During the period of 1887, (who later became the first Nobel Prize winner in physics in the United States) and Edward Morley conducted a very detailed experiment at Cass College of Applied Science in Cleveland. The purpose is to measure the speed of the earth in the ether (that is, the speed of the ether wind).

If ether exists, and the propagation of light speed in ether follows Galileo's principle of velocity superposition:

Assuming that the ether is stationary relative to the sun, the instrument moves to the right at the orbital speed relative to the ether in the experimental coordinate system. The light emitted by the light source is split into two beams by the spectroscope, and the beam 1 is reflected by the mirror m 1 and projected onto the observation screen by the spectroscope. The beam 2 is reflected by the m 2 mirror and projected onto the observation screen through the beam splitter, which interferes with the beam 1. The speed of light in the ether is zero, and the speed of the earth relative to the ether is zero. The propagation speeds of the beam 1 arriving at M 1 and returning from m 1 are different, and the time required to complete a round trip is: the time required for the beam 2 to complete a round trip is, and the optical path difference between the beam 2 and the beam 1 arriving at the observation screen is.

Then the experimental instrument is rotated by 90 degrees, so that the time when the light beam 1 and the light beam 2 arrive at the observation screen is exchanged, and the interference fringes that have been formed are moved. The amount of small change is. The number of stripes moved is.

Sodium light source was used in the experiment;

The orbital motion rate of the earth is: the optical arm of the interferometer (beam splitter to reflector),

The strip that should be moved is:. Michelson and Morey installed the interferometer on a very smooth marble, and let the marble float on the mercury tank, which can rotate smoothly. When the whole instrument rotates slowly, the reading is continuous. At this time, the accuracy of the instrument is 0.0 1%, that is,1100 fringe movements can be detected. It should be easy to measure the fringe movement with this instrument. Michelson and Morey assume that if the instrument is rotated by 90, the time difference of light passing through OM 1 and OM2 should change and the interference fringes should move. By measuring the distance of fringe movement from the experiment, we can calculate the speed of the earth relative to the ether, thus confirming the existence of the ether. But the experimental results show that no fringe movement is found. Many years later, the Michelson-Morey experiment was repeated many times, and the results were all zero.

More information can be paid attention to? Michelson-Morey experiment