communication system, unfortunately.

Originally posted by sonhouse
Whether or not gravitons are the arbiters of gravity has nothing to do with the velocity of changes of gravitational forces such as the thought experiment where a star is teleported out of its system. It seems to me you WISH gravity to move at 20 X c and therefore are predisposed to believe any report that supports that wish.

For instance, in quantum the ...[text shortened]... r use that instantaneous change to make a faster than light communication system, unfortunately.

Are you aiming this at me? I have no desire for gravity to travel faster than light! It can go on the bus for all I care. I'm sceptical of EVERYTHING, including, but not limited to, the apparent reality that we're all trying to get our heads around here. And I wasn't aware that quantum theory states that information cannot travel faster than light. Could you reference that please?

Originally posted by avalanchethecat
And I wasn't aware that quantum theory states that information cannot travel faster than light. Could you reference that please?

1 - In Physics the notions of information and energy are virtually interchangeable.
2 - In Physics there is the concept of group velocity and phase velocity. These are related concepts, but are calculated in different ways and can have different values for the same situation.
For instance non-monochromatic light traveling through a dispersive medium has different values of phase velocity and group velocity (this basically a ray of light composed of different frequencies going through a prism)
3- Phase velocity can be bigger than c but group velocity is always less than c. This is a rigorous mathematical result.
4 - The energy of a wave packet can also be shown to travel at a velocity that is equal to the group velocity.

Thus in QM information always travel at a velocity that is less than c.

The situation of the two particles with different spins doesn't fall on the realm of group velocity/phase velocity though. It is a hard problem that even today is being argued by a large number of prominent physicists. This is called the entanglement problem and the views range from being solved to not being a problem at all.

Being the normal way for me I argue on the basis this problem only arise if we stick to the notion that Fourier Analysis is the natural too to use when dealing with QM. A lot of people have used Wavelet methods in QM and in the context of wavelets the entanglement problem is very neatly solved.
I know a good reference that discusses all of this, but unfortunately it is in portuguese...

Originally posted by adam warlock
1 - In Physics the notions of information and energy are virtually interchangeable.
2 - In Physics there is the concept of group velocity and phase velocity. These are related concepts, but are calculated in different ways and can have different values for the same situation.
For instance non-monochromatic light traveling through a dispersive medium h ...[text shortened]... .
I know a good reference that discusses all of this, but unfortunately it is in portuguese...

From Brazil? My daughter and her husband teach music and physics respectively at Federal University and they might be convinced to translate if you can provide the link.