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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Relax – there’s new evidence that mindfulness actually works

The relaxation therapy could prevent relapses in sufferers of depression, according to a new study.

If there’s one thing that can be said of buzzwords, it’s that they almost always fall by the wayside in the end. Yet in the field of mental health, one buzzword has survived the best efforts of critics and naysayers – “mindfulness”.

First coined by Dr Jon Kabat-Zinn from the University of Massachusetts Medical School, the term mindfulness was initially characterised as a state of mind that would enable someone to pay “attention on purpose” to the present moment. Modern secular society seems to have embraced it as a form of meditation. Everything from exercise to breathing now has an associated mindfulness manual attached.

However, not everyone is convinced. For example, the recent phenomenon of adult colouring books – devised to promote mindfulness and serve as a form of therapeutic escapism – has been criticised by therapists as over-hyped and not necessarily helpful.

Meanwhile, sceptics have pointed out an alleged bias in the publishing of positive findings from trials using mindfulness as a form of mental health therapy. Researchers at McGill University in Canada “found that scientists reported positive findings 60 per cent more often than is statistically likely” after analysing 124 different published trials involving mindfulness as a form of mental health therapy. In some cases, the practice has even had a reverse effect, inducing anxiety, pain or panic.

However, a new study published in the journal JAMA Psychiatry seems to demonstrate that mindfulness-based cognitive therapy (MBCT) can be a potent treatment in preventing and managing relapse into major depression. Led by the University of Oxford, the study’s researchers conducted the largest meta-analysis (an analysis of various different studies) to date on the therapy’s impact on recurrent depression.

The particular form of mindfulness-based cognitive therapy that was used aimed to equip patients with the skills required to successfully recognise and repel the thoughts and feelings they most commonly associated with the state of depression, in order to prevent any future relapse.

According to the study, “the MBCT course consists of guided mindfulness practices, group discussion and other cognitive behavioural exercises. Participants receiving MBCT typically attended eight 2-2.5 hour group sessions alongside daily home practice.”

Using anonymous patient data from nine randomised trials involving 1,258 participants, researchers found that 38 per cent of those who received mindfulness-based therapy experienced a depressive relapse, in comparison to 49 per cent of patients who didn’t receive treatment. The patient data covered age, sex and level of education – key inclusions, as the meta-analysis was able to show no significant influence by these factors on the therapy’s performance.

The most prominent form of remedy currently available for mental health patients is anti-depressant medication. Four of the nine randomised trials comparatively assessed the impact of therapy alongside medication, to deduce if a combination of therapy with varying doses of medication was more beneficial than medication alone. The patients from the study who received mindfulness therapy along with continued, reduced or discontinued medication were less likely to fall back into depression than patients on maintenance anti-depressants alone. This helps legitimise mindfulness as an option in combating depression’s debilitating effects and reinforces its efficacy, whether it is taken up with or without anti-depressants.

Willem Kuyken, Professor of Clinical Psychology at the Oxford Mindfulness Centre and lead author of the study, called the results “very heartening”. “While MBCT is not a panacea, it does clearly offer those with a substantial history of depression a new approach to learning skills to stay well in the long-term.

“It offers people a safe and empowering treatment choice alongside other mainstay approaches such as cognitive-behavioural therapy and maintenance antidepressants. We need to do more research, however, to get recovery rates closer to 100 per cent and to help prevent the first onset of depression, earlier in life. These are programmes of work we are pursuing at the University of Oxford and with our collaborators around the world."

Though the findings will certainly reinvigorate confidence in mindfulness, Richard Byng from the University of Plymouth and one of the co-authors said, “clinicians need to be cautiously optimistic when tapering off antidepressant medication, and treat each patient as an individual who may or may not benefit from both MBCT and other effective treatments."