Physicists Have Broken the Speed of Light with Pulses Inside Hot Plasma

sciencealert.com

7 pointsddingus4 comments

All I want to know when confronted with a headline like this is: FTL info transmission or not? I can’t discern the answer from the article. So I’ll assume as always there’s some gotcha that means it’s a no.

> FTL info transmission or not?

No.

It's about group velocity https://en.wikipedia.org/wiki/Group_velocity

In some experiments it's easier to make the calculations using fake waves that move at a velocity that may be faster than light, but they are just a mathematical recombination of waves that move at another velocity (that is less or equal than light velocity).

Thanks, this answers my question.

Quick thought: does this open the door somehow to measure the speed of light to test whether it is the same on return path vs travel path?

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