The FitzGerald-Lorentz contraction hypothesis

1889-1892 Light and sky theory

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A hypothesis by which bodies contract along the direction of motion through the ether. An ad hoc device that rescued a stationary ether from the experiment that showed its absence.

Contraction was suggested in 1889 by the Irishman George FitzGerald; independently in 1892 the Dutchman Hendrik Lorentz reached the same idea. This preserved the stationary ether for another decade and a half.

Along the way the theory supplied the mathematical apparatus (the Lorentz transformations) that Einstein reinterpreted in 1905, but by then without the ether.

Why this date

exact

Links under review

• The Michelson-Morley experiment

  influenced · Confidence: high

  The first half of this link is supported verbatim by FitzGerald's letter of 1889. Lorentz's independent arrival in 1892 comes from a summary in the Wikipedia article; a verbatim quotation is needed from Lorentz H. A., «De relatieve beweging van de aarde en den aether», 1892, or from Miller A. I., «Albert Einstein's Special Theory of Relativity», 1981.

  The contraction hypothesis was put forward specifically to explain the null result.

  Link sources

  • FitzGerald G. F. «The Ether and the Earth's Atmosphere», Science 13 (328), 390 (1889) Verified 20 Sep 2026

    I have read with much interest Messrs. Michelson and Morley's wonderfully delicate experiment attempting to decide the important question as to how far the ether is carried along by the earth. Their result seems opposed to other experiments showing that the ether in the air can be carried along only to an inappreciable extent. I would suggest that almost the only hypothesis that can reconcile this opposition is that the length of material bodies changes, according as they are moving through the ether or across it, by an amount depending on the square of the ratio of their velocity to that of light.

  • Wikipedia «History of special relativity» (2024) Verified 20 Sep 2026, quotation assembled from fragments

    FitzGerald (1889) offered another explanation of the negative result of the Michelson-Morley experiment ... material bodies would contract in the line of motion (length contraction). ... Also Lorentz (1892b) proposed length contraction independently from FitzGerald in order to explain the Michelson-Morley experiment.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.

• Special theory of relativity ("Zur Elektrodynamik bewegter Körper")

  influenced · Confidence: medium

  The only source speaks of Einstein's acquaintance with Lorentz's 1895 treatment of the Fizeau experiment, not of his taking over the transformations; a historical study is needed (Miller 1981, Stachel).

  The Lorentz transformations gave Einstein the mathematical apparatus that he derived from two postulates without an ether.

  Dispute: The quotation confirms Einstein's acquaintance with Lorentz 1895 but gives no direct statement about borrowing the transformations; for reliability a reference to Miller A. I. "Albert Einstein's Special Theory of Relativity" (1981) or Stachel (1982) should be added.

  Link sources

  • Weinstein G., arXiv:1204.3390 (2012) Verified 20 Sep 2026

    According to the 1922 Kyoto lecture notes, before 1905 Einstein tried to discuss Fizeau's experiment 'as originally discussed by Lorentz' (in 1895).

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Node sources

• FitzGerald G. F. «The Ether and the Earth's Atmosphere», Science 13 (328), 390 (1889) Verified 20 Sep 2026

  I would suggest that almost the only hypothesis that can reconcile this opposition is that the length of material bodies changes, according as they are moving through the ether or across it, by an amount depending on the square of the ratio of their velocity to that of light.

"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Further reading

Not evidence: these carry no quotation and support nothing we wrote. They are books and scans to read next.

• Wikipedia «History of special relativity» (2024)

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