20 euro - Secrets of Snow - Austria - 2023 - Silver PROOF

20 euro silver coin dedicated to the secret of Snow, PROOF.
German astronomer and mathematician Johannes Kepler (1571–1630) pondered this with childlike curiosity when snow began to fall as he was walking across the Charles Bridge in Prague in 1610. This experience prompted him to write the first scientific treatise on snow crystals, Strena Seu De Nive Sexangula, in which he asks why when snowflakes fall, although each one is different from the next, they are always hexagonal in shape. A simple enough question, but one that no one had ever asked before and one that was not answered for another three hundred years. Nonetheless, in trying to answer it, Kepler provided some fascinating insights into snowflakes and asked some pertinent questions about physics, mathematics and biology.