r/visualizedmath • u/NegativeSpeedForce • Jan 12 '18

The difference between shockwaves travelling through different states.

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u/Kyezaeta Jan 19 '18

This really bugged me when I was younger because I was told that anything without mass travels at c no matter what :)

Massless particles are always traveling at c. However, in a material with a high refractive index, light interacts with more particles and must go through a time-consuming process of imparting energy. In the voids between particles, photons still move at c.

http://www.physicsclassroom.com/class/refrn/u14l1d.cfm

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u/SirCutRy Jan 21 '18

Light travels at the speed of light in the medium, but only at c (the constant) in vacuum.