Early modern astrologers blamed the devastating bubonic plague on a nasty alignment of Mars and Jupiter

A closer look

When you have absolutely no idea what bacteria is, you blame the sky. During the Black Death, the faculty of the University of Paris officially declared that the plague was caused by a dangerous conjunction of Saturn, Jupiter, and Mars in the sign of Aquarius. It was the ultimate 'the stars are out to get us' excuse, allowing people to completely ignore the literal millions of infected fleas jumping off rats onto their ankles.