If you never read about the Michaelson-Morley experiment, then it’s about time to read our article and learn all about the Michaelson-Morley experiment and speed of light!
What is the Michaelson-Morley experiment?
At the beginning of the 19th century, it was assumed that light waves were electromagnetic in nature. However, if this was the case, a challenging question arose due to the fact that radiation was not known without specifying a material means of propagation: how could light be transmitted through a vacuum? Where can none of these particles be found?
People wanted answers to those questions, and the Michaelson-Morley experiment should have brought them new insights and knowledge about light and the speed of light.
As a potential remedy, it was proposed that there is a new substance, and that if the inferences that this fictitious substance was able to draw from observations were confirmed by experimentation, then this new substance’s existence would also be established.
On the contrary, there was nothing like that. Although this simple explanation of how light travels in a vacuum was a significant step in the development of science in this direction, it did not provide an acceptable answer at the time.
This material was given the name ether, and it was believed to possess ideal properties such as zero density, a high degree of flexibility, and complete transparency. In scientific speculation, the aether was thought to fill all of the space that was now known, and because of this, it was considered to be an excellent absolute reference system against which all else was computed.
There is not the smallest question that the interplanetary and interstellar regions are inhabited by a material substance or body which is undoubtedly the biggest and perhaps the most uniform in existence, as Maxwell said in the Encyclopaedia Britannica when he was fully convinced of its existence.
On the other hand, recent research has demonstrated that the region in between star bodies consists of nothing more than empty space.
If the ether did exist and was used as an absolute reference system, the Earth would move with respect to it at a speed (v) that would influence the calculation of the speed of light (c) in the same way that the speed of one car influences the perception of the speed of the other car from the first car:
Assuming that an object traveled in the same direction as light, the speed of the object would be calculated as follows for an observer stationed on Earth: c»=cv
If an observer on Earth were to assume that an object was moving in the opposite direction to that of light, the speed of the object would be calculated as follows: c»»=c+v.
When did the Michaelson-Morley experiment took place?
In 1887, Albert A. Michelson and Edward W. Morley carried out a series of tests that demonstrated there is only one speed of light. These results were the result of their work.
The speed of light in a vacuum remains the same in all inertial frames, unaffected by the relative velocity of the light’s source and the observer.
As a result, the presence of the ether does not have any significance in the physical world.
The Michaelson-Morley experiment begins in 1931, when the former develops an interferometer (shown), which has one branch that is perpendicular to the direction in which the Earth is moving, and the other branch that is parallel to the direction in which the Earth is moving.
What did the Michaelson-Morley experiment find out?
The experiment involved pointing a light beam at a half-silvered mirror, M, that was tilted at a 45-degree angle to act as a splitter. This meant that half of the light reflected towards E 2 and the other half passed through it to reach E 1.
This caused the entire system to move in the direction of the Earth’s motion at a speed of 30 kilometers per second (the speed at which the Earth orbits the sun).
After that, the beams interfered with the mirrors located at the ends of the branches before returning to the center of the structure. They were now on their way to the telescope, which collected the beams from both mirrors as they interfered with each other after traveling through the same levels of air and glass thickness.
The fact that the system moves together with the motion of the Earth means that E 2 is at a different place at various times. This causes the amount of time it takes for a beam to go to E 2 and back (t 2) to be distinct from the amount of time it takes for the beam to travel to E 2.
t 1 =2l/c 1/(1-(v 2 /c 2)) and t 2 =2l/c 1/√(1-(v 2 /c 2))
This time difference ought to be represented in the interference figure that can be seen in the telescope if what was expected to happen turns out to be true. On the contrary, there was nothing like that. Michelson and Morley ran the Michaelson-Morley experiment again in 1887, and the findings were the same.
They either flipped the roles of the axis so that the mirrors performed the opposite role, or they took further precautions to ensure that the system was not affected by any forces from the outside. Either the results were negative once more or they were positive for further investigation.
To confirm that the principles of electromagnetism were right and that the speed of light is the same in all inertial frames, independent of the speed of the source and the observer (299,792.458 kilometers per second), several further possibilities were examined and then eliminated. In the future, Albert Einstein would base his studies on relativity on this foundation.