Forget superconductors and magnetic fields. Scientists from the University of Tokyo have developed a way to use sound waves to levitate objects and move them around midair.
When a sound wave travels through air, it compresses air molecules as it rolls along its way. It creates a wave of pressure as it travels from a speaker through a room. One sound wave just vibrates forward through the air, but if you hit one sound wave with another travelling in the opposite direction, the two waves can combine and create a standing wave. This standing wave has points along it where the air compression is travelling in opposite directions and slam into each other creating points called nodes.
So to levitate an object, the researchers created a standing wave and dropped the object between those opposite directions of air pressure. The currents coming from opposite directions will hold the object in midair at the node of the wave, like in the image below:
Sadly, this does not mean we’re about to have hoverboards; if you look at the equation of the wave and do the maths, the setup can only support very small and very light objects. Also, these sound waves have to be finely tuned to hover and move the object.
Scientists have been able to levitate small objects using sound waves for a few years now, but now the researchers have shown that they can actually move the objects around in three dimensional space instead of simply hovering it in a stationary position.
The group of scientists from Tokyo University developed a way to control the sound waves and actually move the nodes of the wave around, moving the small objects with them. It really looks like magic:
The particles are manipulated using speakers that send two sound waves at each other from opposite directions.
The speakers actually do not produce any noise — at least not at the pitch that the human ear can hear. In the GIF below you can actually see what the standing wave looks like as the scientists levitate a piece of dry ice. The white gas flowing off the ice shows where the waves are:
The scientists can even just toss these small balls onto the standing wave and have them float there — you can see below that some of them get trapped in the nodes of the wave on their way down.
The details of the experiment are published in the open access pre-publication database arVix. You can watch the entire video below.
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