When I was learning multiplication, my father showed me the “rule of 9.” Multiply any number by 9, he said, and then add together the digits of the product, and you will always land on 9. 9 × 2 = 18 → ...
A century ago, the strange behavior of atoms and elementary particles led physicists to formulate a new theory of nature. That theory, quantum mechanics, found immediate success, proving its worth ...
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