Lots of giddy excitement this week about a tractor beam that has been developed by a joint team from Bristol and Sussex universities. Lots of ‘Darth Vader had one, the Starship Enterprise had one’ stuff.
Let’s not get too excited just yet. The object they managed to suspend in air and manoeuvre was a 4mm polystyrene ball. With that sort of power available it’s not going to present the Millennium Falcon with too much of a problem. And since it works as a repellant, it’s not a tractor beam, it’s a pulsar beam, because it pushes not pulls.
The boffins used an array of 64 miniature loudspeakers to create high frequency, high intensity sound waves. They then fiddled with the settings a bit to hold the ball in suspension, move it, or rotate it. Clever stuff nonetheless. But the team make some pretty far-fetched claims.
‘Unprecedented acoustic structures shaped as tweezers, twisters (sic), or bottles emerged as the optimum mechanisms for tractor beams or containerless transport,’ they babbled, suggesting that the technique could be applied to levitating living things.
I somehow doubt that. High intensity sound packs a lot of energy, and can be pretty destructive. But let’s assume it may be true.
Then lots of breathy enthusiasm that, ‘Single beam levitation could manipulate particles inside our body for applications in targeted drug delivery or acoustically controlled micromachines that do not interfere with magnetic resonance imaging.’ I haven’t been able to find anything about why this is an issue, or whether it’s just PR puff.
An intriguing idea. But then one of the PhD students working on the project goes native. Asier Marzo, for it is he, claims that more powerful beams could manipulate heavier objects at greater distances. Yes, I can see that. But then he drops the ball, claiming that such a device might allow astronauts to manipulate objects floating in space without leaving the safety of the space capsule.
A reasonably intelligent and knowledgeable child can spot the flaw here. Space is as close to a hard vacuum as you get. There’s no air, no other fluid in anything at a higher concentration than a molecule per cubic metre. No air = no sound. Despite all the whizzbangery in sci fi films, space is as silent as the grave. So the acoustic tractor beam isn’t going to work, is it?
You’d expect a PhD researcher in acoustics to know that, wouldn’t you? I’d also expect the science editors in the media to clock this as well, and not actually print this twaddle.