Effects Of Rotating Gyroscopes Of Equivalence Principle Test For Extended Rotating Bodies

Equivalence principle (EP), as one of the fundamental hypotheses of Einstein's general relativity, has been tested by many experiments, including the torsion balance scheme and the free fall one. Current weak EP test comes to 10-13 by the rotating torsion balance and Lunar laser ranging methods. But the test of EP for rotating extended bodies, it is an opening question. A double free fall experiment to test the EP for rotating extended bodies has been performed by our group, and experimental result shows that the EP is still valid at the level of 1.67×10-7, which is mainly limited by the mechanical friction of the gyroscope. The limit could be improved by prolonging the effective free fall duration,thus then the EP test for rotating extended bodies with a torsion balance scheme is proposed. Based on it, I do some pre-study work for my master degree as follows: (1) The EP test for extended rotating bodies using a torsion balance is analyzed in detailed, especially discussion on the influence of spin-spin interaction between rotating gyroscope and Earth. And then preliminary experimental setup is constructed. (2) The magnetic field around the external rotating gyroscope is measured, which can be equal to electrifying rectangular loop. The magnetic torque from gyroscope's rotation and Earth's magnetic field on the torsion balance could come 3.6×10-12 N m along the fiber direction, and 3.6×10-11 N m perpendicular to the fiber with the frequency of the rotating gyroscope. (3) The internal friction torque between the rotor and stator of gyroscope is measured based on the angular moment law. The free angular velocity of the gyroscope is monitored by a optical sensor after running the gyroscope, and experimental result shows that the friction torque of the mechanical gyroscope is proportional to its rotating angular speed, and comes to about 10-4 N m as its angular speed is about 17000 rpm. In additional, according improvement to reduce the effect of gyroscope rotating is briefly discussed in the end. This work is partially supported by the National Project for the Development of Key Fundamental Science in China (2003CB716305), and the National Natural Science Foundation of China (NSFC:10121503).