Leave your anti-gravity books at the door
Levitation: no longer the stuff of magic shows
“What we want to do, for a number of reasons, is to make things float in mid-air,” explains Peter King, a man whose job is to defy gravity.
It sounds amazing, and he’s getting better at it. This month the latest refinements to his technique were released, along with video footage of chunks of platinum, lead and pound coins floating freely in a glass jar. As a result he’s been in demand – national newspapers were interested, television networks even travelled across the Atlantic.
But King thinks they missed the point: “You say you can float something using a magnetic field, and ten minutes later it’s ‘scientists discover an antigravity machine’. This is not quite what we’ve done – we’re not having free trips to Mars tomorrow in our antigravity machine.”
So just what has King’s research group at the University of Nottingham done? When he tells the story his way, it emerges that an elegant piece of research has largely been ignored in favour of the allure of the word ‘levitation’ and myths of antigravity skateboards.
It turns out that levitation is actually nothing new – water, strawberries and frogs have all been levitated before using a phenomenon called diamagnetism, as King explained: “Diamagnetic materials absolutely hate magnetic fields and experience a force driving them out of them.” This force can balance out gravity and make things levitate, but only up to a density like that of water. This limits the usefulness of levitation, but in 2003 King’s group improved on this by harnessing an opposite effect.
It is another electromagnetic phenomenon – paramagnetism – that is the opposite of diamagnetism. Paramagnetic materials are strongly attracted to a magnetic field, and liquid oxygen is one example. King found that it could strongly enhance levitation – as it strives to get close to the electromagnet, the liquid gas displaces the floating material even higher. Much denser materials like diamond, platinum and lead could now be levitated.
This was a major step forward, but with a potentially dangerous catch. Liquid oxygen, rocket fuel, is massively explosive. It made levitation much more useful and dramatic, but its volatility rendered applications outside the lab unimaginable. The real story of King’s recent results is that he has solved this potentially explosive problem.
The secret is using a mixture of liquid gases. Oxygen is still used, but diluted to one part in eight by calmer nitrogen: “You can actually dilute oxygen a lot and still float things pretty well. It’s clean too – nitrogen and oxygen in those proportions is just air. If we lose that back into the atmosphere, nobody shouts at us.”
Safe, clean levitation of dense objects allows more useful applications than making frogs ‘air sick’. First in line is the mining industry – levitating metals or gems offers a more efficient way of separating them from soil. This is the real tale of King’s latest research. Levitation is in the end, perhaps literally, too down to earth for the media circus, but hearing the details of this story from the horse’s mouth beats sci-fi speculation hands down.
