Scientists Make Light Travel At Slower Speed

A team of scientists has managed to slow the speed of light. The photons - particle representing a quantum of light - reached the "finishing line" at different times.

Researchers made this feat possible by sending photos through a special mask that changed photon's shape and slowed them to less than light speed. Even more interestingly, the photons remained traveling at the lower speed even when they returned to free space.

Light travels at 186,282 miles per second in free space. It travels slower when passing through medium like water or glass, but it comes back to higher velocity as soon as it returns to free space.

Researchers built "racetrack" for photons and made them race in pairs. One photon was left in normal state and the other was sent through a special mask. They noted that the mask forces the photon to change its shape and travel slower than the speed of light.

"After the mask, the photon is launched into a sort of racetrack about a meter in length," explained Dr Jacquiline Romero of Glasgow university, according to BBC.

"Then we take the time in which the unshaped photon finishes the racetrack, and the shaped photon's time as well, and then compare the two times."

Not by much - a few millionths of a metre - but it showed that it had not just been slowed by the mask, but had continued to travel at less than light speed even after it had returned to free space, BBC added.

The experiment could alter the way science looks at light.

The findings of the study were published in the journal Science Express.