Axis of upheaval: it's a twist that not even Einstein expected. Stuart Clark goes in search of gravity's secret.(Cover story)
Article from: New Scientist | November 11, 2006 | Clark, Stuart
GRAVITY has a secret side. As well as the brute force that holds us to the ground, large masses should also exert a subtle swirling influence when they rotate, a force called gravitomagnetism. It's so faint that a NASA spacecraft called Gravity Probe B has been orbiting the Earth for over two years to accrue enough evidence to have a chance of confirming this force.
Yet in a lab in Austria, Martin Tajmar and his team have already succeeded in detecting a faint signal that seems to be due to this elusive component of gravity. A reason for celebration? Not quite. Puzzlingly, the force they seem to have generated is vastly more powerful than anyone else expected.
Despite its name, gravitomagnetism has nothing to do with magnetic fields as we think of them. According to Einstein's general theory of relativity, a rotating mass such as a planet should twist the fabric of space-time, and any object nearby should be dragged around by the vortex. It is really just another case of matter telling space-time how to curve and space-time telling matter how to move. lust [sic] as a stationary mass creates a "dip" in space-time that we perceive as gravity, a rotating mass creates a twist in space-time. [Blue emphasis mine. dem]
This gravitomagnetism is a feeble phenomenon: an object orbiting close to the Earth should be shifted just a few nanometres per year. In contrast, the gravitomagnetic force Tajmar's team have seen is trillions of times stronger, which is why they are treating the results so cautiously. What's more, their force is only generated by a spinning superconductor, not any other kind of matter.† "We cannot find a mechanism to explain this in either general relativity or quantum mechanics," says Clovis de Matos, who works at the European Space Agency in Paris and helped establish the theory behind the experiment.
Their startling measurement might point towards a new quantum theory of gravity. It might even herald a futuristic technology that could be used to pull, push or levitate any object, regardless of its composition, electrical charge or shape. With so much at stake, it's no wonder Tajmar and his collaborators are treading carefully. "We tried everything we could think of to make this reading go away," says Tajmar. And yet after three years and more than 250 experimental runs at the Austrian Research Centers facility in…
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