For the first time ever, scientists have slowed down the speed of light – particles known as photons – as it traveled through free space, a study says.
Scientists successfully reduced the speed of photon particles as they traveled in free space after passing through a special mask, researchers from the University of Glasgow and Heriot-Watt University, both in Scotland, said in a paper published in Science Express on Friday.
The effect was achieved by applying the mask to a beam of light to give photons a spatial structure, the researchers said.
They discovered that the mask placed a limit on the top speed at which the photons can travel once they pass through the mask.
The effect of passing the light through the mask is very different to the slowing effect of passing light through a medium like glass or water, whereby the particle returns to the speed of light once it exits the medium, the scientists explained.
“This finding shows unambiguously that the propagation of light can be slowed below the commonly accepted figure of 299,792,458 meters per second (186,282 miles per second), even when travelling in air or vacuum,” said one of the lead authors of the paper, Jacquiline Romero.
The principle can be applied to essentially any wave theory, including sound waves, the paper said.
“The results give us a new way to think about the properties of light and we’re keen to continue exploring the potential of this discovery in future applications,” concluded Professor Miles Padgett, team lead from the University of Glasgow’s Optics Group.