How can we see light moving with us if its speed is reduced by a factor of 100?

[Bigee]

I know that the speed of light cannot be attained in vacuum as by the time of reaching there, mass increases excessively, causing whatever energy we had initially to be taken up by it. But what if the material in which light is moving is so optically dense that speed of light is reduced by a factor of ,say about 100, would it then be possible to move alongside it and actually see light moving with us... given that our mass is very small and we can see.

 

[Hootenanny]

Welcome to PF Bigee,

It is indeed possible for a particle in a medium to travel faster than light does in the same medium. When this occurs a phenomenon known as http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/cherenkov.html" is observed, which analagous to the sonic boom obeserved when an object travels faster than the speed of sound in air.