Scientists can levitate stuff and make it fly around using sound

Japanese scientists have made hundreds of tiny plastic balls float around like miniature spaceships.

Today’s news from the world of Awesome Science comes from the University of Tokyo, where a team has been levitating and controlling objects using sound. Here’s the video:

As the video points out at the beginning, levitation of objects using sound has been around for a few years. If you’ve ever stood in front of a large speaker you’ll know that they can pump out what feels like quite a forceful blast of air as they vibrate - but, somewhat deceptively, that’s not quite the whole story.

Rather than physically push air out from the speaker, what you’re experiencing is a wave of compression moving through the air. The speaker compresses a packet of air, which then “rolls” through the room, with the size of the compressed air corresponding the wavelength of the sound wave. And, just like sound waves, waves that overlap each other create new waves.

To levitate something just requires creating a standing wave. Think of it like this - if you’re watching a sound wave plotted out on a graph, it’ll be rolling along, going up and down as it oscillates. A standing wave occurs when two or more waves combine to create a new wave where, as the wave oscillates, there are points where there’s no movement. They’re called nodes.

Here’s a gif to illustrate how that works. The blue and green waves are combining to create the red wave, which has those points on the central axis that aren’t moving:

(Image: Wikimedia Commons)

If a speaker outputs a standing wave, in the most basic sense it means that it won’t feel like the areas of compression - those blasts of air - are moving. The gaps between those blasts of air will be positions of neutral force, with air pressure pushing in on it from both directions. If you stick an object in there that’s light enough, and smaller that the size the gap (which will be the sound’s wavelength), the force of the air should keep it floating in a stable position.

What the Tokyo University team has done is build upon that idea, by combining sound waves in three dimensions. The video shows not just tiny little plastic balls being levitated and controlled, but also resistors, LEDs, screws, bolts, and other small items. Rhett Allain at Wired worked out that you could levitate anything both smaller than 8mm and less dense than 1,000kg/m3, which is tiny - but it does have practical applications, particularly when people are working with sterile things they want to move but can't touch, like spaceship parts or medicines.

Ian Steadman is a staff science and technology writer at the New Statesman. He is on Twitter as @iansteadman.

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Why did Julian Assange lose his internet connection?

Rumours of paedophilia have obscured the real reason the WikiLeaks founder has been cut off from the internet. 

In the most newsworthy example of "My house, my rules" this year, Julian Assange's dad (the Ecuadorian embassy in London) has cut off his internet because he's been a bad boy. 

Rumours that the WikiLeaks' founder was WiFi-less were confirmed by Ecuador's foreign ministry late last night, which released a statement saying it has "temporarily restricted access to part of its communications systems in its UK Embassy" where Assange has been granted asylum for the last four years. 

Claims that the embassy disconnected Assange because he had sent sexually explicit messages to an eight-year-old girl —first reported by the US political blog Daily Kos — have been quashed. Wikileaks responded by denying the claims on Twitter, as Ecuador explained the move was taken to prevent Assange's interference with the US election. The decision follows the publication of leaked emails from Hillary Clinton's campaign adviser John Podesta, as well as emails from the Democratic National Committee (DNC), by WikiLeaks.

Ecuador "respects the principle of non-intervention in the internal affairs of other states," read the statement, though the embassy have confirmed they will continue to grant Assange asylum. 

Assange first arrived at the Ecuadorian embassy in London in June 2012, after being sought for questioning in Sweden over an allegation of rape, which he denies. WikiLeaks claims this new accusation is a further attempt to frame Assange.  "An unknown entity posing as an internet dating agency prepared an elaborate plot to falsely claim that Julian Assange received US$1M from the Russian government and a second plot to frame him sexually molesting an eight year old girl," reads a news story on the official site.

It is unclear when Assange will be reconnected, although it will presumably be after the US presidential election on 8 November.

Amelia Tait is a technology and digital culture writer at the New Statesman.