Albert Einstein’s legendary reputation as history’s greatest theoretical physicist, which National Geographic seeks to mine for humanity in Genius, is due in large part to his theory of relativity — actually two related theories — which continues to form a central pillar of modern physics a century after their development.
Einstein’s theory of special relativity, which he developed in 1905, describes how the laws of physics are the same for all observers who aren’t accelerating. In a vacuum, the motion of observers doesn’t influence the speed of light. Taken all together, this means that events could appear to take place at different points in time, depending on the position of the observer. For example, some stars that appear to shine brightly in our night sky actually burned out millennia ago, but because of our position in space, we have not yet observed those events. Special relativity therefore unified space and time into a single concept: space-time.
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