题  目：Space Tests of General Relativity: Frame Dragging and Equivalence Principle

报告人：Prof. Ho Jung Paik

　　　　（Department of Physics,University of Maryland,College Park,Maryland,USA）

摘  要:  

  According to Einstein, a gyroscope in a 640-km polar orbit around the Earth is subject to two non-Newtonian precessions, a 6.6 arcsec/yr geodetic effect in the plane of the orbit and a 0.039 arcsec/yr frame-dragging effect due to the rotation of the Earth.  GP-B has now successfully observed both.  To measure these tiny effects has required developing a gyroscope 10⁷ times better than the best Earth-based inertial navigation gyroscopes and a reference telescope 10³ times better than any prior star tracker.  A unique combination of cryogenics and space technologies made this possible.

Presently, the most accurate limits on the Equivalence Principle (EP) come from ground experiments, with one part in 10¹³ at ³ 10⁴ km.  Significant improvements in the tests of the EP are expected from dedicated space-based experiments.  The low-g environment of space permits very soft superconducting magnetic suspension of the test masses.  The signal is detected by a sensitive superconducting differential accelerometer formed by the suspended test masses.  Combined with the full modulation of Earth’s gravity, an orbital mission promises a sensitivity of one part in 10¹⁸, five orders of magnitude improvement over the ground limits.

时  间：2010年5月25日（星期二）上午10:00

地  点：（北京西路2号）紫台大楼327教室

　　　　　　　　　　　　　　　　　　　　 紫金山天文台学术委员会学术交流工作委员会

　　　 　　　　　　　　　　　　　　　　　　　　　　　   2010年5月21日