Trouton–Rankine experiment

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The Trouton-Rankine experiment was an experiment designed to measure if the Lorentz-FitzGerald contraction of an object according to one frame (the "preferred frame" defined by the Luminiferous aether) produced a measurable effect in the rest frame of the object. It was first performed by Frederick Thomas Trouton and Alexander Oliver Rankine.

Contents 1 Description 2 External links 3 See also 4 References

[edit] Description

The famous Michelson-Morley experiment of 1887 showed that the then accepted aether theory was not correct. FitzGerald and Lorentz, independent of each other proposed a contraction that would explain the null result of the Michelson Morley experiment. Lorentz showed that this contraction hypothesis along with what he referred to as "local time" made the Maxwell equations and Lorentz force law invariant to first order in a moving frame (he later expounded upon this to make Maxwell's equations perfectly invariant in a moving frame in agreement with special relativity).

Therefore in Lorentz ether theory and in Special Relativity, the Lorentz-FitzGerald contraction is not measurable in a co-moving frame. Trouton and Rankine however believed that if one frame saw a contraction of the object that it should be measurable in the object's rest frame. It was this effect that the experiment sought to measure.

Trouton together with A.O. Rankine set out to verify this in 1908 by attempting to measure the change of the resistance of a coil as they changed its orientation to the "aether velocity" (the velocity of the lab through the Luminiferous aether). This was done by putting four identical such coils in a Wheatstone bridge configuration which allowed them to precisely measure any change in resistance. The circuit was then rotated through 90 degrees about its axis as the resistance was measured. Because the Lorentz-FitzGerald contraction is only in the direction of motion, from the point of view of the "Aether frame" the length of the coils depended on their angle with respect to their Aether velocity. Trouton and A.O. Rankine therefore believed that the resistance as measured in the rest frame of the experiment should change as the device was rotated. However their careful measurements showed no change in resistance was detectable. ^[1]

This showed that if the Lorentz-FitzGerald contraction existed, that it was not measurable in the rest frame of the object.

This experiment has been re-enacted several times by Chase and Tomaschek ^{[2] [3] [4] [5] [6]} at a higher precision with the same results.

[edit] External links

• Trouton bio
• On the Electrodynamics of Moving Bodies Einstein's 1905 paper

[edit] See also

• Michelson-Morley experiment
• Lorentz ether theory
• Lorentz-FitzGerald contraction hypothesis

[edit] References

1. ^ Trouton F. T., Rankine A. (1908). "On the electrical resistance of moving matter". Proc. Roy. Soc. 80 (420). 
2. ^ Carl T. Chase (1927). "The Trouton-Noble Ether Drift Experiment". Phys. Rev. 30 (516): 516–519. 
3. ^ R. Tomaschek (1924). "The conduct of light of extraterrestrial light sources". Annalen der Physik 73: 105–126. 
4. ^ R. Tomaschek (1925). "Attempt at the locating of the electrodynamic effect of earth movements at high altitudes I". Annalen der Physik 78: 743–756. 
5. ^ R. Tomaschek (1926). "Concerning an experiment on the location of electrodynamic effects of the movement of the Earth at high altitudes II". Annalen der Physik 80: 509–514. 
6. ^ R. Tomaschek (1927). "Comments on my tests on the detection of electrodynamic effects at high altitudes". Annalen der Physik 84: 161–162.