The Gregorian Calendar Takes Effect
On October 4, 1582, the last Julian calendar day ended in Catholic Europe; the next was October 15.
Britain Adopts the Gregorian Calendar and Skips Eleven Days
On September 2, 1752, Britain skipped eleven days to adopt the Gregorian calendar, and September 3 to 13 of that year never happened.
Neptune Is Found Where the Mathematics Said It Would Be
On September 23, 1846, Neptune was observed at Berlin within a degree of the position predicted by Le Verrier's mathematics.
The First Photograph of Earth from Space
A V-2 rocket carried a camera to 105 kilometres on 24 October 1946 and took the first photograph of the Earth from space.
Luna 3 Photographs the Far Side of the Moon
Luna 3 photographed the far side of the Moon on October 7, 1959, and sent back the first images of a hemisphere never seen from Earth.
Viking 2 Lands on Mars at Utopia Planitia
On September 3, 1976, Viking 2 landed on Mars at Utopia Planitia and ran the first experiments designed to detect life there.
NASA Launches Voyager 1 Toward the Outer Planets
On September 5, 1977, NASA launched Voyager 1, which later became the first human-made object to reach interstellar space.
The Galileo Spacecraft Is Launched to Jupiter
On October 18, 1989, the Galileo spacecraft was launched aboard the shuttle Atlantis on a six year journey to Jupiter.
51 Pegasi b, the First Planet Found Orbiting a Sun-Like Star
On October 6, 1995, the first planet found orbiting a sun-like star was announced: 51 Pegasi b, a hot Jupiter.
Mars Global Surveyor Reaches Mars Orbit
On September 11, 1997, Mars Global Surveyor entered orbit around Mars and went on to map the whole planet for nine years.
NASA Loses Contact with the Mars Climate Orbiter
On September 23, 1999, NASA lost the Mars Climate Orbiter because of a mismatch between imperial and metric units.
India Launches Its First Moon Mission
On October 22, 2008, India launched Chandrayaan-1, its first lunar mission, which found evidence of water on the Moon.
LIGO Detects Gravitational Waves for the First Time
On September 14, 2015, LIGO detected gravitational waves from merging black holes, confirming a prediction Einstein made in 1916.