nother than a vacum what does light travel the fastest through?

Answer 1

Thru a vacuum is where light travels the fastest.

See:http://www.madsci.org/posts/archives/may98/893732585.Ph.r.html

When a light wave enters matter, the light wave's electric field
causes charged particles in the matter to accelerate back and
forth. That's because an electric field exerts forces on charged
particles. The light wave gives up some of its energy to these charged
particles and is partially absorbed in the process. However, the
charged particles don't retain the light's energy very long. They are
accelerating and accelerating charged particles emit electromagnetic
waves. In fact, they reemit the very same light wave that they
absorbed moments earlier. Overall, the light wave is partially
absorbed and then reemitted by each electrically charged particle it
encounters, so that the light continues on its way as though nothing
had happened.

However, something has happened--the light wave has been delayed
ever so slightly. This absorption and reemission process holds the
light wave back so that it travels at less than its full speed. If the
charged particles in the matter are few and far between, this slowing
effect is almost insignificant. But in dense materials such as glass
or diamond, the light wave can be slowed substantially.

Answer 2

Nothing can travel faster than the speed of light. Not even light itself.

Answer 3

light speed is set and can never change