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"Relativity"
is a concept rooted in the tension between appearance
and reality, and it reaches far back in history. Heraclitus
argued that only change is real; Parmenides argued that
change is impossible, and his follower Zeno invented
paradoxes illustrating many of the problems in concepts like
space, time, and infinity. Protagoras even argued that
there is no single, correct view of reality, but that reality
for any person is precisely as in seems to that person. In his
words, "Man is the measure of all things".
Plato
used mathematical reasoning to discern reality from mere appearance,
and modern natural science emerged from centuries of effort
to acquire objective knowledge. The greatest scientists of the
Renaissance and Enlightenment - including Copernicus,
Kepler, Galileo, and Newton
- believed that some "real" or "absolute" space and time are
independent of the senses. But Immanuel Kant, J.C.
Maxwell, Ernest March, and Henri Poincare chipped
away at this idea in the 18 and 19th centuries.
In
1905, Albert Einstein published his Special Theory
of Relativity, followed by the General Theory of
Relativity in 1916. He firmly established (1) the idea that
all judgement about motion is a matter of perspective;
(2) that energy and mass are interrelated (E=mc2); and (3) that
nothing can move faster than the speed of light (which does
not vary). Einstein's theory of the space - time continuum
was dramatically confirmed in a 1919 experiment during a solar
eclipse.
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