# 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.

Photo: Getty/New Statesman
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# The mother lode: how mums became the ultimate viral fodder

The internet’s favourite joke used to be "your mum". Now it's "my mum".

“I was like: oh my.”

Terri Squires is describing her reaction to the news that she had gone viral. Last month, more than 213,000 people shared a tweet about Terri – but it wasn’t sent from her account. The 50-year-old Ohioan was propelled to internet stardom by her son, Jeff, who had tweeted about his mother.

“I didn’t really realise what it meant at first until he was like: ‘Mum, you do realise that millions of people have looked at this?’ … When I started seeing those numbers I was like: ‘Oh boy’.”

It’s a funny story – and Terri laughs heartily all she tells it. After coming out of a meeting, she checked her phone and noticed a picture of a missing – white – dog on Facebook. She quickly texted 17-year-old Jeff to check that the family dog, Duey, was safe. “That’s not Duey… Duey’s face is brown,” replied her son. “OK – just checking,” replied Terri.

More than 600,000 people “liked” Terri’s mistake after Jeff shared screenshots of the text message exchange on Twitter. But Terri is just one of hundreds of mums who have gone viral via their sons and daughters. Texts mums send, mistakes they make, things they fail to notice – these have all become the ultimate viral fodder.

In the last three months alone, Gerald’s mum went viral for a microphone mishap, Adam’s mum shot to Twitter fame for failing to understand WhatsApp, Lois’ mum got tricked by her daughter, Harry’s mum was hit in the head with a football, Hanna’s mum misunderstood a hairstyle, and Jake’s mum failed to notice her son had swapped a photo in her home for a portrait of Kim Jong-un.

But how do the mothers behind these viral tweets feel?

“I'm pretty much a mum that everybody wants to talk to these days,” says Terri, with another warm laugh. The mum of three says going viral “is not that big of a deal” to her, but she is happy that her son can enjoy being a “local superstar”. But is she embarrassed at being the punchline of Jeff’s joke?

“Believe me, I have thick skin,” she says. “I kinda look at what it is, and it’s actually him and his fame. I’m just the mum behind it, the butt of the joke, but I don't mind.”

Not all mums feel the same. A handful of similar viral tweets have since been deleted, indicating the mothers featured in them weren’t best pleased. A few people I reach out to haven’t actually told their mums that they’re the subject of viral tweets, and other mums simply don’t want any more attention.

“I think I’ve put my mum through enough with that tweet already,” says Jacko, when I ask if his mum would be willing to be interviewed. In 2014, Jacko tweeted out a picture of his family writing the word “cock” in the air with sparklers. “This is still my favourite ever family photo,” he captioned the tweet, “My mum did the ‘O’. We told her we were going to write ‘Love’.”

“No one ever expects to call home and say ‘Mum, have you heard of something called LADbible? No, you shouldn’t have, it’s just that a quarter of a million of its fans have just liked a photo of you writing the word ‘cock’ with a sparkler’,” Jacko explains.

Although Jacko feels his mum’s been through enough with the tweet, he does say she was “ace” about her new found fame. “She’s probably cooler about it all than I am”. Apart from the odd deletion, then, it seems most mums are happy to become viral Twitter stars.

Yet why are mums so mocked and maligned in this way? Although dads are often the subject of viral tweets, this is usually because of jokes the dads themselves make (here’s the most notable example from this week). Mums, on the other hand, tend to be mocked for doing something “wrong” (though there are obviously a few examples of them going viral for their clever and cunning). On the whole: dads make jokes, mums are the butt of them.

“We all think our mums are so clueless, you know. They don’t know what’s going on. And the fun thing is, one day we come to realise that they knew way more of what was going on than we thought,” says Patricia Wood, a 56-year-old mum from Texas. “People always kind of make fun of their mums, but love them.”

Last year, Patricia went viral when her daughter Christina tweeted out screenshots of her mum’s Facebook posts. In them, Patricia had forgotten the names of Christina’s friends and had candidly written Facebook captions like: “My gorgeous daughter and her date for formal, sorry I forgot his name”. Christina captioned her tweet “I really can't with my mom” and went on to get more than 1,000 likes.

“I felt, like, wow, it was like we’re famous, you know. I thought it was really cool,” says Patricia, of going viral. Her experiences have been largely positive, and as a part-time Uber driver she enjoys telling her customers about the tweet. “But I did have one bad experience,” she explains. A drunken passenger in her car saw the tweet and called Patricia an “asshole”.

Another aspect of viral fame also worried Patricia. She and her daughter were invited on a reality show, TD Jakes, with the production company offering to pay for flights and hotels for the pair. “I have too many skeletons in my closet and I didn't want them to come dancing out,” says Patricia, of her decision not to go. “By the time I got off it, it would be the Jerry Springer show, you know. I’m kind of a strange bird.”

On the whole, then, mothers are often amused by going viral via their offspring – and perhaps this is the real beauty of tweeting about our mums. Since the moment they earn the title, mums can’t afford to be fragile. There is a joy and relatability in “my mum” tweets – because really, the mum in question could be anyone’s. Still, from now on, mums might be more careful about what they tell their sons and daughters.

“When I send Jeff a text now I make sure I’m like: ‘Is my spelling correct? Is what I’m saying grammatically correct?’,” says Terri, “Because who knows where the words are gonna end up?”

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

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