ACCORDING to the Old Testament, the Lord empowered Moses to part the waters of the Red Sea and rescue the Israelites from the ruling pharaoh’s army and certain annihilation. It was quite a stunt. But the Lord’s trick has now been stolen by a band of physicists in Europe, Japan and the US, who have unleashed it in the laboratory.
Shoogo Ueno and Masakazu Iwasaka of the University of Tokyo first had the audacity to mimic Moses back in 1994, albeit on a scale somewhat less than biblical. Their Red Sea was a simple horizontal tube filled halfway with water and enveloped by a coil of superconducting wire. There was no raising of hands, or slaughtering of lambs, or even praying. They just plugged in the coil. Electrical currents swirled, a magnetic field filled the tube, and the water fled from the centre into the ends, leaving a bone-dry gap in the middle.
In the past few years, researchers have discovered that the magnetic coil is a modern day, all-purpose Moses. Not only can it part water, but it will nullify the inexorable pull of gravity, and make strawberries, grasshoppers, fish and frogs hover like ghosts in midair. The miracles of the prophets can finally be duplicated, and not by mere trickery-the science of sorcery has come of age.
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God-fearing men and women may find some solace in the fact that magnets strong enough to defy gravity are awfully hard to come by. The field inside Ueno and Iwasaka’s magnificent coil was about 500 000 times stronger than that created by the Earth, and only a handful of labs on the planet can match it. But it may seem truly miraculous that magnets, no matter how strong, can affect water. Water isn’t magnetic. So what gives?
Mild distaste
At first, Ueno and Iwasaka were just as shocked by the effect as anyone else. “The mechanism wasn’t known,” says Koichi Kitazawa, a colleague of theirs at the University of Tokyo. But Kitazawa became intrigued. He named the miracle “The Moses Effect,” and set out to explain it. To find clues, he had to look no further than the piles of old nuts and bolts, nails and screws that lay about his lab.
Like water, these things aren’t naturally magnetic. But they will turn magnetic with a bit of persuasion-bring a magnet near a nail, and the nail itself becomes magnetised. Once persuaded in this way, materials can act in two entirely different ways. “Paramagnetic” materials, such as metals, enjoy being magnetised and, in fact, to become magnetised as fully as possible, they seek to move to places where the magnetic field is high. As a result, a nail will nuzzle right up to a magnet.
But water has other ideas. “Water is weakly diamagnetic,” says Kitazawa, which means that although it is mostly indifferent, it has a mild distaste for being magnetised. So a powerful magnet repels water, and drives it from places where the magnetic field is high to others where it is low. Using this idea, Kitazawa worked out a precise theory that explains The Moses Effect. In Ueno and Iwasaka’s coil, the field is strongest in the middle and tapers off towards either end. So the water naturally just squirts out to the sides.
How the Lord originally did the trick is anyone’s guess. But pushing water around is easy-if you have a big enough magnet. And if you do, then nearly anything is possible. In their lab at the University of Nijmegen in the Netherlands, physicists Andre Geim, Jan Maan and their colleagues use a powerful magnet to study the electronic and optical properties of materials in high magnetic fields. Last year, in collaboration with researchers from the University of Nottingham, they coaxed a shopping list of objects to float in midair in the lab, including everything from hazelnuts and tulips to the spotted eggs of grouse.
And that’s nothing. “It’s possible to levitate every creature on Earth,” says Geim. An action photo of one aviator, taken mid-flight, shows a poised and confident frog, with its legs folded and arms spread strategically to maintain a perfect diver’s balance (In Brief, 12 April, p 13).
The flying frog is the last in a series of gravity-defying stunts that began even before waters had been parted in Japan. Back in 1991, researchers at the French national research (CNRS) laboratory in Grenoble used big magnets to suspend chunks of wood and plastic, as well as globules of water in midair. All these things-and frogs, too-are diamagnetic. They abhor intense magnetic fields, and naturally seek regions where the field is weaker. Generate a field that is strongest below an object and weaker above, and an upward magnetic force can cancel the force of gravity.
Grizzly bear cubs
This is easy to do with a magnetic coil simply turned on end. The field is strongest at the middle, weaker at the upper end, and almost any tiny object will hover in between. Frog embryos, for instance, hover just as well as fully grown frogs, as physicist James Valles and colleagues at Brown University in Providence, Rhode Island, have discovered. Beetroot, grizzly bear cubs, chunks of oxtail, even the dry bones of your favourite saint-the magnet affects one and all.
Strong magnets are the world’s first real antigravity devices. In future, NASA astronauts might use magnets on Earth to simulate the microgravity of space. At present, they use swimming pools-which are poor simulators of microgravity. As Valles points out, “floating an object doesn’t mimic weightlessness, because the forces that hold it up act only on the surface”. When floating in a pool, for example, the water pushes up against your skin, but the various bits of your guts still press against one another.
But Geim cautions that magnetic levitation isn’t perfect, for in a living creature, bones, kidney, heart, and the rest consist of different materials. The magnetic force on each is slightly different. This would spell trouble in an extremely strong field-say near the Sun-where the force mismatch would shred a human body into ribbons. Fortunately, in a field strong enough to achieve levitation on Earth, the force mismatch would be tiny, creating stresses about 10 times weaker than the body experiences under normal gravity.
Bill Hones, an inventor based in Seattle, Washington, is talking about levitating a human in this way. Hones is the creator of a toy that he calls the Levitron. It’s a top that hovers, when spinning, over a magnetic base. But Hones has bigger plans. To celebrate the millennium he wants to use 2 per cent of Seattle’s power supply to magnetically levitate a person a few tens of metres above the ground. “It would be fascinating to behold,” he says. Levitating a human is the easy part, it may take more than a miracle for Seattle’s midwinter power consumers to give him the chance.