What distinguishes photons from other particles in terms of mass and speed?

[imi]

If light consists of particles, moving at a certain speed and having a certain mass that our eyes can detect, what makes it so much different than other detectable particles moving at other speeds with different masses detectable with other devices?


Are there particles that would be considered light if they were moving at the needed rate to cause a reaction but are not called light because they are moving too slowly? Are there particles just floaing around, not causing reactions because of their relative velocity and not detectable?

 

[kuenmao]

Because if light were not moving, they would have no mass. That's why it is so special.
In technical terms, we call that "no rest mass". This is a consequence of special relativity.

 

[jcsd]

The two main differences between a photon and an electron and nucleons (i.e. the stuff we're made of are:

1) photons have no mass

2) the speed of a photon is invariant under a lorentz transformation (i.e. photons always travel at c), this follows on from (1.

Of course there are other particles that also have no mass (and hence also always travel at c).