Pendulum used in formal experiment. The 1# left-handed crystal connects with 2# right-handed crystal by the 1# short rod and 3# short rod, and 2# left-handed crystal connects with 1# right-handed crystal by the 2# short rod and 4# short rod. Four short rods are fixed on the long rod, and the whole pendulum is suspended from an air-bearing turntable by a tungsten fiber.