Massless Particles: Force Bearing & Propagation Speeds

[geordief]

It looks to me like all the massless particles so far discovered may be force bearing particles, there being 3 of them.

Am I right?

If so can it be said that forces propagate at the speed of light whilst what we might think of a tangible particles cannot?

I did post this question on another forum

http://www.thephysicsforum.com/special-general-relativity/7080-massless-particles-inertial-frame-dependent-speed-invariance.html

but didn't get an answer to my last post there...

 

[PeterDonis]

It looks to me like all the massless particles so far discovered may be force bearing particles, there being 3 of them.

Am I right?

Sort of. It's true that, in our current universe, the only particles that are massless (photons, gluons, and gravitons--the last one has not been detected but is believed to exist) are force carriers. However, in the early universe, that was not the case: all of the Standard Model particles were massless. As the universe cooled, a phase transition took place that caused most of the Standard Model particles to acquire mass through their interaction with the Higgs field. So there is no fundamental requirement that massless particles must be force carriers; it just happens to be that way in our universe because of how it evolved.

can it be said that forces propagate at the speed of light whilst what we might think of a tangible particles cannot?

No. First, there are force carriers in our current universe that are not massless--the weak bosons (W+, W-, and Z). Second, as above, what we think of as "tangible particles" were massless in the early universe.

 

[geordief]

thanks a lot.