Trouton–Rankine experiment

FitzGerald and Lorentz, independently of each other, proposed a length contraction of the experimental apparatus in the direction of motion (with respect to the luminiferous aether) that would explain the almost null result of the Michelson–Morley experiment.

According to Trouton's view of electrodynamics, the calculations then predicted a measurable effect of the length contraction in the lab frame.

This was done by putting four identical coils in a Wheatstone bridge configuration which allowed them to precisely measure any change in resistance.

Trouton and Rankine therefore believed that the resistance as measured in the rest frame of the experiment should change as the device was rotated.

[1][2] This showed that if the Lorentz–FitzGerald contraction existed, it was not measurable in the rest frame of the object – only theories containing the complete Lorentz transformation, like special relativity, are still valid.

In the Trouton–Rankine experiment, it was expected that length changes due to Lorentz–FitzGerald contraction would result in detectable changes in the measured voltage across a Wheatstone bridge as the circuit is rotated.