In what can only be described as a breakthrough, a team of scientists from the University of Glasgow and Heriot-Watt University have, for the first time ever, slowed down the speed of light travelling through air. This finding shows unambiguously that the propagation of light can be slowed below the commonly accepted figure of 299,792,458 metres per second, even when travelling in air or vacuum. The team, members of the Scottish Universities Physics Alliance, have published their results in the journal Science Express.
To achieve this, the researchers sent photons – individual particles of light – through a special mask. It changed the photons’ shape – and slowed them to less than light speed. The photons remained travelling at the lower speed even when they returned to free space.
The speed of light has previously been regarded as an absolute. It propagates more slowly when passing through materials like water or glass but goes back to its higher velocity as soon as it returns to free space again.
The experiment is likely to alter how science looks at light.
