Experiment of Michelson-Morley

Albert A. Michelson and Edward Morley undertook an experiment of measurement of the difference of Speed of light between two perpendicular directions and at two periods separated by 6 months.

In fact, it is a whole series of experiments between 1881 (Michelson alone) and 1887 (together), date on which the result is definitively allowed: the ether does not exist. That also shows that the Speed of light is the same one in all the directions.

It is in the history of physics one of most important and one of the most famous experiments.

This experiment was conceived by Albert Abraham Michelson to measure speed of light in its supposed support (the ether) and while being based on the traditional law of addition speeds. It appeared that the Earth on its orbit with a Speed from approximately 30 km/s was the ideal laboratory to detect a variation speed of light on identical courses in length but which were to be different in time according to whether they would be in the direction of the movement or perpendicular to the wind of ether .

A famous comparison with the swimmer making an outward journey return in river having a current v makes it possible to include/understand the step of Michelson:

an outward journey and return in the direction of the river with like time t= $\ frac {L} {c-v} + \ frac {L} {c+v}$
or an outward journey return while crossing the river with t'= $2 \ frac {L} {\ sqrt {c^2-v^2}}$

the difference between these two times was to make it possible to have a delay of phase or dephasing and thus of the interference rings which were to move if one turned the whole of the interferometer in order to invert the two ways. The variation of awaited time was about 10^-12s.

Two measurements separated by 6 months make it possible to relative measure the possible contribution of the displacement of the solar system in its entirety the ether supposed.

The first interferometer assembled by Michelson not being precise enough, it is with Morley which finally the two researchers could affirm that the speed of the Earth compared to ether was null, and this constantly of the year.

This experiment is undoubtedly most famous of the negative experiments (giving a contrary result to what was required). Several attempts at traditional explanations failed and it is Ernst Mach which it first put forth the assumption that it was necessary to reject the concept of ether.

In parallel, of theoretical progress allowed, by the contraction lengths of Fitzgerald-Lorentz, to explain the experimental result, but it is finally what became the restricted Relativité of Einstein postulating the invariance of C which made it possible to explain astonishing it result by Michelson and Morley.

The Trouton-Noble experiment of is regarded as the equivalent in electrostatics of the experiment of Michelson and Morley.

See too

References

A.A. Michelson and E.W. Morley, Philosophies. Mag. S.5 , 24 (151): 449-463 (1887)
A.A. Michelson and Al , “Conference one the Michelson-Morley Experiment”, Astrophysical Newspaper 68,341 (1928)
Robert S. Shankland and Al , “New Analysis off the Interferometer Observations off Dayton C. Miller”, Reviews off Modern Physics , 27 (2): 167-178 (1955)

Simple: Michelson-Morley experiment

Random links:

Experiment of Michelson-Morley

See too

References

Related articles