- #1
jfraze
- 7
- 0
Is it possible to explain how a photon can be a particle yet have no mass? I think I need a scientific clarification either of what a particle is or what mass is.
jfraze said:To define further... Can a photon be "at rest"?
jfraze said:To define further... Can a photon be "at rest"? If a photon could be trapped and held I think that means it would no longer have momentum. Without momentum would it be anything measurable?
Dickfore said:But, these interacting photons become quasiparticles (cavity modes, plasmon polaritons) of a different kind and acquire (rest) mass.
Dickfore said:Furthermore, in condensed matter, lorerentz invariance looses its meaning
And #2 as well. To see why (waveguide) modes acquire rest mass, consider the wave equation, and assume that the transversal cordinate dependence separates from the longitudinal coordinate dependence:PeterDonis said:If you're talking about my #1, yes, I didn't mean to imply that all photons in cavities or other such setups still have zero rest mass. But I can imagine an idealized container where they would.
I'm not sure I would say it "loses its meaning", but I agree things get a lot more complicated.
Dickfore said:It means that the presence of a medium introduces a preferred reference frame (that where the medium is at rest). We no longer require Lorentz invariant expressions as dispersion relations.
Dickfore said:To see why (waveguide) modes acquire rest mass
...
As for the propagation of em waves in a dielectric
PeterDonis said:At this level of modeling, though, we aren't really talking about "photons", are we? (Unless you use "photon" to mean "geometric optics approximation", I guess.) At the quantum level, are these (or the Hamiltonians corresponding to them) the equations that get quantized to determine the spectrum of photon modes?
Dickfore said:I solved the wave equation with a prizmoidal waveguide, and the boundary conditions for the "transversal part" gave rise to discrete eigenvalues [itex]\lambda_n[/itex].
PeterDonis said:So the answer is yes, these *are* the equations that get quantized to determine the spectrum of photon modes. Got it, thanks!
A massless particle is a type of elementary particle that has no mass. This means that it does not have any physical substance or weight.
Yes, massless particles do exist. Examples of massless particles include photons, gluons, and gravitons.
According to Einstein's theory of relativity, mass and energy are equivalent. Therefore, a massless particle may have energy and momentum, but it does not have any physical substance or weight.
Massless particles travel at the speed of light and have no rest mass. They also do not experience time and do not interact with the Higgs field, which is responsible for giving particles their mass.
The existence of massless particles has important implications in the study of physics and cosmology. For example, the behavior of massless particles can help scientists understand the structure of the universe and the nature of light and other electromagnetic radiation.