Michelson's experiments.

Measuring the speed of light.

Michelson has three such major experiences:

1. Experience in determining the own speed of propagation of light. Just wanting to digitally capture the speed of light.

2. Receive answer to the question: does ether exist?

3. Experience has shown that the speed of movement of light does not depend on the speed of movement of the source, which produces (generates) this light.

I'll tell you about these experiences as simply as possible.

The experiment in determining the speed of light is very simple. The speed of anything, except for some virtual particles of quantum mechanics, is determined elementarily from the formula: s = vt . Knowing the distance and time, we will determine the speed. Michelson built something like this.

It works like this. A ray of light from a light source falls on mirror 1 at point h of an octahedral drum along line a and is reflected along line b. It must be remembered that the angle of incidence of the beam is equal to the angle of reflection. Beam b reaches the mirror and is reflected at point m, then hits the mirror 1 at point g. And from here it gets to point n on the screen. If you turn the drum a little along the arrow, then the angle between rays a and b will decrease slightly and ray b will hit on the mirror not at point m, but let's say at point k. Now the reflected ray d will also fall not to point g, but to some other point, for example, p.

If we turn the wheel against the drawn arrow, then the ray that has traveled all the way will hit some other point on the other side of point n.

If, during the time the ray moves from point h to point g, we could replace mirror 1 with mirror 2 and so on, the picture on the screen would not change. This replacement of mirrors can be done with the appropriate drum rotation speed. But this is a primitive scheme of the device and in it, at any speed of rotation of the reels, we will see a continuous light line on the screen.

To avoid this, the beam of light must be cut into pieces. At a time when the mirror of the drum is in a position where the beam can travel exactly along the path indicated in the figure, and the beam should be launched, and then immediately cut off (blocking the path to the light). The shorter the beam, the less blurry the spot on the screen will be, and of course the paler. Now, at the corresponding drum revolutions, we will see a spot on the screen that can move across the screen in one direction or another when the drum revolutions change. Based on the number of revolutions of the drum, we can calculate the time to replace mirror 1 with mirror 2.

Let's measure the path from point h to point m. That's all: there is time, there is distance, you can calculate the speed.

Therefore, in reality, Michelson's installation was structured like this:

The entire installation was on Mount Wilson, and the reflection mirror was on Mount San Antonio at a distance of 35 km. The slit cut the beam, and instead of the drum, an octahedral prism was used. In this experiment, Michelson received the speed of light - 299796 km/s. But that was not all. This was obtained by speed in the air. And air is not a very constant environment. And the pressure is different, and the temperature, and humidity, and dust, and what is there just not. It was necessary to determine the speed of light in a vacuum.

Already a rather old Michelson was given money, he made a pipe about a mile long, put mirrors in it, so that the beam path was about 8 miles, pumped air out of the pipe and launched his device. As a result, he received the speed of light in a vacuum of 299774 km/s.

Modern studies using masers and lasers have shown that the speed of light is 299792.458 km/s. We live with this.

Michelson's experiment in detecting ether and proof of the independence of the speed of light from its source.

If we accept that our space is filled with something material in the form of air, water or some small substrate, which we cannot even feel, then the propagation of electromagnetic waves will appear as vibrations of this substrate, like water or air molecules.

Probably, many have observed this phenomenon. When you stand on the platform waiting for the train, you can see the following. Usually the train, which does not stop at this platform, starts giving a signal in advance. And at first you hear a high signal, like and-and-and ..., and when the train passes the platform, you hear a low oo-oo ... It turned out like this: the whistle generated in both cases the same frequency. He did not begin to change his tone, then squeak, then hum. The waves were the same, but from the approaching train they flew faster than you, as if something pushed them, and when the train passed the platform this spring (wave) seemed to be holding back.

Michelson wanted to see something similar with light. He came up with an interferometer device. Its scheme is very simple.

Light a from a source falls on a semitransparent mirror, where it is divided into two beams c and b. These rays reach their mirrors and are reflected as d and e rays, which then return to the translucent mirror. Beam d passes directly onto the screen, and beam e, reflected from the translucent mirror, also hits the screen. Both of them will create an interference image on the screen.

This interferometer was placed on a heavy stone slab that floated in a mercury bath and could be rotated without disturbing its geometric proportions. It was installed on the ground like this.

The Earth moved around the Sun at the speed of vEarth. The ethereal wind blew on the device at a speed of vaire. The light source was emitting light at a speed of c. This is the whistle of the electric train. In this position of the interferometer, the speed of light and the speed of the ether were summed up, and the total speed of light was equal to c + vether. There was some kind of picture on the screen.

Then they took and turned the interferometer 180 degrees. Now the total speed of light should be equal to the value of c - vether. The picture should have changed. But it turned out that she barely changed. Why? After all, it should have changed. At the time, they believed in ether. And, finally, they came up with: after all, the Earth is moving and its speed compensates, exactly, the speed of the ether wind. And there is nothing to add to or subtract from the speed of light.

Perhaps this case was in the spring. They measured everything well and fixed it. They especially remembered that the Earth flew against the etheric wind. We waited for the autumn, when the Earth should fly after the etheric wind, and moreover, it was at the same distance from the Sun, as in the spring, so that the speeds were equal. Now the speed of the Earth was not subtracted from the speed of the ether wind, but, on the contrary, was added to it, making it stronger. In this case, when carrying out the same experiment as was done in the spring, the picture should have changed even more.

But there were no changes in the picture either at different reversals or at any time of the year. So they decided: there is no ether and the speed of light does not depend on its source. It spreads itself according to its own laws.

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