Why Is a Week Seven Days Long?
The week is the only unit of time with no basis in astronomy. Days, months and years track real motions. Seven days tracks seven visible moving objects in the sky, and a Babylonian habit that never stopped.
astronomy
Why Is Nuclear Fusion Always 30 Years Away?
The joke is old and the reason is specific: fusion needs conditions that only exist inside stars, and building them on Earth costs more energy than the reaction has so far returned.
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