Faster than Light Particles: Meuons & Photons

[vivekhere]

Can anyone help on it?

hi,

is any particle can travel faster than light ?? . somewhere i heard meuons,photons can travel. is it so??

 

[HallsofIvy]

You have, actually, two questions here. Certainly, photons travel at the speed of light, not faster. Photons are light. Muon's, I believe, according to some theories have zero rest mass and so could travel at the speed of light, not faster. Relativity says that no object can go from below the speed of light to greater than the speed of light but leaves open the possibility of "tachyons" that always travel faster than light. No such particles have ever been observed.

 

[ZapperZ]

hi,

is any particle can travel faster than light ?? . somewhere i heard meuons,photons can travel. is it so??

No, they can't.

Again, whenever you "hear" something like this, REMEMBER the source and then make the exact citation here. There's no way of telling if (i) you heard the wrong information (ii) you interpret the information wrongly (iii) or there's just some bad physics going on.

Zz.

 

[ZapperZ]

Muon's, I believe, according to some theories have zero rest mass and so could travel at the speed of light, not faster.

Er.. muons do have a mass, larger than electrons, in fact. I think you may be thinking of neutrinos.

Zz.

 

[Danger]

There's also the ever-vexing issue of group velocity. While individual photons always travel at c, the transmission of a light signal through a refractive medium can be delayed enough to allow other particles to overtake it (see the Cherenkov Radiation thread below).

 

[wxrocks]

Ken Salem wrote a book ("2.8 Angstroms") that theorizes the speed of light is changing and is relative to our position in the universe. So I suppose using this theory, particles could travel faster than the speed of light according to us.

It is an interesting book -- a little far fetched, but very interesting.