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--------------------------------------- GP-B Scientists expect to announce the final results of the experiment in December 2007, following eight months of further data analysis and refinement. Today, Everitt and his team are poised to share what they have found so far — namely that the data from the GP-B gyroscopes clearly confirm Einstein's predicted geodetic effect to a precision of better than 1 percent. However, the frame-dragging effect is 170 times smaller than the geodetic effect, and Stanford scientists are still extracting its signature from the spacecraft data. The GP-B instrument has ample resolution to measure the frame-dragging effect precisely, but the team has discovered small torque and sensor effects that must be accurately modeled and removed from the result. "We anticipate that it will take about 8 more months of detailed data analysis to realize the full accuracy of the instrument and to reduce the measurement uncertainty from the 0.1 to 0.05 arc-seconds per year that we’ve achieved to date down to the expected final accuracy of better than 0.005 arc-seconds per year," says William Bencze, GP-B Program Manager. "Understanding the details of this science data is a bit like an archeological dig: a scientist starts with a bulldozer, follows with a shovel, and then he finally uses dental picks and toothbrushes to clear the dust away from the treasure. We are passing out the toothbrushes now." -------------------------------------------- The two discoveries Two important discoveries were made while analyzing the gyroscope data from the spacecraft: 1) the “polhode” motion of the gyroscopes damps out over time, and 2) the spin axes of the gyroscopes were affected by small classical torques. Both of these discoveries are symptoms of a single underlying cause: electrostatic patches on the surface of the rotor and housing. Patch effects in metal surfaces are well known in physics, and were carefully studied by the GP-B team during the design of the experiment to limit their effects. Though previously understood to be microscopic surface phenomena that would average to zero, the GP-B rotors show patches of sufficient size to measurably affect the gyroscopes’ spins. The gyroscope’s polhode motion is akin to the common "wobble" seen on a poorly thrown (American) football, though it shows up in a much different form for the ultra-spherical GP-B gyroscopes. While it was expected that this wobble would exhibit a constant pattern over the mission, it was found to slowly change due to minute energy dissipation from interactions of the rotor and housing electrostatic patches. The polhode wobble complicates the measurement of the relativity effects by putting a time-varying wobble signal into the data. The electrostatic patches also cause small torques on the gyroscopes, particularly when the space vehicle axis of symmetry is not aligned with the gyroscope spin axes. Torques cause the spin axis of the gyroscopes to change orientation, and in certain circumstances, this effect can look like the relativity signal GP-B measures. Fortunately, the drifts due to these torques has a precise geometrical relationship to the misalignment of the gyro spin/vehicle symmetry axis and can be removed from the data without directly affecting the relativity measurement. Both of these discoveries first had to be investigated, be precisely modeled and then be carefully checked against the experimental data before they are removed as sources of error. These additional investigations have added more than a year to the data analysis, and this work is still in process. To date, the team has made very good progress in this regard, according to its independent Science Advisory Committee, chaired by relativistic physicist Clifford Will of Washington University in St. Louis, Mo., that has been monitoring every aspect of GP-B for the past decade. ※※※※※※ 黄氏时空由光频多普勒红移定义可变时间单位秒t'=tsquart[(C-V)/(C+V)].时间秒的变化导致了可变光速C'=Csquart[(C-V)/(C+V)].光速的变化导致了可变距离单位米l'=lsquart[(C-V)/(C+V)].黄氏自旋衰变相互作用模型:引力=动量变化率，电磁力=角动量变化率.超光速C=2ZM/r |