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Gentlemen, Start Your Gyros - Gravity Probe B Ready

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odysseus145

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Gentlemen, Start Your Gyros<br /> 09.02.04 <br /><br /><br />NASA's Gravity Probe B spacecraft has begun its search for a bizarre prediction of Einstein's relativity. <br />It's "all systems go" for one of the most ambitious physics experiments ever attempted.<br /><br /> <br />On August 27th, after four months in orbit, NASA's Gravity Probe B satellite began its year-long hunt for signs of a subtle space-time vortex around Earth predicted by Einstein's theory of relativity. The search isn't going to be easy, but for scientists involved, one of the hardest parts is already over: months of delicately starting up and checking out the satellite, when one wrong move could have ruined the experiment before it ever got started. <br /><br />"It's a long and tortuous story," says Francis Everitt, principal investigator for Gravity Probe B (GP-B) and a professor at Stanford University.<br /><br />One of the key parts of GP-B is an onboard telescope that locks on to the star IM Pegasus, which serves as a fixed point of reference in the sky. Everitt and his colleagues had figured that pointing the telescope at that star would be quick and painless, taking only three days after the launch. <br /><br />Instead it took weeks.<br /><br />First, sunlight reflecting off floating dust particles confused the satellite's star-tracking sensors. These sensors use the locations of constellations to orient the spacecraft, and the tiny shining specs looked like stars. The dust eventually cleared, but then another problem arose: Cosmic radiation in the form of high-speed protons peppered the telescope's light sensor, causing false signals. Mission scientists had to tweak the satellite's software to ignore these pulses. And on it went like this for weeks; scientists would solve one problem only to encounter another. <br /><br />"Now it has become very routine, and we only take about a minute to acquire the star as we come up over the horizon," Everitt says. (The satellite loses sight of the guide star during <div class="Discussion_UserSignature"> </div>
 
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wvbraun

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Great! Gravity Probe B is definetely one of the more interesting science missions. I think it's really incredible that mankind has come this far (regarding science): We're able to observe the distortion of space-time itself!
 
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mrmorris

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<font color="yellow">"Hypothetically speaking, if it can disprove relativity..."</font><br /><br />It cannot disprove relativity. At best it can either provide additional evidence in regards to Albert's predictions or it can *not* provide that evidence. <b>Not</b> providing the evidence isn't even tantamount to an argument against relativity, because then you enter into the question of whether the experiment itself is sound and that the hardware is 100% functional, etc.<br /><br />Most of Einstens predictions involving relativity have been supported by real-world experimentation. Frame-dragging is one of the few (or the only?) prediction that has not been tested. GPB might provide evidence to support it -- or it might not. Whichever it does -- some scientists will likely argue the results are valid -- and others will argue they are not. After all -- how much faith can you put into results derived from crystal balls -- however perfectly spherical they might be?
 
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zavvy

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<b>Neutron Stars Steal Space Probe's Glory </b><br /><br />LINK<br /><br /> <br />It has taken almost 50 years to conceive and build and has cost more than $700 million, but now NASA's Gravity Probe B spacecraft could be upstaged by telescopes on the ground. <br /><br />The craft is designed to accurately test Einstein's general theory of relativity. According to the theory, a gyroscope orbiting a massive object such as the Earth should experience two forces that gradually cause it to "precess", pushing its axis of spin out of alignment. <br /><br />The stronger force, known as the geodetic effect, is caused by the Earth warping the fabric of space-time. The other, known as the gravitomagnetic effect, is caused by the rotating Earth dragging space and time around with it. <br /><br />Gravity Probe B, which carries ultra-sensitive gyroscopes, was conceived in the 1950s to measure these forces, but was only launched in April 2004. It has yet to take any measurements. Francis Everitt, the physicist in charge of the project at Stanford University, US, says the probe should produce results by mid-2006. <br /><br /><br />Binary pulsars <br /><br /><br />Meanwhile, astronomers have been studying binary pulsars - two rapidly spinning neutron stars orbiting each other - to measure these effects. The gravitational fields of pulsars are so strong that both of the forces predicted by Einstein should show up relatively clearly in the precession of each pulsar in a binary system, much like that in a gyroscope. <br /><br />Last week, Ingrid Stairs of the University of British Columbia in Vancouver, Canada, and colleagues reported for the first time that the observed precession in a binary pulsar due to the geodetic effect was consistent with that predicted by general relativity. <br /><br />So the big prize for Gravity Probe B is now the gravitomagnetic effect, which is hundreds of times weaker than the geodetic effect
 
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