  One of the widespread confusions concerning the history of the 1887
Michelson-Morley experiment has to do with the initial explanation of this
celebrated null result due independently to FitzGerald and Lorentz. In neither
case was a strict, longitudinal length contraction hypothesis invoked, as is
commonly supposed. Lorentz postulated, particularly in 1895, any one of a
certain family of possible deformation effects for rigid bodies in motion,
including purely transverse alteration, and expansion as well as contraction;
FitzGerald may well have had the same family in mind. A careful analysis of the
Michelson-Morley experiment (which reveals a number of serious inadequacies in
many text-book treatments) indeed shows that strict contraction is not
required.
