# 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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# Extremist ads and LGBT videos: do we want YouTube to be a censor, or not?

Is the video-sharing platform a morally irresponsible slacker for putting ads next to extremist content - or an evil, tyrannical censor for restricting access to LGBT videos?

YouTube is having a bad week. The Google-owned video-sharing platform has hit the headlines twice over complaints that it 1) is not censoring things enough, and 2) is censoring things too much.

On the one hand, big brands including Marks & Spencer, HSBC, and RBS have suspended their advertisements from the site after a Times investigation found ads from leading companies – and even the UK government – were shown alongside extremist videos. On the other, YouTubers are tweeting #YouTubeIsOverParty after it emerged that YouTube’s “restricted mode” (an opt-in setting that filters out “potentially objectionable content”) removes content with LGBT themes.

This isn’t the first time we’ve seen a social media giant be criticised for being a lax, morally irresponsible slacker and an evil, tyrannical censor and in the same week. Last month, Facebook were criticised for both failing to remove a group called “hot xxxx schoolgirls” and for removing a nude oil painting by an acclaimed artist.

That is not to say these things are equivalent. Quite obviously child abuse imagery is more troubling than a nude oil painting, and videos entitled “Jewish People Admit Organising White Genocide” are endlessly more problematic than those called “GAY flag and me petting my cat” (a highly important piece of content). I am not trying to claim that ~everything is relative~ and ~everyone deserves a voice~. Content that breaks the law must be removed and LGBT content must not. Yet these conflicting stories highlight the same underlying problem: it is a very bad idea to trust a large multibillion pound company to be the arbiter of what is or isn’t acceptable.

This isn’t because YouTube have some strange agenda where it can’t get enough of extremists and hate the LGBT community. In reality, the company’s “restricted mode” also affects Paul Joseph Watson, a controversial YouTuber whose pro-Trump conspiracy theory content includes videos titled “Islam is NOT a Religion of Peace” and “A Vote For Hillary is a Vote For World War 3”, as well as an interview entitled “Chuck Johnson: Muslim Migrants Will Cause Collapse of Europe”. The issue is that if YouTube did have this agenda, it would have complete control over what it wanted the world to see – and not only are we are willingly handing them this power, we are begging them to use it.

Moral panics are the most common justification for extreme censorship and surveillance methods. “Catching terrorists” and “stopping child abusers” are two of the greatest arguments for the dystopian surveillance measures in Theresa May’s Investigatory Powers Act and Digital Economy Bill. Yet in reality, last month the FBI let a child pornographer go free because they didn’t want to tell a court the surveillance methods they used to catch him. This begs the question: what is the surveillance really for? The same is true of censorship. When we insist that YouTube stop this and that, we are asking it to take complete control – why do we trust that this will reflect our own moral sensibilities? Why do we think it won't use this for its own benefit?

Obviously extremist content needs to be removed from YouTube, but why should YouTube be the one to do it? If a book publisher released A Very Racist Book For Racists, we wouldn’t trust them to pull it off the shelves themselves. We have laws (such as the Racial and Religious Hatred Act) that ban hate speech, and we have law enforcement bodies to impose them. On the whole, we don’t trust giant commercial companies to rule over what it is and isn’t acceptable to say, because oh, hello, yes, dystopia.

In the past, public speech was made up of hundreds of book publishers, TV stations, film-makers, and pamphleteers, and no one person or company had the power to censor everything. A book that didn’t fly at one publisher could go to another, and a documentary that the BBC didn’t like could find a home on Channel 4. Why are we happy for essentially two companies – Facebook and Google – to take this power? Why are we demanding that they use it? Why are we giving them justification to use it more, and more, and more?

In response to last week’s criticism about extremist videos on the YouTube, Google UK managing director Ronan Harris said that in 2016 Google removed nearly 2 billion ads, banned over 100,000 publishers, and prevented ads from showing on over 300 million YouTube videos. We are supposed to consider this a good thing. Why? We don't know what these adverts were for. We don't know if they were actually offensive. We don't know why they were banned.

As it happens, YouTube has responded well to the criticism. In a statement yesterday, Google's EMEA President, Matt Brittin, apologised to advertisers and promised improvements, and in a blog this morning, Google said it is already "ramping up changes". A YouTube spokesperson also tweeted that the platform is "looking into" concerns about LGBT content being restricted. But people want more. The Guardian reported that Brittin declined three times to answer whether Google would go beyond allowing users to flag offensive material. Setting aside Brexit, wouldn't you rather it was up to us as a collective to flag offensive content and come together to make these decisions? Why is it preferable that one company takes a job that was previously trusted to the government?