Michelson-Morley Experiment

Maxwell's equations of electromagnetism yield solutions for travelling electromagnetic waves. The speed of light comes naturally out of these solutions. A natural question to ask was what reference frame that this speed is to be measured in. The Michelson-Morley experiment was a precision measurement which showed that the speed was independent of the relative motion of the observer. This then suggested that the speed of light is independent of the observer, and formed one of the postulates of the special theory of relativity. For a detailed explanation of the Michelson-Morley experiment see Claustrophobic Physics Michelson-Morley experiment.

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t say so what is the big deal - it's just something to calculate the dot product of two vectors. The subtle difference is that in curved spacetime the "angle" between vectors depends on where you are in spacetime, and therefore g is a machine which operates differently at different spacetime points. Viewed backwards, if you know how to calculate the dot products of vectors everywhere, you must understand the curvature of the space (and therefore the g machine specifies the geometry). For this reason, the metric tensor enters into virtually every operation in general relativity (and some in special relativity).

There are a variety of techniques for d