July 21

356 BC – The "Temple of Artemis" in Ephesus, one of the Seven Wonders of the World, is destroyed by arson.

1620 – Jean Picard, French astronomer, cartographer and hydraulic engineer, is born.
Regarded as the founder of modern astronomy in France, his most important work is thought to be the first measurement of the circumference of the Earth.

1914 – Sinope, the outermost known moon of Jupiter, is discovered by Seth Barnes Nicholson at Lick Observatory.

1969 – At 02:56 UTC, astronaut Neil Armstrong becomes the first person to walk on the Moon, followed 19 minutes later by Edwin "Buzz" Aldrin.
Apollo 11 spends 21 1/2 hours on the surface, leaving behind a plaque that reads, "Here men from the planet Earth first set foot upon the moon, July 1969 A.D. We came in peace for all mankind."