Index Key:  PHY080
Author:     ztlifb
Subject:    Speed limit of light
Text:       What keeps light from going any faster?

Response #:  1 of 1
Author:      Arthur Smith
Text:        Well, as best as I can explain it, the speed of light is a 
fundamental physical limitation, which no particle can exceed.  It is kind of 
built into the structure of space and time in our universe.  Any particle with 
no mass, by the way, will always move at the speed of light, so it is not just 
light that does it.  Actually, in physical materials, light actually moves a 
little slower than the "speed of light".  This is measured by the index of 
refraction of the material, and the reason is because light interacts with the 
electrons and other charged particles in the materials, which has the overall 
effect of slowing it down (as well as reflecting, and sometimes absorbing, the 
light).