Scientists drag light by 5° by slowing to the speed of sound
By slowing a beam of light down to the speed of sound, UK researchers have dragged photons by an unprecedented 5°, proving a longstanding theory of physics and opening up potential applications in quantum data storage.
The speed of light is constant in a vacuum, such as space, where it travels at 671 million miles per hour.
When it travels through different substances, such as water or solids, its speed is reduced, with different wavelengths (colours) travelling at different speeds.
In addition, light can be dragged when it travels through a moving substance such as glass, air or water — a phenomenon first predicted by Augustin-Jean Fresnel in 1818.
Indeed, spinning a pane of glass as fast as possible is predicted to rotate the image of the world behind it slightly, but this rotation would be about a millionth of a degree and imperceptible to the human eye.
In an effort to understand the phenomenon in more detail, a team from Glasgow University tried to increase the rotational dragging effect, as Dr Sonja Franke-Arnold explained to The Engineer.
‘We were looking at this dragging effect for some time but couldn’t resolve rotation by more than a micro-degree — so small you can’t even measure it properly.
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