Mass-less particles speed

[Silvestru]

Hello,

 

I was wondering about something and was hoping to get some clarification.

As I understand, the gluon is a mass-less particle and it always moves at the speed of light.

 

 

 

The behavior of mass-less particles is understood by virtue of special relativity. For example, these particles must always move at the speed of light

 

But the gluons are also what hold together quarks in a proton. So how does it "always move at the speed of light" and is also part of a construct which contains particles with mass?

[Strange]

I think there are two possible answers (I'm not sure which is more accurate).

 

1. The gluons in a proton do travel at the speed of light (within the proton).

 

2. They are "virtual gluons" as force carriers and are not constrained to travel at (or even below) the speed of light.

Good quick thread about virtual particles here: http://www.scienceforums.net/topic/105297-why-are-virtual-particles-called-such/

[imatfaal]

The four forces are mediated by exchange particles - gauge bosons - which kind of "go from one object to the other" and thus create the force. This is a gross and dangerous simplification. Most of the time (unless an interaction occurs) these are virtual particles (whilst the force is anything but). The interaction between the two objects which is mediated by the exchange particles is limited to the speed of light - thus the exchange particles are limited to c for the massless ones (graviton, photon, gluon) and less than c for the massive one's (W, Z).

 

QFT can be visualized and calculated by Feynman diagrams - many of the gauge bosons in the calculations and predictions of QFT are virtual particles and I do not believe that they are constrained. These virtual particles must remain internal to the calculation, ie do not externally interact and are loops in diagrams; thus they do not really become a problem in SR in terms of FTL causality.

 

Note - due to Colour Confinement - you do not get free gluons. So it is all a bit of a moot point

[Mordred]

To add a bit of detail on the Feyman diagrams. The solid external lines are observable real particles. The internal lines (virtual particles) are represented by squiggly lines. Just a side note to make reading them easier

Edited May 5, 2017 by Mordred