Nothing, not even and including Light

[Quietus]

What's the difference between travelling backwards and changing the direction when reflected? Their mirror analogy doesn't explain anything to me.

They were saying if you fire a 'pulse of light' into a fiber optic cable, as the 'pulse' enters the cable, two pulses are instantly propagated at the other end (one moving forward, another moving backward).

Hence the 'pulse' moving forward meant it travelled faster than light. The other 'pulse' moves backward from the other end as well.

The mirror and 'special materials' were only examples of light slowing down and different speeds in a medium.

The difference is when light is reflected it is 'travelling' the whole length with speed respective to the medium. In their example the light instantly appeared at the other end (forward and backward).

What I don't know understand is what's the difference between the 'pulse of light' and a laser. I know what a laser is.

As the pulse exited the laser, it was split into two

[Avicenna]

A pulse could be in all directions I guess, being just normal light. Radiated, so that not all is travelling in the same direction. If you use a laser, it's all going to go in one direction.

Just an idea, it's probably wrong.