1) The Cuban Missile Crisis in 1962 brought the United States and the Soviet Union to the brink of nuclear war during the Cold War.

2) The largest living structure on Earth is the Great Barrier Reef, spanning over 2,300 kilometers (1,400 miles) along the coast of Australia.

3) The fastest recorded serve in tennis was achieved by Sam Groth at 163.7 miles per hour (263.4 kilometers per hour) during a tournament in 2012.

4) In Norse mythology, the Valkyries are divine maidens who serve Odin, the chief god. They are responsible for selecting warriors worthy of entering Valhalla and escorting them to the afterlife. They are often depicted as powerful and beautiful figures, riding winged horses and wielding spears.