The famous and ingenious Michelson experiment in 1881 was stimulated by a suggestion of C. Maxwell in 1879. Maxwell believed in the existence of the aether and was eager to find out the earth's motion through the aether. In his letter to Todd of the U.S. Nautical Almanac Office (Washington), Maxwell suggested a terrestrial experiment on the (2-way) speed of light, since the (first order) effect related to the eclipses of Jupter's moon was very difficult to observe, as pointed out by Todd. Maxwell said that the effect due to the earth's motion in terrestrial experiments is of the second order v2/c2 ∼ 10−8, which would be too small to observed. Fortunately, Maxwell's letter to Todd was also read by Michelson (a young naval instructor.) Michelson was, however, not deterred by the difficulty and, two years later, came up with an ingenious device (the Michelson interferometer) with unprecedented sensitivity to measure this very small second order effect…（4）