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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Chinese loan sharks are using nudes as collateral. Is this the grim future of revenge porn?

The economics of shame. 

When female students in Guangdong, a southern province in China, applied for a small loan, they were met with a very specific demand. Send naked photos of yourself holding your ID cards, they were told – or you won’t get the money. If you don’t pay up, we’ll make the photos public.

This is according to Nandu Daily, the area’s local newspaper, but has also been reported by the Associated Press and the Financial Times. The FT places the trend in the context of the Chinese economy, where peer to peer lending sites like Jiedaibao, the platform where the students allegedly contacted the lenders, are common. Thanks to the country’s slowing economy, the paper argues, lenders are increasingly intent on making sure they’ll be repaid.

As a result, there have also been reports of property destruction and even beatings by loan sharks. Part of the problem is that these are unregulated lenders who operate through an online platform. In this case, Jiedaibao says the agreement about photos was made via different communication channels, and told the FT: “This is an illegal offline trade between victims and lenders who did it by making use of the platform.” 

This new use of naked photos in this case, though, plays to the ways that shame is now used as a weapon, especially online – and the fact that it can essentially be monetised.

Revenge porn is a huge and growing problem. As Jon Ronson noted in his book, So You’ve Been Publicly Shamed, the internet offers a unique space in which shamings (over a naked photo, or an unwise comment) can be transmitted all over the world almost instantly. For some, this threat is simply too much to cope with, as it was for the growing number teenagers who have committed suicide after being blackmailed with naked photos

It’s telling, too, that the students targeted with these demands were, reportedly at least, women. Most victims of revenge porn are also women. The shame brought down on women who appear in these photos is not so much about their nakedness, but the implication that they've behaved in a sexual way. In China, virginity is still highly valued in marriage, and your family and friends would likely take the spread of naked photos of you extremely seriously. In Behind the Red Door, Sex in China , Richard Burger notes:

Every year, thousands of Chinese women pay for an operation to restore their hymens shortly before their wedding so that husbands can see blood on the sheets on their honeymoon night.

The strange story of these students and their loans highlights two important points. First, as anti-loan shark campaigners have argued for decades, “free choice” in signing up to extortionate fees or demands when taking out a loan is a misnomer when you’re constrained by economic need and desperation.

But second, we can’t allow the shame around female sexuality to become a commodity. We need to both protect women's rights and persecute those who share images without consent, but also fight the stigma that makes these shamings possible in the first place. It's not acceptable that the suggestion of sexual activity can still be used to ruin women's lives.

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.