= Postulates of special relativity
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The first postulate is <Einstein's principle of relativity>: nongravitational laws have the same form in every <inertial frame>. The second states that light in vacuum propagates at the same finite <speed of light> $c$ in every <inertial frame>, independently of the source's motion. Together with the usual spacetime symmetries and calibrated coordinates, these postulates yield the <Lorentz transformation>. The relativity principle alone also admits the <Galilean transformation> with its infinite invariant-speed limit.
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