Scientists Slow the Speed of Light

lightbox32 sends news that scientists have found a way to slow individual photons within a beam of light. Their work was published today in Science Express (abstract, pre-print). The researchers liken a light beam to a team of cyclists — while the group as a whole moves at a constant speed, individual riders may occasionally drop back or move forward. They decided to focus on the individual photons, rather than measuring the beam as a whole. The researchers imposed a particular pattern on a photon, then raced it against another photon, and found that the two arrived at their destination at slightly different times. The work demonstrates that, after passing the light beam through a mask, photons move more slowly through space. Crucially, this is very different to the slowing effect of passing light through a medium such as glass or water, where the light is only slowed during the time it is passing through the material—it returns to the speed of light after it comes out the other side. The effect of passing the light through the mask is to limit the top speed at which the photons can travel.

Comments

But then don't some have to go FASTER than light?

[Anonymous Coward]

Not a physicist, but a cyclist and an engineer--

If the population travels as 'c' on average, and they have proven that some photons slow down... Doesn't that mean other photons MUST be traveling faster than c? My impression is the relativity has no bearing here--by traveling at 'c' they are already breaking that equation. The peloton works because some move back while others move up. This blurb seems to only discuss the "back" part.

Re:Really Neat

[Orgasmatron]

My first thought is that this is based on information.

** Crackpot speculation alert **

c seems to be a limitation on the speed of information more than anything else. When a random photon comes in, the information arrives at the same time as the photon. If the photon has been selected in some way that allows you to make predictions, the information would arrive slightly early. To prevent this, the photons need to slow down so that the early information doesn't arrive before it should.