We presented a new way to examine the principle of relativity of Special Relativity. According to the principle of relativity, the light dragging by moving media and the light propagation in stationary media with moving source and receiver should be two totally equivalent phenomena. We select a vacuum tube with two glass rods at two ends as the optical media. The length of the middle vacuum cell is L and the thicknesses of the glass rods with refractive index n are D1 and D2. The light drag effect of the moving vacuum tube with speed v is a first-order effect, delta t = 2(n-1)(D1+D2)v/c^2, which is independent of L because vacuum does not perform a drag effect. Predicted by the principle of relativity, the change of the light propagation time interval with stationary vacuum tube and moving source and receiver must be the same, i.e., delta tao = delta t = 2(n-1)(D1+D2)v/c^2. However all analyses have shown that the change of the propagation time interval delta tao is caused by the motion of the receiver during the light propagation in the vacuum tube. Thus, the contribution of the glass rods in delta tao is 2n(D1+D2)v/c^2, not 2(n-1)(D1+D2)v/c^2 in delta t. Importantly, the contribution of the vacuum cell in delta tao is 2Lv/c^2, not zero in delta t. Our analyses are solid in optics. The genuine tests of the prediction of the principle of relativity can be conducted by the experiments with two atomic clocks, or the experiments with fiber Sagnac interferometers.
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