23 March 2006

Laboratory Scale Frame Dragging Experiment.

General relativity predicts an effect known as frame dragging, also known as gravitomagnetism. Just as electrical charges in motion can create magnetic fields, moving masses, in theory, under general relativity, can create gravitational fields analogous to electromagnetic fields where the primary gravitational effect is similar to an electrical field.

But, gravitomagnetic fields are generally predicted to be so faint that they can only be detected with supersophisticated equipment a carefully chosen locations in space. But, now some experimenters claims to have discovered the same kinds of frame dragging phenomena in a relatively ordinary physics laboratory, using relatively common place superconductors.

This would allow precise general relativity experiments to be conducted for tens or hundreds of thousands of dollars, instead of tens or hundreds of millions of dollars. Previously, while a small number of existing general relativity tests, like Gravity Probe B, can be conducted on a truly experimental basis at an immense cost that makes them hard to reproduce experimentally, and special relativity is comparatively easy to test in a laboratory, most general relativity research has been conducted with telescopes on an observational basis, which makes precision difficult to secure because so many of the masses and distances involved themselves have considerable experimental uncertainty associated with them. The results described in the pre-print linked above will probably be the subject of replication attempts that will prove or disprove the experimental results claimed within a few years, or less.

How could this effect be observed at this scale? The theory that motivated this experiment is that gravity is carried by a long hypothesized particle called a graviton, and that in this highly controlled environment, that graviton gains mass, thus greatly amplifying the frame dragging effect.

While general relativity has long been observed and confirmed at large scales, small scale gravity tests have proven difficult to conduct and the mechanism by which gravity operates at a distance has been largely confined to theory without any empirical basis. The main camps in the debate have been those who have preferred to model gravity with a carrier particle, much like other forces, and those who have advanced theories of quantum gravity which are fundamentally geometric in nature, proposing that time-space itself in quantitized. This experiment is one of the strongest indicators to date that gravity does have a quantum carrier particle, and it suggests avenues for further investigation of that hypothesis.

Some in the blogosphere have described this experiment as a radical disproof of Einstein's Theory of General Relativity, because the effect that is observed is much larger than one would conventionally expect to see. But, their mechanism of graviton mass gain, a theoretically well developed concept, bridges the gap between mainstream quantum theory and mainstream general relativity in a manner that really doesn't disprove well established theories in either realm.

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