# 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
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# Are cats solid or liquid? 13 of the best winners of the Ig Nobel prize

This satirical awards ceremony has celebrated unusual contributions to science for 27 years.

Every year, the Ig Nobel Prize Committee hands out ten awards. A parody of the Nobel Prize, it recognises some of the most whimsical contributions to science.

Categories include psychology, fluid dynamics and chemical engineering, much like the real Nobel Prizes, but change year to year. Its name is a pun on the word ignoble.

Studies that won prizes this year include a paper which discovered which part of the brain creates repulsion to cheese, a report on the effects of human blood in the diet of hairy-legged vampire bats, and research explaining why old men have big ears (gravity). The winners are just the latest in 27 years of the award. Here are 13 of the most head-scratching and unique winners:

#### 1. Original conspiracy theories

Erich Von Daniken won the Literature Prize in 1991, the first year of the Ig Nobel awards, for his book Chariots of the Godswhich suggested human life takes its origins from ancient aliens that came to earth. Originally published in 1968, the book imagines that many ancient civilisations demonstrated higher scientific abilities than was possible given the limitations of their time, so aliens must have come to Earth and transmitted the knowledge to make human progress possible.

#### 2. The Antichrist from the East

Robert Faid, a mathematician, invested a huge amount of time in calculating the exact odds of whether Mikhail Gorbachev, the final leader of the Soviet Union, is the Antichrist. (The exact odds are 710,609,175,188,282,000 to 1, if you’re curious).

#### 3. Refined pigeons

Shigeru Watanabe, Junko Sakamoto and Masumi Wakita successfully trained several pigeons to discriminate between Picasso’s paintings and Monet’s paintings, a skill that some humans might still be struggling with.

#### 4. Lovesick

Four scientists at the University of Pisa discovered that the biochemical basis of romantic love might not be all that different from the biochemical basis of neuroticism and Obsessive Compulsive Disorder, as they observed the multiple ways that platelet serotonin was transported around various sections of the brain.

#### 5. Hell is closer than we think

Dr. Jack Van Impe and Rexella Van Impe carried out research which demonstrated that one of the universe’s great mysteries, black holes, fulfil the theological and technical requirements to be the location of hell itself.

#### 6. Feathery feelings

Stefano Ghirlanda, Liselotte Jansson, and Magnus Enquist of Stockholm University demonstrated that our flightless friends may be no different to us – in that chickens prefer beautiful humans. Chickens were more likely to react to pictures of faces that were deemed more conventionally attractive.

#### 7. Creative (non) fiction

This went to a whole group of people in Nigeria, the internet entrepreneurs who used e-mail to introduce many innocent fraud victims around the world to “a cast of rich characters – General Sani Abacha, Barriste Jon A Mbeki Esq”, who find themselves in need of a loan and rely on the generosity of strangers to access their own immense fortunes.

#### 8. Say Cheese

Nic Svenson and Piers Barnes of the Australian Commenwealth Scientific and Research Organisation did all the legwork and found the exact number of photographs that you have to take in order to ensure that nobody in a group photo will have their eyes closed.

#### 9. A girl's best friends

Three scientists at the Universidad Nacional Autónoma de México were able to create a girl’s best friend, diamonds, from her other best friend, tequila. They did this by heating tequila at very high temperatures to turn it into a gas. They then heated the gas further to break it into solid crystals that had the same composition as pure diamonds.

#### 10. Swearing is good for you

Richard Stephens, John Atkins and Andrew Kingston of Keele University finally proved that there’s a scientific basis for the belief that swearing relieves pain. It may have something to do with how swearing can nullify the typical fight-or-flight response to pain, among other reasons.

#### 11. Beer goggles

Five scientists, Laurent Begue, Brad Bushman, Oulman Zerhouni, Baptiste Subra and Medhi Ourabah, confirmed that “beauty is in the eye of the beer holder” ie that if you’re drunk, you’re more likely to think you’re attractive.

#### 12. More than a pet rock

Mark Avis, Sarah Forbes and Shelagh Fergon were able to use a sales and marketing perspective to ascertain the potential personalities of various kinds of rocks, by interviewing focus groups who said what they believed the rocks could be like. Some rocks (particularly the more fetching ones) were described as "classy, feminine", while others were seen more as "a hippy, someone who believes in star signs and whatnot".

#### 13. The internet's favorite animal

Marc-Antoine Fardin sought to answer the age old question: cats – liquid or solid? Apparently, they're both. (Fardin admits there’s much more research to be done).

A full list of every year's winners can be found here