In 1961, scientist Frank Drake wrote down a simple-looking equation for estimating the number of active, technologically-advanced, communicating civilizations in the Milky Way. From first principles, there was no good way to simply estimate a number, but Drake had the brilliant idea of writing down a large number of parameters that could be estimated, which you would then multiply together. If your numbers were accurate, you'd arrive at an accurate figure for the number of technologically advanced civilizations that humanity could communicate with, within our own galaxy, at any given moment. It's a brilliant idea in concept, but one that's become less and less useful as we've learned more about our Universe. As it stands today, the Drake equation is broken, but we know enough about the Universe to construct an even better framework.

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