Some have challenged the validity of the equivalence principle by considering the effects of rotation. A “sufficiently small” region of spacetime for transforming away the translatory motion of an object to some degree of approximation may not be sufficiently small for transforming away the rotational motion to the same degree of accuracy, but this does not conflict with the equivalence principle; it simply means that for an infinitesimal particle in a rotating body the “sufficiently small” region of spacetime is generally much smaller than for a particle in a non-rotating body, because it must be limited to a small arc of angular travel. In general, all such arguments against the validity of the (local) equivalence principle are misguided, based on a failure to correctly limit the extent of the subject region of space and time.
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