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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All 27 things wrong with today’s Daily Mail front cover

Where do I even start?

Hello. Have you seen today’s Daily Mail cover? It is wrong. Very wrong. So wrong that if you have seen today’s Daily Mail cover, you no doubt immediately turned to the person nearest to you to ask: “Have you seen today’s Daily Mail cover? It is wrong.”

But just how wrong is the wrong Mail cover? Let me count the ways.

  1. Why does it say “web” and not “the web”?
  2. Perhaps they were looking on a spider’s web and to be honest that makes more sense because
  3. How does it take TWO MINUTES to use a search engine to find out that cars can kill people?
  4. Are the Mail team like your Year 8 Geography teacher, stuck in an infinite loop of typing G o o g l e . c o m into the Google search bar, the search bar that they could’ve just used to search for the thing they want?
  5. And then when they finally typed G o o g l e . c o m, did they laboriously fill in their search term and drag the cursor to click “Search” instead of just pressing Enter?
  6. The Daily Mail just won Newspaper of the Year at the Press Awards
  7. Are the Daily Mail – Newspaper of the Year – saying that Google should be banned?
  8. If so, do they think we should ban libraries, primary education, and the written word?
  9. Sadly, we know the answer to this
  10. Google – the greatest source of information in the history of human civilisation – is not a friend to terrorists; it is a friend to teachers, doctors, students, journalists, and teenage girls who aren’t quite sure how to put a tampon in for the first time
  11. Upon first look, this cover seemed so obviously, very clearly fake
  12. Yet it’s not fake
  13. It’s real
  14. More than Google, the Mail are aiding terrorists by pointing out how to find “manuals” online
  15. While subsets of Google (most notably AdSense) can be legitimately criticised for profiting from terrorism, the Mail is specifically going at Google dot com
  16. Again, do they want to ban Google dot com?
  17. Do they want to ban cars?
  18. Do they want to ban search results about cars?
  19. Because if so, where will that one guy from primary school get his latest profile picture from?
  20. Are they suggesting we use Bing?
  21. Why are they, once again, focusing on the perpetrator instead of the victims?
  22. The Mail is 65p
  23. It is hard to believe that there is a single person alive, Mail reader or not, that can agree with this headline
  24. Three people wrote this article
  25. Three people took two minutes to find out cars can drive into people
  26. Trees had to die for this to be printed
  27. It is the front cover of the Mail

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