Speed of light slowed

http://www.msn.com/en-us/news/technology/scientists-slow-the-speed-of-light/ar-AA8uQjo?ocid=ansBBCNews11

I read the article this morning. What they are measuring is not really the speed of light in a vacuum. Media are overselling it a bit, as usual. Still, it's a nice experiment.

But they measured the speed of the photons in a mask, and when they switched it back to a vacuum, the speed remained the same as it was in the mask. That's significant.

Originally posted by blunderdog
But they measured the speed of the photons in a mask, and when they switched it back to a vacuum, the speed remained the same as it was in the mask. That's significant.

Originally posted by twhitehead
The article was very unclear about what exactly they did. It would be nice to know what the quantum mechanics of this is, but then quantum mechanics never does translate well into macroscopic analogies.

Originally posted by KazetNagorra
Basically what they do is some tricks with the geometry to ensure that the light no longer propagates as a plane wave. They then show that this different wave travels at a different speed through a vacuum.

Originally posted by KazetNagorra
I read the article this morning. What they are measuring is not really the speed of light in a vacuum. Media are overselling it a bit, as usual. Still, it's a nice experiment.

Originally posted by DeepThought
Is it on ArXiv.org? I tried a couple of search terms but couldn't find it.

Originally posted by KazetNagorra
I read it on Science Express, but there is also an arXiv version:

http://arxiv.org/abs/1411.3987

To slow down a photon, well, that's one thing.

But come back when you have sped up a photon to FTL-velocities. That would be really something!

How is being oversold? Just by reporting it? Maybe if they used notations like a chess game, with exclams it would be overselling. Otherwise, it's just straightforward reporting.