There was a young fellow called Bright…: “Because the jump would be sudden, it could not be predicted by observing the leading edge of the pulse. In other words, it might be used to convey information at superluminal velocities. But nature seems to have thought of that one. The group’s latest experiment, which Dr Gauthier told the conference about, showed that the jump is not accelerated in the same way that a smooth crest is, but travels only at c. The details of why the jump causes the pulse to slow down are not well understood.”