Tractor Beam Levitates Large Orbs with Sound

[Judi Lynn]

By Stephanie Pappas, Live Science Contributor | January 24, 2018 07:18am ET

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. [Science Fact or Fiction? The Plausibility of 10 Sci-Fi Concepts]

Splitting force and momentum
Levitating objects with sound is not new, but the size of the objects has long been limited: the object being levitated could not be larger than the wavelength of the sound waves holding it up. This was true even in one of the strongest sources of levitation from a single source of sound waves, acoustic vortices. Imagine a tornado of rushing wind with a quiet spot in its center; the same funnel shape can be formed with sound waves. The problem, Caleap told Live Science, is that the waves transfer some of their rotational forces onto the object sitting in the quiet spot.

More:
https://www.livescience.com/61512-tractor-beam-levitates-objects.html?utm_source=notification

[eppur_se_muova]

1. To nitpick,is this really a "tractor" beam or a repulsor ?

i.e. can it pull, rather than push ?