The claim seems to be that the researchers can make light travel faster than the speed of light.
Is this true? How does it even make sense?
It’s in Nature so presumably there’s something in it, but the claim seems nonsensical to me. What’s going on?
“Researchers develop way to control speed of light, send it backward”, 4 April 2019, University of Central Florida. https://phys.org/news/2019-04-researchers-develop-way-to-control.html
Abouraddy and study co-author Esat Kondakci demonstrated they could speed a pulse of light up to 30 times the speed of light, slow it down to half the speed of light, and also make the pulse travel backward.
Referring to: H. Esat Kondakci et al. Optical space-time wave packets having arbitrary group velocities in free space, Nature Communications (2019). www.nature.com/articles/s41467-019-08735-8
By jointly modulating the spatial and temporal degrees of freedom, arbitrary group velocities are unambiguously observed in free space above or below the speed of light in vacuum, whether in the forward direction propagating away from the source or even traveling backwards towards it.