NASA's Gravity Probe B Confirms Two Einstein Space-Time Theories

[n2doc]

ScienceDaily (May 4, 2011) — NASA's Gravity Probe B (GP-B) mission has confirmed two key predictions derived from Albert Einstein's general theory of relativity, which the spacecraft was designed to test.

The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates.

GP-B determined both effects with unprecedented precision by pointing at a single star, IM Pegasi, while in a polar orbit around Earth. If gravity did not affect space and time, GP-B's gyroscopes would point in the same direction forever while in orbit. But in confirmation of Einstein's theories, the gyroscopes experienced measurable, minute changes in the direction of their spin, while Earth's gravity pulled at them.

The findings are online in the journal Physical Review Letters.

"Imagine the Earth as if it were immersed in honey. As the planet rotates, the honey around it would swirl, and it's the same with space and time," said Francis Everitt, GP-B principal investigator at Stanford University. "GP-B confirmed two of the most profound predictions of Einstein's universe, having far-reaching implications across astrophysics research. Likewise, the decades of technological innovation behind the mission will have a lasting legacy on Earth and in space."

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http://www.sciencedaily.com/releases/2011/05/110504150655.htm

[ewagner]

1. for a nerd like me...

this is really exciting....

[girl gone mad]

2. k & r

Relativity is still as robust as ever.

[ewagner]

3. So where is

the link between Relativity and Quantum Mechanics???

(taps foot and asks Scientific Community) "I'm waiting......"

[somone]

4. Seems overhyped and overpriced:

http://news.sciencemag.org/sciencenow/2011/05/at-long-last-gravity-probe-b.html

...Other researchers, however, greeted the results with what amounted to polite applause. Gravity Probe B fell well short of the precision developers had hoped to achieve in making the key measurement. Moreover, the project got scooped 6 years ago, when two physicists made a similar measurement using data from much cheaper satellites...

Some other scientists aren't sure how much they trust the corrections. Five years ago, Ciufolini notes, Gravity Probe B researchers were reporting uncertainties more than 10 times bigger. Correcting for such large "systematic errors" is tricky business, he says: "I don't know the details, but it seems to me very difficult to get rid of more than 90% of the systematic error."

The previous measurement also puts a damper on the new results. In 2004, Cifuolini and Erricos Pavlis of University of Maryland, Baltimore County, measured frame dragging by tracking the orbits of the LAGEOS and LAGEOS II satellites, simple reflectors launched in 1976 and 1992 and used primarily to monitor the motion of Earth's surface. By very carefully monitoring which way the planes of the satellites' orbits turned or "precessed," they measured the effect to 10% accuracy, largely stealing the thunder of the Gravity Probe B team in some researchers' opinions. "At best they've just confirmed the work Ciufolini did," says Robert O'Connell, a theorist at Louisiana State University in Baton Rouge. "So I find it a bit too much, all the hoopla" of a NASA press conference, he says.

In the end, Gravity Probe B's full value goes beyond the results of the experiment, Everitt told Science. "Why was it worth it?" he says. "Just the element of challenge in it, the element of invention in it. There was this constant challenge of inventing new technologies." He notes that 100 students earned Ph.D.s working on the experiment. Others offer a less favorable assessment. "This <$760 million> was government money," O'Connell says. "And to my mind it was misspent and poorly managed" by the government agencies involved...