Today, you might read that scientists have developed a way to produce faster-than-light travel. But steady, there: we've been burnt once recently, so let's not let it happen again. Did scientists really manage to break the speed of light?

According to Einstein's special theory of relativity, light traveling in a vacuum is the universal speed limit. That's a well-established ruleâ€”but it is one that scientists like to flirt with the idea of breaking.

### Faster Than Light...

That group includes researchers at the US National Institute of Standards and Technology (NIST), who have been trying to exploit a loophole in the rule, that could see something travel faster than light. That thing is information, and the loophole relies on forcing one pulse to propagate through a second one. If the second pulse is moving at a speed close to the speed of light, it should in theory be possible to make the first one travel faster than the speed of light.

Which is, pretty much, exactly what the researchers from NIST have done, if you read their paper in Physical Review Letters. They've taken that conceptâ€”which is itself old and done before, but so badly that the results were really rather scrappyâ€”and given it another go.

The NIST scientists used a concept called four-wave mixing. That sounds complex, but it's really just a way of combining signals of different frequencies in such a way as to produce a new signal containing four separate frequencies. In fact, they took 200-nanosecond-long "seed" pulses of laser light and aimed them into a heated cell containing rubidium vapor. Then, they pumped in a second beam at a different frequency. The two beams interacted with each other, and the vapor, to produce a new pulse which itself contained a second, moving pulse. Their results suggest that the pulse-within-a-pulse went faster the speed of light. Great!

### ...But Besides the Point

Wait, no. Not that great. The pulse is incredibly short-livedâ€”it takes next to no time for it to propagate the length of its carrier pulseâ€”and it can never really do anything. It starts, then stops. In fact, it's little more than a little mathematical trick. What the scientists are observing here is the propagation of a small scrap of informationâ€”so nothing with any matterâ€”moving slightly faster than the speed of light.