Researchers from Brazil and the UK have been able to levitate a 50-mm (2-in) solid polystyrene sphere using acoustic waves. These waves have been used before to levitate objects. However, they did have a threshold. The objects’ size, at most, was a quarter of the wavelength of an acoustic wave. This is also the first spherical object levitated acoustically; the earlier objects were wire-like or planar in shape. For the types of waves the researchers are using, ultrasound waves with a frequency above 20 kHz, the maximum size should be at 4mm.