What causes gravity?

Ken Hemingway · Posted: Sun Apr 10, 2005 6:32 pm Post subject: Re: What causes gravity?

Rellimlk

Thanks for the summary. I think for this to begin to jell I'd need answers to two further questions.

1. How does exchange of particles cause force in the first place? I think it has something to do with the momentum of the exchanged particle (somehow negative for attractive forces), but this is puzzling when the exchanged particle has no mass (as with the photon).

2. How doe the particle exchange theory fit in with the warped space-time theory fo General Relativity? Einstein spent half his life looking for a unification of electromagnetism and gravity with no success. Have the recent advances cast any light on this question?

rellimlk · Posted: Sun Apr 10, 2005 7:57 pm Post subject: Re: What causes gravity?

Quote:
Einstein spent half his life looking for a unification of electromagnetism and gravity with no success. Have the recent advances cast any light on this question?

String theory and M-Theory (a meta-theory that takes different versions of string theory that seem to conflict and reveals a common substructure) is currently the the widest held (perhaps only) theory that unifies gravity with the other 3 forces. The messenger particles for the other 3 forces, by the way, have been experimentally verified (if I remember correctly) in atom smashing.

Quote:
How doe the particle exchange theory fit in with the warped space-time theory fo General Relativity?

I don't have a good answer to that...except that the gravitational field works the same way as any other force field (electromagnetic, for example). Gravitons are simply the smallest, fundamental component. It is almost a misnomer to call them particles--it is more like a packet of force. In some ways, matter PARTICLES with a mass should also be understood to be fields just like forces--since they are really just energy vibrations. But we are very accustomed to thinking in terms of tiny bits of solid stuff that things don't get phrased that way. It is tied up with the E=mc2 which describes the interchangeability of energy and mass.

Quote:
1. How does exchange of particles cause force in the first place? I think it has something to do with the momentum of the exchanged particle (somehow negative for attractive forces), but this is puzzling when the exchanged particle has no mass (as with the photon).

You mention mass as though for something to exist physically (that is have physical effects on things)it has to have mass. This is a very fundamental assumption that can be difficult to get beyond...it is so integral to our experience of the world. When we experience the mass of an object we experience its resistance to being moved (accelerated). But accelerated in relation to what? And what is it that makes a thing need to stay in the same state? What gives a thing MASS?

One answer provided is what they call the Higgs Ocean...a universal force field that is left over from the big bang. All the different vibrating strings behave differently when passing through the Higgs Ocean. A string that has mass (like an electron or bottom quark) are strings that can not move unimpeded through the Higgs field. Mass is simply the measure of that strings resistence to moving through the Higgs Ocean. A photon, gluon or graviton can move through the Higgs Ocean unimpeded. Once one looks at mass in this light, if one assumes that particles with mass can act upon other particles when they come in contact, there is no reason why a force particle would not act upon other particles when they come in contact: both are filaments of energy, the difference being that matter particles are impeded by the Higgs field and force particles are not.

I don't think that answers your question...I think I just gave a new backdrop for it. My point is that it is just as valid a question to ask where does matter get its "matterness" as to ask where does force get its "forcefulness." The answers would seem to be equivalent.

I think it may be time for a PhD to step in: I'm not sure how much more I can add to this subject.

Interbane · Posted: Sun Apr 10, 2005 8:24 pm Post subject: Re: What causes gravity?

I've read "The Elegant Universe" by Brian Greene years ago and caught the gist that even though extrapolations can be made of the current theory to predict what a Graviton would be and act like, it is just as good as any other explanation until the predictions are observed.

I haven't read the newer book yet, I may have to do that. Hopefully it sheds a bit more light on things for me. I hear they're building a new collider also, one that may be able to observe previously unobserved particles. I trust Scientific American to keep me up to date there.

Ken Hemingway · Posted: Mon Apr 11, 2005 7:48 am Post subject: Re: What causes gravity?

Interbane wrote: You mention mass as though for something to exist physically (that is have physical effects on things)it has to have mass.

No, I don't think that. But to have momentum without mass seems problematic - p = mv?

grmanny · Posted: Tue Apr 19, 2005 6:15 pm Post subject: Re: What causes gravity?

this interesting


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