# Were there doubts that Voigt's time dilation was correct rather than Einstein's?

According to Wikipedia's Voigt transformation:

Lorentz did not adopt this transformation, as he found in 1904 that only the Lorentz contraction corresponds to the principle of relativity. Since Voigt's transformation preserves the speed of light in all frames, the Michelson–Morley experiment and the Kennedy–Thorndike experiment can not distinguish between the two transformations. The crucial question is the issue of time dilation. The experimental measurement of time dilation by Ives and Stillwell (1938) and others settled the issue in favor of the Lorentz transformation.

Einstein derived the Lorentz transformation using the two postulates, see Einstein’s Postulates and the Lorentz Transformations by Terletskii. Einstein also derived the equations for transverse and longitudinal mass and in the derivation time dilation equation was used. I'm a beginner and just trying to understand the relativity at basic level.

If both Einstein's and Lorentz's derivations were the same then wouldn't it mean that Voigt's time dilation equation had more chance of being wrong? If it was not decided until the experiment of Ives and Stillwell that which version of time dilation equation was right then it would also mean that though Einstein postulates were correct but still until 1938 there was still some doubt regarding some quantitative results derived by Einstein. In other words, if Voigt's time dilation was found correct, how would it have affected the other quantitative results or formulas?

I'd really appreciate if you could help me with it. I'm posting it here because IMHO it has more to do with the history.

• @PG1995 It is a nice paper. As the author points out on p.10, while the wave equation is invariant under the Voigt's transformations the d'Alembert operator ◻ is not, so they do break the principle of relativity. Form-invariance will not be preserved if we put something other than $0$ into the right hand side of the equation. Thus, Voigt's "second postulate" was weaker than Einstein's. It was known that Maxwell's electrodynamics was not form-invariant under Galilean transformations, but that was to be expected since the ether frame is privileged. – Conifold Apr 10 at 9:01