27 August

1962: On 27 August 1962, the NASA Mariner 2 spacecraft was launched sending it on a three-and-a-half month flight to Venus. The first spacecraft to fly by another planet, Mariner 2 was built as a backup to Mariner 1, which failed shortly after launch.

It returned information confirming that Venus is a very hot world with a cloud-covered atmosphere composed primarily of carbon dioxide.

413 BC: On 27 August 413 BC, a lunar eclipse caused panic on Athens fleet and thus affected the outcome of a battle in the Peloponnesian War. The Athenians were ready to move their forces from Syracuse when the Moon was eclipsed. The soldiers and sailors were frightened by this celestial omen and were reluctant to leave. Their commander, Nicias, consulted the soothsayers and postponed the departure for 27 days. This delay gave an advantage to their enemies, the Syracusans, who then defeated the entire Athenian fleet and army, and killed Nicias.