How was the speed of light measured and what is its real value

<pre>How was the speed of light measured and what is its real value

Long before scientists measured the speed of light, they had to work hard to define the very concept of “light.” One of the first to think about this was Aristotle, who considered light to be some kind of mobile substance that spreads in space. His ancient Roman colleague and follower Lucretius Car insisted on the atomic structure of light.

By the seventeenth century, two basic theories of the nature of light-corpuscular and wave-were formed. The first was Newton. In his opinion, all light sources emit the tiniest particles. In the process of “flight” they form luminous lines – rays. His opponent, the Dutch scientist Christian Huygens, insisted that light is a kind of wave movement.

As a result of centuries of controversy, scientists came to a consensus: both theories have the right to life, and light is the visible spectrum of electromagnetic waves.

A bit of history. How the speed of light was measured

Most scientists of antiquity were convinced that the speed of light is infinite. However, the results of the studies of Galileo and Hooke allowed its extreme, which was clearly confirmed in the 17th century by the outstanding Danish astronomer and mathematician Olaf Remer.

His first measurements he made, watching the eclipses of Io – the satellite of Jupiter at a time when Jupiter and Earth were located on opposite sides of the sun. Remer noted that as the Earth moved away from Jupiter by a distance equal to the diameter of the Earth's orbit, the delay time varied. The maximum value was 22 minutes. As a result of calculations, he got a speed of 220,000 km / sec.

After 50 years in 1728, thanks to the discovery of aberration, the English astronomer J. Bradley “clarified” this figure to 308,000 km / sec. Later the speed of light was measured by the French astrophysicists François Argo and Leon Foucault, having received 298,000 km / s at the exit. An even more accurate measurement technique was suggested by the creator of the interferometer, the famous American physicist Albert Michelson.

Michelson's experience in determining the speed of light

The experiments continued from 1924 to 1927 and consisted of 5 series of observations. The essence of the experiment was as follows. A light source, a mirror and a revolving octagonal prism were installed on Mount Wilson in the vicinity of Los Angeles, and a reflecting mirror in 35 km on Mount San Antonio. Initially, the light through the lens and the slit hit the rotating prism using a high-speed rotor (at a speed of 528 r / s).

Participants in the experiments could adjust the speed of rotation so that the image of the light source was clearly visible in the eyepiece. Since the distance between the vertices and the rotation frequency were known, Michelson determined the magnitude of the speed of light – 299796 km / sec.

Finally, at the speed of light, scientists were defined in the second half of the 20th century, when masers and lasers were created, characterized by the highest stability of the radiation frequency. By the early 1970s, the error in measurements decreased to 1 km / sec. As a result, on the recommendation of the XV General Conference on Weights and Measures, held in 1975, it was decided that the speed of light in a vacuum is now 299792.448 km / sec.

Is the speed of light achievable for us?

Obviously, the development of the far corners of the universe is inconceivable without spacecraft flying at great speed. It is desirable with the speed of light. But is it possible?

The barrier of light speed is one of the consequences of the theory of relativity. As you know, increasing speed requires increasing energy. The speed of light will require almost infinite energy.

Alas, but the laws of physics are categorically against it. At a speed of a spacecraft at 300,000 km / s, particles flying towards it, for example, hydrogen atoms are transformed into a deadly source of powerful radiation equal to 10,000 sievert / s. It's about the same as being inside the Large Hadron Collider.

According to scientists at Johns Hopkins University, while in nature there is no adequate protection against such monstrous cosmic radiation. Completes the destruction of the ship erosion from the effects of interstellar dust.

Another problem of light speed is slowing down time. Old age will become much longer. The visual field will also undergo a curvature, as a result of which the trajectory of the ship will pass as it were inside the tunnel, at the end of which the crew will see a radiant flash. Behind the ship remains absolute pitch darkness.

So in the near future, humanity will have to limit its rapid “appetites” 10% of the speed of light. This means that the nearest star to the Earth, Proxima Centauri (4.22 light years), will have to fly about 40 years.

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