A little plot bunny offered with love to all our sci fi writers:
A new “tractor beam” can levitate large objects in midair, using only sound.
So far, researchers have floated spheres as large as 0.6 inches (16 millimeters) in diameter and moved orbs as large as 0.8 inches (2 cm) on a tabletop using tornadoes of sound waves. Theoretically, vortices made by an array of 200 speakers by 200 speakers could hold up objects as large as 31 inches (80 cm) in diameter.
“This is new to acoustics,” said study co-author Mihai Caleap, a senior research associate in engineering at the University of Bristol in England.