Scientists drag light by slowing it to speed of sound

Scientists drag light by slowing it to speed of sound
(PhysOrg.com) -- Scientists at the University of Glasgow have, for the first time, been able to drag light by slowing it down to the speed of sound and sending it through a rotating crystal.

"Most people may think the speed of light is constant, but this is only the case in a vacuum, such as space, where it travels at 671million mph.

[...] when it travels through different substances, such as water or solids, its speed is reduced, with different wavelengths (colours) travelling at different speeds.

[...] that light can be dragged when it travels through a moving substance, such as glass, air or water [...]

Once the light enters the ruby, its speed is slowed down to around the speed of sound (approximately 741mph) and the spinning motion of the rod drags the light with it, resulting in the image being rotated by almost five degrees: large enough to see with the naked eye."

in PhysOrg.com