Hammar experiment
Encyclopedia
The Hammar experiment was an experiment designed by Gustaf Wilhelm Hammar to test the aether drag hypothesis
.
, and later the Trouton-Rankine experiment
in 1908, presented (then) controversial evidence against the theory of a medium for light propagation known as the Luminiferous aether
; a theory that had been an established part of science for nearly one hundred years at the time. These experiments were inspired by the unexpected failure of the Michelson-Morley experiment
of 1887 to detect an expected aether wind of 30 km/s. These results cast doubts on what was then a very central assumption of modern science. In an attempt to explain the results of these experiments in the context of the assumed medium, aether, many new hypotheses were examined.
One of the proposals was that instead of passing through a static and unmoving aether, massive objects at the Earth's surface may drag some of the aether along with them, making it impossible to detect a "wind". Oliver Lodge was one of the first to perform a test of this theory by using massive lead blocks in an experiment that attempted to cause an asymmetrical aether wind. His tests yielded no appreciable results differing from previous tests for the aether wind.
More recently, Hammar re-enacted the MM experiment but with the addition of massive lead blocks on both sides of only one leg of the interferometer. It was performed with an intent - similar to Lodge's - of causing an asymmetry in any proposed aether wind.
Hammar's expectation of the results was that:
A) In an experiment without lead blocks, both arms would be equally affected by aether entrainment
.
B) In an experiment with lead blocks in place on one arm, only one arm would be affected by aether entrainment.
The reported result was that, even with the lead blocks in place, the fringe displacements were equal to the ones without any lead block. This was presented as proof against the aether drag hypothesis.
Aether drag hypothesis
In the 19th century, the theory of the luminiferous aether as the hypothetical medium for the propagation of light was widely discussed. An important part of this discussion was the question concerning the state of motion of Earth with respect to this medium. The aether drag hypothesis dealt with...
.
Overview
In 1903 the Trouton-Noble experimentTrouton-Noble experiment
The Trouton–Noble experiment attempted to detect motion of the Earth through the luminiferous aether, and was conducted in 1901–1903 by Frederick Thomas Trouton and H. R. Noble...
, and later the Trouton-Rankine experiment
Trouton-Rankine experiment
The Trouton–Rankine experiment was an experiment designed to measure if the Lorentz–FitzGerald contraction of an object according to one frame produced a measurable effect in the rest frame of the object, so that the ether would act as a "preferred frame"...
in 1908, presented (then) controversial evidence against the theory of a medium for light propagation known as the Luminiferous aether
Luminiferous aether
In the late 19th century, luminiferous aether or ether, meaning light-bearing aether, was the term used to describe a medium for the propagation of light....
; a theory that had been an established part of science for nearly one hundred years at the time. These experiments were inspired by the unexpected failure of the Michelson-Morley experiment
Michelson-Morley experiment
The Michelson–Morley experiment was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University in Cleveland, Ohio. Its results are generally considered to be the first strong evidence against the theory of a luminiferous ether and in favor of special...
of 1887 to detect an expected aether wind of 30 km/s. These results cast doubts on what was then a very central assumption of modern science. In an attempt to explain the results of these experiments in the context of the assumed medium, aether, many new hypotheses were examined.
One of the proposals was that instead of passing through a static and unmoving aether, massive objects at the Earth's surface may drag some of the aether along with them, making it impossible to detect a "wind". Oliver Lodge was one of the first to perform a test of this theory by using massive lead blocks in an experiment that attempted to cause an asymmetrical aether wind. His tests yielded no appreciable results differing from previous tests for the aether wind.
More recently, Hammar re-enacted the MM experiment but with the addition of massive lead blocks on both sides of only one leg of the interferometer. It was performed with an intent - similar to Lodge's - of causing an asymmetry in any proposed aether wind.
Hammar's expectation of the results was that:
A) In an experiment without lead blocks, both arms would be equally affected by aether entrainment
Entrainment
Entrainment may refer to:* Air entrainment, the intentional creation of tiny air bubbles in concrete* Brainwave entrainment, the practice of entraining one's brainwaves to a desired frequency...
.
B) In an experiment with lead blocks in place on one arm, only one arm would be affected by aether entrainment.
The reported result was that, even with the lead blocks in place, the fringe displacements were equal to the ones without any lead block. This was presented as proof against the aether drag hypothesis.
Interpretation
Because differing ideas of "aether drag" existed, the interpretation of the experiment can be done in the context of each version of the hypothesis.- None or partial entrainment by any object with mass. This was discussed by scientists such as Augustin-Jean FresnelAugustin-Jean FresnelAugustin-Jean Fresnel , was a French engineer who contributed significantly to the establishment of the theory of wave optics. Fresnel studied the behaviour of light both theoretically and experimentally....
and François AragoFrançois AragoFrançois Jean Dominique Arago , known simply as François Arago , was a French mathematician, physicist, astronomer and politician.-Early life and work:...
. It was refuted by the Michelson-Morley experimentMichelson-Morley experimentThe Michelson–Morley experiment was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University in Cleveland, Ohio. Its results are generally considered to be the first strong evidence against the theory of a luminiferous ether and in favor of special...
. - Complete entrainment within or in the vicinity of all masses. It was refuted by the Aberration of lightAberration of lightThe aberration of light is an astronomical phenomenon which produces an apparent motion of celestial objects about their real locations...
, Sagnac effectSagnac effectThe Sagnac effect , named after French physicist Georges Sagnac, is a phenomenon encountered in interferometry that is elicited by rotation. The Sagnac effect manifests itself in a setup called ring interferometry. A beam of light is split and the two beams are made to follow a trajectory in...
, Oliver Lodge's experiments, and Hammar's experiment. - Complete entrainment within or in the vicinity of only very large masses such as Earth. It was refuted by the Aberration of lightAberration of lightThe aberration of light is an astronomical phenomenon which produces an apparent motion of celestial objects about their real locations...
, Michelson–Gale–Pearson experiment.