Science fiction is filled with tractor beams, and real researchers have been working on making it fact. And we’re getting closer with a new acoustic tractor beam that has lifted the largest ever object: a 2-cm ball. In the movies, tractor beams are beams of some undefined energy, but that’s not the case. Commonly, researchers use sound.
The idea of harnessing sound waves for levitation isn’t new. Scientists have been exploiting the properties of air and sound to this end for a while. Remember that air is a fluid that behaves like a liquid, even if we can’t see or feel it the same way. Similarly, sound is a physical vibration, even if we don’t think of it as such.
Harnessing acoustic power is harnessing the lifting effect of physical sound waves as they move through the air. The sound compresses the air in waves and those waves correspond to the sound’s wavelength. Acoustic levitation uses this wave to balance against gravity.
The result is a free-floating particle that looks a little like science fiction magic. Dialing in the sound waves means lifting objects with extreme precision, but it isn't easy technology to scale up.