Scientists believe that the event leading to the extinction may have been a massive asteroid impact or huge volcanic activity. Events such as these could have blocked out sunlight and significantly changed the Earth's ecology.

It wasn't until the 16th century that most mathematical symbols were invented. Before this time math equations were written in words, making it very time consuming.

Each of the suits on a deck of cards represents the four major pillars of the economy in the middle ages: heart represented the Church, spades represented the military, clubs represented agriculture, and diamonds represented the merchant class.

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