June 21, 2023 started, August 15 revised, January 15, 2024 revised. February 6 added, February 24, April 7, June 28, July 23, 2024, January 31, 2025, March 8, April 3, 2025 revised.
Takanori Senoh
0. Introduction
The Earth is rotating and revolving around the Sun. The Solar System is also said revolving in the Galaxy, following the Galaxy rotation. The whole Galaxy might be moving, too. Because everything around us is moving together with the Earth, we can't notice their motions. If there is something fixed, we can see the sum of all motions, which are affecting the Earth, by comparing us to it. Because the light has no weight, it is not affected by any other's motion and also it propagates even in a vacant space with the constant velocity of C= about 300,000(km/s) as the electro-magnetic wave. It can be a fixed index to the motion. Because the normal light spreads to 360 degrees all directions, to know the Earth motion, we have to reflect the light and make a fringe pattern. However, when the light is reflected, the Earth motion effect is almost canceled, and we have to measure a very small difference of about 10 billionth. If we use a laser beam, it doesn't spread and becomes a fixed index. Because the light source and the screen are moving together with the Earth, if the beam spot moves, it shows the motion of the Earth. Because the light speed C(m/s) is very fast, the time it returns by a mirror at L=1(m) away is just about T=7(ns). If the Earth motion is slow, we can't see the displacement of the beam spot. Because the Earth revolving speed V = about 30(km/s), which is 1/10,000 of the light speed C, the mirror moves 2/10,000 of the distance to the mirror L, about 0.2(mm), while the light returns.