Mechanical evidence of the orbital angular momentum to energy ratio of vortex beams

April 24, 2012 10:00 AM

"We measure, in a single experiment, both the radiation pressure and the torque due to a wide variety of propagating acoustic vortex beams. The results validate, for the first time directly, the theoretically predicted ratio of the orbital angular momentum to linear momentum in a propagating beam. We experimentally determine this ratio using simultaneous measurements of both the levitation force and the torque on an acoustic absorber exerted by a broad range of helical ultrasonic beams produced by a 1000-element matrix transducer array." In other words, science has created the sonic screwdriver, and it could mean new advances in non-invasive surgery.

The official release from the University of Dundee, plus a couple of videos. Still doesn't work on wood.

posted by jbickers (12 comments total)

I must confess that I do not understand about 90 percent of the nouns in this post, but 'sonic screwdriver' sounds to me like magic and I heartily approve.
posted by tivalasvegas at 10:08 AM on April 24, 2012 [5 favorites]

Why does the BBC put "invented" in scare quotes?
posted by eugenen at 10:22 AM on April 24, 2012

eugenen: “Why does the BBC put ‘invented’ in scare quotes?”

Because it's weird to say that someone invented something that was created by a popular television show?
posted by koeselitz at 10:29 AM on April 24, 2012

Also, they went an interesting route with this in making it bigger on the outside than it is on the inside.
posted by koeselitz at 10:30 AM on April 24, 2012 [2 favorites]

Wow, cool. Vortex beams have been a big subject in optics for a while now but I've never heard of acoustic ones. I wish they had a preprint - would be interesting to know things like the beam divergence. Also, the disc they levitate is 90 g but I wonder how much heavier that is than the displaced water (ie what is the actual lifting force generated).

The BBC uses inverted commas like crazy in their headlines. They reached peak inverted commas about 6 months ago and have actually backed off a lot since - reading the headlines display on their mobile site used to drive me nuts. In this case, it's because they haven't literally invented a sonic screwdriver. For example, I think this one actually would work on wood if you drove it hard enough.
posted by Pre-Taped Call In Show at 10:34 AM on April 24, 2012 [1 favorite]

I love sci-fi, and I love science, but when the too meet in a press release, it fills me with blinding rage. At least its been a while since we got one of those "one step closer to Harry Potter's invisibility cloak" headlines
posted by Chekhovian at 10:35 AM on April 24, 2012 [1 favorite]

peak inverted commas

And with this comment, we have reached peak 'peak-labeling'. Well played, Pre-Taped Call In Show.

Questions for people who Know About Science: what are the practical implications of this? Is being able to turn things with sound a transformative ability or does it just make it easier to do things that could be done with previous techniques (granted I didn't really know that we were moving things in straight lines with sound, so I may be not-even-wrong here)? Is this scalable to larger efforts or would that be theoretically or practically impossible?

Honestly, I just want to know if this will lead to man-made tornadoes so that I can prepare accordingly.
posted by tivalasvegas at 10:56 AM on April 24, 2012

Can it reverse the polarity of a neutron flow?
posted by Mister Moofoo at 11:42 AM on April 24, 2012 [1 favorite]

What, you've never had a long night? Never had a lot of cabinets to put up?
posted by cmyk at 11:45 AM on April 24, 2012

what's the progress report on the quantum spanner?
posted by mwhybark at 12:19 PM on April 24, 2012 [1 favorite]

Can someone read this post to me in Leonard Nimoy's voice? Thanks.
posted by gimonca at 1:16 PM on April 24, 2012 [1 favorite]

Honestly, I just want to know if this will lead to man-made tornadoes so that I can prepare accordingly.

More specifically, you fear a future of man-controlled tornadoes. Man-made tornadoes... it's starting to look like we accidentally did that already, while we weren't paying attention. (Oops. Sorry.)

But it raises the question: What does a sonic tornado sound like?
posted by -harlequin- at 10:44 PM on April 27, 2012