## Space is uniform

Einstein developed his ideas about the basic nature of space and time whilst working in the patent office in Zurich. It became obvious to him that if the ether does not exist, then we have 'empty space'. In empty space nothing can distinguish one place from another and we have to abandon the possibility of 'marking' a point in space to distinguish it from any other point. Einstein's next logical step was to apply the principle of symmetry, stating that any place in empty space devoid of all matter is indistinguishable from any other. There are no milestones in empty space! There is no, meaning in going from 'here' to 'there', because there is no difference between here and 'there'! A dictionary definition of motion is 'change of position or place'. There are no places in empty space, and therefore no such thing as absolute motion or absolute velocity.

We can of course talk about distances between material objects, like the earth and the moon. Speed of travel relative to such objects makes sense, but it does not make sense to talk about an 'absolute speed' relative to empty space. One cannot define an absolute stationary set of coordinates, or an absolute velocity relative to such coordinates. Einstein 'wiped the slate clean' and, starting with the assumption of complete symmetry, set out to build a chain of logic leading to conclusions which could be tested.

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