I was bothered by the same thing. But the whole thing looks garbled. Most science reporting in the mainstream press is terrible because reporters don't know any science and their editors don't care. Explaining physics to non-scientists is hard enough for those who do know it. Most people just pretend to explain by stating facts and theories and glossing over the actual logic, which requires more math.

I have a feeling that they are saying that it is the signal (a pulse of a certain shape) that is traveling extra fast, and not the medium (the light). Dispersion, by definition, is the changing shape of a pulse (or other signal) made of constituent waves of different wavelengths that are propagating in a medium that carries the different wavelengths at different speeds. Perhaps the upcoming article in Nature will explain properly how the pulse gets to the other side of the cesium tube so fast and then gets its shape back.

>I'm no scientist, but this isn't making sense to me...
>
>It takes 0.2 nanoseconds through a vacuum, but through their chamber, it taks 62 nanoseconds _less_ than that? So it takes -61.8 nanoseconds? What am I missing?
>
>Thanks,
>
>Michelle
>
>
>>Folks,
>>
>>Thought you might find this interesting: http://biz.yahoo.com/prnews/000719/nj_nec_sup.html
>>
>>Best,
>>
>>DD