man always interested in the nature of light, as evidenced by the myths and legends that have survived to our philosophical arguments and scientific observations.Light has always been an occasion for discussion of the ancient philosophers, and attempts were made to study it during the time of occurrence of Euclidean geometry - 300 BCIt was already known about the straightness of light, equal angles of incidence and reflection, the phenomenon of refraction of light, discussed the causes of the rainbow.Aristotle believed that the speed of light is infinite, and therefore, logically, and measurement of the speed of light is not negotiable.A typical case when the issue ahead of the era with its depth of understanding response.
few as 900 years ago, Avicenna suggested that no matter how big nor was the speed of light it is, after all, has a finite value.This opinion was not only him, but no one could prove it experimentally.Ingenious Galileo proposed an experiment mechanistic understanding of two people standing a few kilometers from each other, provide signals, opening the valve lantern.As soon as the second party to see the light from the lamp first, it opens its gate and the first participant records the time of receipt of the response of the light signal.Then the distance increases, and everything is repeated.It was expected to fix the increase in delays and on this basis to perform the calculation speed of light.The experiment ended in nothing, because "it was not sudden, but very quickly."
first measured the speed of light in 1676 the astronomer Ole Roemer - he took advantage of the opening of Galileo: the one discovered in 1609 four satellites of Jupiter, who in six months time difference between the two eclipses of the satellite is 1320 seconds.Using astronomical information of your time Roemer got the speed of light is 222,000 kilometers per second.Stunning was that the method of measurement is incredibly accurate - the use of the presently known data diameter of the orbits of the Earth, Jupiter, and the time lag dimming satellite gives the speed of light in vacuum, up to date values obtained by other methods.
first to experiments Remer had only one complaint - it was necessary to measure the earth means.It took almost 200 years and has built an ingenious Louis Fizeau apparatus in which a beam of light reflected from a mirror at a distance of more than 8 km long and come back.Fineness was that it took place on the way back and forth through the cavities of the gear, and if the rotation speed increases, the time will come when the light is not visible.The rest - a trick.The measurement result - 312,000 km per second.We now see that Fizeau was still closer to the truth.
The next step is to measure the speed of light did Foucault, who replaced the gear flat mirror.It is possible to reduce the dimensions of the plant and increase measurement accuracy up to 288,000 kilometers per second.Equally important has been done by Foucault and an experiment in which he determined the speed of light in the medium.For this purpose between the mirrors in the apparatus was placed pipe with water.In this experiment, it was found a reduction rate of light during its propagation in the medium depending on the refractive index.
In the second half of the 19th century, it is time to Michelson, who has devoted 40 years of his life in the field of light measurements.The climax of his work was the setting in which he measured the speed of light in a vacuum evacuated using a metal pipe length of more than one and a half kilometers.Another fundamental achievement Michelson was proof of the fact that for any wavelength of light speed in vacuum, and the same as a modern standard of 299792458 +/- 1.2 m / c.These measurements were carried out on the basis of the revised values of the reference meter, the definition of which was approved in 1983 as an international standard.
Wise Aristotle was wrong, but to prove it took almost 2,000 years.
