# 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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# Marcus Hutchins: What we know so far about the arrest of the hero hacker

The 23-year old who stopped the WannaCry malware which attacked the NHS has been arrested in the US.

In May, Marcus Hutchins - who goes by the online name Malware Tech - became a national hero after "accidentally" discovering a way to stop the WannaCry virus that had paralysed parts of the NHS.

Now, the 23-year-old darling of cyber security is facing charges of cyber crime following a bizarre turn of events that have left many baffled. So what do we know about his indictment?

Arrest

Hutchins, from Ilfracombe in Devon, was reportedly arrested by the FBI in Las Vegas on Wednesday before travelling back from cyber security conferences Black Hat and Def Con.

He is now due to appear in court in Las Vegas later today after being accused of involvement with a piece of malware used to access people's bank accounts.

"Marcus Hutchins... a citizen and resident of the United Kingdom, was arrested in the United States on 2 August, 2017, in Las Vegas, Nevada, after a grand jury in the Eastern District of Wisconsin returned a six-count indictment against Hutchins for his role in creating and distributing the Kronos banking Trojan," said the US Department of Justice.

"The charges against Hutchins, and for which he was arrested, relate to alleged conduct that occurred between in or around July 2014 and July 2015."

His court appearance comes after he was arraigned in Las Vegas yesterday. He made no statement beyond a series of one-word answers to basic questions from the judge, the Guardian reports. A public defender said Hutchins had no criminal history and had previously cooperated with federal authorities.

The malware

Kronos, a so-called Trojan, is a kind of malware that disguises itself as legitimate software while harvesting unsuspecting victims' online banking login details and other financial data.

It emerged in July 2014 on a Russian underground forum, where it was advertised for \$7,000 (£5,330), a relatively high figure at the time, according to the BBC.

Shortly after it made the news, a video demonstrating the malware was posted to YouTube allegedly by Hutchins' co-defendant, who has not been named. Hutchins later tweeted: "Anyone got a kronos sample."

His mum, Janet Hutchins, told the Press Association it is "hugely unlikely" he was involved because he spent "enormous amounts of time" fighting attacks.

Research?

Meanwhile Ryan Kalember, a security researcher from Proofpoint, told the Guardian that the actions of researchers investigating malware may sometimes look criminal.

“This could very easily be the FBI mistaking legitimate research activity with being in control of Kronos infrastructure," said Kalember. "Lots of researchers like to log in to crimeware tools and interfaces and play around.”

The indictment alleges that Hutchins created and sold Kronos on internet forums including the AlphaBay dark web market, which was shut down last month.

"Sometimes you have to at least pretend to be selling something interesting to get people to trust you,” added Kalember. “It’s not an uncommon thing for researchers to do and I don’t know if the FBI could tell the difference.”

It's a sentiment echoed by US cyber-attorney Tor Ekeland, who told Radio 4's Today Programme: "I can think of a number of examples of legitimate software that would potentially be a felony under this theory of prosecution."

Hutchins could face 40 years in jail if found guilty, Ekelend said, but he added that no victims had been named.

This article also appears on NS Tech, a new division of the New Statesman focusing on the intersection of technology and politics.

Oscar Williams is editor of the NewStatesman's sister site NSTech.