Thursday, May 5, 2011

Frame dragging confirmed

Today's science news is that Einstein was right:
Four superconducting ping-pong balls floating in space have just confirmed two key predictions of Einstein’s general relativity, physicists announced in a press conference May 4.

“We have completed this landmark experiment testing Einstein’s universe, and Einstein survives,” said physicist Francis Everitt of Stanford University, the principal investigator on NASA’s Gravity Probe B mission.

The probe, which launched in 2004, was designed to test the effect Earth’s gravity has on the space-time around it. According to Einstein, the Earth warps its local space-time like a bowling ball sitting on a trampoline, a phenomenon called the geodetic effect. This effect means that a circle of fabric with the Earth’s circumference, about 24,900 miles, would be pulled into a shallow cone with a circumference 1.1 inches shorter.

The Earth also swirls the nearby space-time around with it as it rotates, like water spiraling around a drain, in an effect called frame-dragging.
An amazing amount of work went into this experiment. There was a lot of serious doubt as to whether it would produce any measurable results. Apparently there is still some dispute about how precisely the theory has been confirmed. The satellite stopped functioning in 2005, and NASA shut the team down in 2008. So how is it that they suddenly have some results, in 2011? It sounds like a desperately attempt to justify their funding by reinterpreting some old data.

Einstein did not have much to do with this. He did not write any papers on frame-dragging, as far as I know. He did write a lot of papers on relativity, and frame-dragging uses relativity, but not the relativity that he contributed.
Gravity Probe B is one of the longest-running NASA projects ever. It started in 1963, ...

Physicist Clifford Will of Washington University in St. Louis, head of the external review board for Gravity Probe B, called the research team’s efforts “heroic” and stressed the importance of testing fundamental theories of nature, not just taking them for granted.

“It is popular lore that Einstein was right, but no such book is ever completely closed in science,” he said. “While the result in this case does support Einstein, it didn’t have
Will is a big Einstein idolizer.

Dennis Overbye at the NY Times explains:
Einstein’s theory relates gravity to the sagging of cosmic geometry under the influence of matter and energy, the way a sleeper makes a mattress sag. One consequence is that a massive spinning object like Earth should spin up the empty space around it, the way twirling the straw in a Frappuccino sets the drink and the whole Venti-size cup spinning around with it, an effect called frame dragging. Astronomers think this effect, although minuscule for Earth, could play a role in the black hole dynamos that power quasars.
Overbye is another Einstein idolizer. He wrote a whole biography of Einstein.

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