The best analogy I've heard to the speed of light is the horizon. No matter which direction you move in or what speed all around you the horizon remains at a constant distance and the speed of light remains constant as well. It seems to contradict logic, but only if you assume the earth is flat and the passage of time is absolute.<br />
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In college Einstein had this realization while looking at two widely separated clock towers. It occurred to him the only thing that could explain the speed of light being the same was if time travel was involved. The assumption was as he moved towards one clock tower he moved through time slower so the light coming towards him from the tower appeared to be moving at the same speed. Away from a tower, and the opposite occurred. Time is therefore relative to the motion of the observer to whatever they are moving towards or away from and there is no fixed time or absolute time.<br />
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Later Einstein expanded on this idea to create the Strong Equivalency Principle of motion. It shows that time is just another physical property no different from size, shape, or color and that all of these properties are interchangeable. As you move towards something at close to the speed of light you literally grow shorter from front to back, wider from side to side, and bluer in color. Away and the opposite occurs with the individual turning red instead of blue. <br />
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They are trading one physical property for another, space-time for mass-energy because they are all so intimately related they form a continuum or something whose parts cannot be separated. Space without time or matter or energy is a contradiction because each defines the other. Space and time are not ethereal backdrops we cannot manipulate, but part of what defines everything including ourselves.

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One day Einstein was on the train. A lady asked him: excuse me, does Princeton stop at this train?

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