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Then, Albert Einstein came along.
In 1905 and 1915, Einstein proposed his special and general theories of relativity, respectively. These theories validated all those long-running suspicions about the very concept of time and change.
Relativity rejects Newton’s notion about time as a universal physical phenomenon.
By Einstein’s era, researchers had shown that the speed of light is a constant, regardless of the velocity of the source.
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To take this fact seriously, he argued, is to take all object velocities to be relative.
Nothing is ever really at rest or really in motion; it all depends on your “frame of reference.” A frame of reference determines the spatial and temporal coordinates a given observer will assign to objects and events, on the assumption that he or she is at rest relative to everything else.
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