# 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.

Flickr: M.o.B 68 / New Statesman
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# “I begged him to come home”: Breaking the taboo around texting the dead

Many people text dead loved ones to cope with their grief – but trouble arises when they get an unexpected reply.

A month after Haley Silvestri’s dad died from a heart attack, she texted him begging him to come home. In the middle of the night Silvestri’s 14-year-old sister had found their father, with his lips and mouth blue, lying on the kitchen floor. “There was nothing there anymore, just a dead body,” Silvestri says. “My father had his first heart attack months before and seemed to be doing OK. Then, this happened.”

In the very first episode of CSI Miami’s seventh season, the protagonist – Horatio Caine – fakes his death. For the first 15 minutes of the episode, the viewer believes the character is truly dead, as the camera lingers on Horatio’s body face down on the tarmac.

Silvestri and her father used to enjoy watching the show together. After he had passed and she realised she would never see her “best friend” again, she picked up her phone. “I texted my dad begging him to come home,” she says. “I begged my dad to please be ‘pulling a Horatio’.”

"My heart was broken and I was bawling as I texted her over and over"

In texting her father after he had died, Silvestri is by no means unusual. No official figures exist for the number of people who use technology to message their deceased loved ones, but Sara Lindsay, a professional counsellor, clinical supervisor, and trainer, says it is “more common than we think”.

“I see it as a modern and contemporary part of the grieving process,” she says. “I think in a way it's very similar to visiting a graveside, in that the bereaved are reaching out, particularly in the early days, because it takes a long time for people to process the reality that this person has now gone.”

Karlie Jensen, 18, texted her friend immediately after she found out she had died in a car accident. “I texted her as soon as I woke up to the news from my mom that she had passed. My heart was broken and I was bawling as I texted her over and over waiting for a text saying it wasn't her, that my mom didn't know all the facts, and maybe she was just hurt.” Jensen also called her friend and begged her to respond. “I did it because I couldn't let go and couldn't accept she was gone from my life forever,” she says. Karlie continued to text her friend while also calling her voicemail in order to hear the sound of her speaking again.

Karlie (right) and her friend

After her first text to her deceased father, Silversti also began texting him once a week. She fell into depression, and on her worst days messaged the number. “I think it helped initially because it felt like I was personally writing a note to him, that I knew he only was gonna see,” she says. “I did it because it was my attempt at pretending he was still here and could text me back.”

Lindsay, who has over a decade’s experience of bereavement counselling, emphasises that this behaviour is in no way unhealthy. “I think on the whole it's a very healthy part of grieving, particularly in the first year where the bereaved faces agonising days without their loved ones,” she says. “There is just so much loss and change in their life that’s out of their control, I see this aspect of texting as a small way of being able to reach out and alleviate that pain. That person is suddenly now not there but how they feel about that person hasn't changed.”

"I was going through my phone and I saw his number – I wanted to delete it, but I hesitated I thought maybe I could send a text"

Despite being normal, however, using technology to talk to the dead is a behaviour we rarely – if ever – hear anything about. If the words “texting the dead” make it into the media, they are usually followed by a far more sensationalist “and then they text back!!!!”. Yet although messaging the deceased is popularly seen as the stuff of horror movies and trashy headlines, in reality it is simply a new, modern way to grieve.

Via Mirror.co.uk

“The first time I texted him I was on my bus on the way to school,” says now-20-year-old Dylan Campbell about his cousin Josh, who passed away from leukaemia. “I didn't have many friends so I had no one to talk to. I was going through my phone and I saw his number – I wanted to delete it, but I hesitated I thought maybe I could send a text and someone would reply or I would get something out of it.”

Campbell continued to send his cousin texts for a few weeks, “kind of like a diary”. He says he did so because he regretted not seeing Josh more up until his death, and “had a lot of things to say” that he’d never had the chance to. Linsday says texting in this way is a very healthy way of completing unfinished business. “There might have been something they've never said to their loved one that they want to be able to say and texting is a very normal place to do that.”

"Begging for a dead person to reply to you hurts since you won't ever get what you want in return"

Nonetheless, Lindsay notes that texting the dead can become unhealthy if grief becomes “stuck”, and the texting replaces normal communication or becomes a long term compulsion. Unlike Silvestri and Campbell, Jensen continued to text her friend in the hopes she would text back. She admits now that she was in denial about her death. “Begging for a dead person to reply to you hurts since you won't ever get what you want in return” she says. “I don't know if it helped trying to contact her or hurt worse because I knew I'd never get a reply. I wanted a reply.”

Quite frequently, however, this reply does come. After a few months – but sometimes in as little as 30 days – phone companies will reallocate a deceased person’s phone number. If someone is texting this number to “talk” to their dead loved one, this can be difficult for everyone involved.

“This story doesn't have a happy ending,” says Campbell. “After a few months someone from that number called me and yelled at me to stop bothering them – it was really heart breaking.” When Silvestri texted her father to wish him a happy birthday (“Saying I hoped he was having a great party up in heaven”) someone replied telling her to never text the number again. “I was pissed off,” she says. “Just block my number if it was that serious. This was a form of therapy I needed and it got taken away because someone couldn’t understand my hurt.”

Indeed, behind the sensationalist tabloid headlines of "texting back" is a more mundane - and cruel - reality of pranksters pretending to be the dead relatives come back to life.

"Visiting a grave is a clear recognition that the person visited does not exist in the normal day-to-day state of life, whereas texting allows for a suspension of that reality"

Silvestri, Jensen, and Campbell have never spoken to anyone else about the fact they texted their dead loved ones. Lindsay says that a fear of seeming “mad” combined with cultural phenomena – like the British stiff upper lip – might make people reluctant to speak about it. There is also a stigma around the way much of our modern technology is used in daily life, let alone in death.

This stigma often arises because of the newness of technology, but Christopher Moreman, a philosophy professor and expert on death and dying, emphasises that texting the dead is simply a modern iteration of many historical grieving practices – such as writing letters to the dead or talking to them at their graves. “I don't think the process of grieving is much changed, even if new modes of grieving come about due to new technologies,” he says. In fact, if anything, the differences between old and new ways of grieving can be positive.

“One important difference is in the sense of proximity,” explains Moreman. “I can text a loved one from anywhere in the world, but I can only visit their grave in one specific location. In another way, texting has the same structure whether I am texting someone who is alive or dead, so a sense of proximity also exists in the experience itself.

“Visiting a grave is a clear recognition that the person visited does not exist in the normal day-to-day state of life, whereas texting allows for a suspension of that reality. Some people may complain that new technologies allow us to ignore the reality of death, but there isn't any evidence that one way of grieving is more or less healthy than another.”

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

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