Light can behave in very unexpected ways when you squeeze it into small spaces. In a paper in the journal Science, Mark ...

Longitudinal waves are also known as compression waves, and that’s what sound waves are. There’s no perpendicular motion to these, rather, the wave moves in the same direction as the disturbance.

To get an idea of why making things spin with sound waves is difficult, picture a tube that holds a turbine. Normally, to make the turbine spin, a fluid would flow past the blades of the turbine.

Researchers at ETH Zurich have managed to make sound waves travel only in one direction. In the future, this method could also be used in technical applications with electromagnetic waves.