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.

John Moore
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The man who created the fake Tube sign explains why he did it

"We need to consider the fact that fake news isn't always fake news at the source," says John Moore.

"I wrote that at 8 o'clock on the evening and before midday the next day it had been read out in the Houses of Parliament."

John Moore, a 44-year-old doctor from Windsor, is describing the whirlwind process by which his social media response to Wednesday's Westminster attack became national news.

Moore used a Tube-sign generator on the evening after the attack to create a sign on a TfL Service Announcement board that read: "All terrorists are politely reminded that THIS IS LONDON and whatever you do to us we will drink tea and jolly well carry on thank you." Within three hours, it had just fifty shares. By the morning, it had accumulated 200. Yet by the afternoon, over 30,000 people had shared Moore's post, which was then read aloud on BBC Radio 4 and called a "wonderful tribute" by prime minister Theresa May, who at the time believed it was a genuine Underground sign. 

"I think you have to be very mindful of how powerful the internet is," says Moore, whose viral post was quickly debunked by social media users and then national newspapers such as the Guardian and the Sun. On Thursday, the online world split into two camps: those spreading the word that the sign was "fake news" and urging people not to share it, and those who said that it didn't matter that it was fake - the sentiment was what was important. 

Moore agrees with the latter camp. "I never claimed it was a real tube sign, I never claimed that at all," he says. "In my opinion the only fake news about that sign is that it has been reported as fake news. It was literally just how I was feeling at the time."

Moore was motivated to create and post the sign when he was struck by the "very British response" to the Westminster attack. "There was no sort of knee-jerk Islamaphobia, there was no dramatisation, it was all pretty much, I thought, very calm reporting," he says. "So my initial thought at the time was just a bit of pride in how London had reacted really." Though he saw other, real Tube signs online, he wanted to create his own in order to create a tribute that specifically epitomised the "very London" response. 

Yet though Moore insists he never claimed the sign was real, his caption on the image - which now has 100,800 shares - is arguably misleading. "Quintessentially British..." Moore wrote on his Facebook post, and agrees now that this was ambiguous. "It was meant to relate to the reaction that I saw in London in that day which I just thought was very calm and measured. What the sign was trying to do was capture the spirit I'd seen, so that's what I was actually talking about."

Not only did Moore not mean to mislead, he is actually shocked that anyone thought the sign was real. 

"I'm reasonably digitally savvy and I was extremely shocked that anyone thought it was real," he says, explaining that he thought everyone would be able to spot a fake after a "You ain't no muslim bruv" sign went viral after the Leytonstone Tube attack in 2015. "I thought this is an internet meme that people know isn't true and it's fine to do because this is a digital thing in a digital world."

Yet despite his intentions, Moore's sign has become the centre of debate about whether "nice" fake news is as problematic as that which was notoriously spread during the 2016 United States Presidential elections. Though Moore can understand this perspective, he ultimately feels as though the sentiment behind the sign makes it acceptable. 

"I use the word fake in inverted commas because I think fake implies the intention to deceive and there wasn't [any]... I think if the sentiment is ok then I think it is ok. I think if you were trying to be divisive and you were trying to stir up controversy or influence people's behaviour then perhaps I wouldn't have chosen that forum but I think when you're only expressing your own emotion, I think it's ok.

"The fact that it became so-called fake news was down to other people's interpretation and not down to the actual intention... So in many interesting ways you can see that fake news doesn't even have to originate from the source of the news."

Though Moore was initially "extremely shocked" at the reponse to his post, he says that on reflection he is "pretty proud". 

"I'm glad that other people, even the powers that be, found it an appropriate phrase to use," he says. "I also think social media is often denigrated as a source of evil and bad things in the world, but on occasion I think it can be used for very positive things. I think the vast majority of people who shared my post and liked my post have actually found the phrase and the sentiment useful to them, so I think we have to give social media a fair judgement at times and respect the fact it can be a source for good."

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