10: Alchemy

The idea of morphing lead into gold may seem a little crazy these days, but take a step back and pretend you live in ancient or medieval times.

Pretend you never took high-school chemistry and know nothing about elements or atomic numbers or the periodic table. What you do know is that you've seen chemical reactions that seemed pretty impressive: substances change colors, spark, explode, evaporate, grow, shrink, make strange smells - all before your eyes.

Now, if chemistry can do all that, it seems pretty reasonable that it might be able to turn a dull, drab, gray metal into a bright, shiny yellow one, right? In the hopes of getting that job done, alchemists sought out the mythical "philosopher's stone," a substance that they believed would amplify their alchemical powers.

They also spent a lot of time looking for the "elixir of life." Never found that, either.

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