Research On The Gravity Gradient In The Weak Equivalence Principle Based On The Torsion Pendulum

Weak equivalence principle is one of the basic hypotheses of Einstein general theory of relativity and all other theories of gravity. The WEP states bodies of different structure and compositions have the same ratio of gravitational mass to the inertial mass in uniform gravitational field. The methods testing the WEP usually are torsion pendulum and free falling, the latter one is limited by the height of experiment, so the sensitivity of this method can't be improved, thus nowadays the torsion pendulum is mostly used in high sensitivity experiment. With the development of modern technology, people can perform the test of WEP in space now. This thesis mainly calculate and analyze the effect of gravitational gradient based on the torsion pendulum, the result showed that for the modulated torsion pendulum, the torque caused by the gravitational gradient reached to 10^-12Nm, while the dissymmetry of round gravitational field can also affect the experiment. When we buildup the symmetry of measurement system and gravitational field around, the effect due to the gravitational gradient can be reduced much. We designed the relative experiment to verify the deduction, we use the modulated dumbbell torsion pendulum to test the WEP, and the result is accord with the deduction. We also simulate the environment of photon experiment, and calculate the effect by use of fourfold symmetry torsion pendulum, we find that the double frequency effect caused by gravitational gradient is reduced a magnitude when we buildup the symmetry of measurement system.