compressed-aprendendo ciencia e sobre a sua natureza

ether. Realizing this effect’s impact on time measurements, he advanced a notion of “local
time” (t’) and applied it to bodies moving in the ether, which Lorentz thought was totally
immobile. For an observer moving with respect to the ether, he reasoned, the time locally
noticeable to him was a function of the time variable (t) for a reference frame at rest in the
ether and the observer’s speed (v) relative to the latter: t' = t − vx/c 2 . Lorentz used this idea to
explain Fizeau’s measurements of the Fresnel’s drag coefficients for moving liquids, and such
phenomena as light aberration and the Doppler Effect. In this Lorentz used a synchronization
formula similar to the one Einstein would offer in his paper on Special Relativity. Subsequent
applications of Lorentz’s theory led to stimulating results; e.g. for the frequency of oscillating
electrons he derived what we now call its “Lorentz transformation” between a reference
frame at rest in the ether and a “moving” frame. According to Lorentz, however, the attending
notion of time transformation in the context of relative motion was of heuristic value only; in
his view, only clocks at rest in the ether showed “true time.” Early in the new century,
however, it became clear that Lorentz’s local-time explained the negative results yielded by
experiments designed to verify the ether drift, but only to first order in v/c; other negative
result experiments required modifications that included second-order effects. Lorentz (1904)
responded to the challenge by proposing that all forces between the molecules are affected
by the Lorentz transformation the same way as electrostatic forces. Here Lorentz generalized
his earlier length-contraction thesis, proposing that the electrons themselves contracted, not
just the forces between them, leading him to admit that the motion of the Earth relative to
the ether should be “almost” untraceable. Some critics were quick to reject this paper, Max
Abraham charging that Lorentz’s contracted electron would be unstable unless nonelectromagnetic
forces were added to stabilize it, a possibility Abraham considered
questionable. Halfway into 1905, however, Poincaré introduced one such component, a nonelectromagnetic
pressure that explained length-contraction and stabilized electrons
(“Poincaré’s stresses”).
Poincaré, however, distrusted “intuitions” about temporal features. As he put it in The
Measure of Time, published in 1898: “We do not have a direct intuition for simultaneity, just
as little as for the equality of two periods. If we believe to have this intuition, it is an illusion.
We helped ourselves with certain rules, which we usually use without giving us account over
it” he wrote. According to Poincaré, “We choose these rules therefore, not because they are
true, but because they are the most convenient, and we could summarize them while saying:
‘The simultaneity of two events, or the order of their succession, the equality of two
durations, are to be so defined that the enunciation of the natural laws may be as simple as
possible’. In other words, all these rules, all these definitions are only the fruit of an
unconscious opportunism” (Poincaré, 1898, p. 234).
Lorentz concurred with Poincaré and the principle of relativity, but only superficially.
Again, much of Lorentz’s theory found a place in Einstein’s theory, but the metaphysical and
epistemological underpinnings of the two theories are decidedly different. Einstein
appreciated the epistemic importance of strongly linking the acceptance and rejection of
hypotheses to their impact on experiment and observation. Unlike Einstein, Lorentz had had
no problem postulating the existence of an undetectable posit.
As the quest for a better theory of light and electromagnetism moved on, analytical results and
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