Last I heard, scientists are still looking for gravitons, and I have even heard dopers on thses board refer to gravity ‘waves’ and ‘particles’.
This, to my admitedly limited understanding on the subject, seems to disagree with Special relativity.
Special relativity tells us that the orbital paths followed by planets, our moon, man-made satellites, in short: gravity, is nothing more than the motion of bodies through warped space-time.
That is, massive objects warp space-time around them causing the phenomena we term ‘gravity’.
If that is true, then what is the point of looking for gravitons, gravity waves or particles? It would appear to me that special relativity tells us that there are none. Objects are simply following the trajectory of warped space-time.
And yet I must be wrong since scientist still refer to these things. Could someone explain this better to me?
Ahhh, ok. Silly me, yes I just took the fact that massive bodies warp space-time as a given without asking, how?
How unscientific of me!
So in a related question, since we don’t know HOW this occurs, what makes us think that particles of gravity have anythign to do with it? And what makes us think there even ARE particles at work?
I’m guessing that’s a complicated question, so a link to a reference source would be much apreciated
Well, the three other forces we know about all have an associated particle to carry them. Electromagnetism has the photon, the nuclear strong force has gluons and the weak force has W and Z bosons. So, it’s natural to assmume that gravity also has a particle associated with it. Plus superstring theory contains within it one entity whose properties exactly match the predicted characteristics of the gravition. In other words, superstring theory not only explains gravity, it requires it.
Special rleativity doesn’t deal directly with gravity, though it can be fitted into the framnework of SR. It is general relativity that introduces the concept of gtravity as curved space-time.
Gravitons are very firmly predicted by theory (though no complete theory of quantized space-time exists yet), but so far due to the nature of gravity none have been detected. Infact several of the properties that i hould have are also well predicted such as that it shoild be massless and have a spin of 2.
I would disagree with this. Even Einstein’s first paper on special relativity dealt with the effects of acceleration. General relativity makes gravity and acceleration equivalent, though, and says any frames of reference are equivalent, even rotating ones.
In Special Relativity, your coordinate system must be inertial and the axes must be orthorgonal. This is a special case of General Relativity that allows general coordinate systems with (possibly) curved axes and not-necessarily-inertial frames. In SR, objects can accelerate, but not your coordinate systems.
In SR, the speed of light is constant and has the same value in all inertial reference frames. In GR, the speed of light is not constant. In both, nothing can travel faster than light travels.
I thought that “gravitons” are VIRTUAL particles predicted by the (Heisenberg?) principle that all field (ie, wave) phenomena can and MUST be equally describable by particle emission-and-absorption models.
