13.7 billion years ago The Big Bang
An unimaginably large explosion from an unimaginably small particle - according to modern theory the first moment of the universe

2781 BC Egyptians invent calendar
Sirius rises in this year on the first day of the first Egyptian month - a rare event which possibly launches the Egyptian calendar system

1750 BC Planets identified in Babylon
Babylonian astronomers name many of the constellations and identify the planets

1100 BC Phoenicians use pole star
Phoenician sailors use the pole star for navigational purposes

585 BC Greek predicts solar eclipse
Thales of Miletus, traditionally the first philosopher, is credited with the prediction of a solar eclipse

550 BC Greeks develop Babylonian zodiac
The Greeks develop the Babylonian theme of the zodiac, naming it the zodiakos kyklos or circle of animals

450 BC Earth in orbit say Pythagoreans
The followers of Pythagoras maintain that the earth revolves on its own axis and moves in an orbit

350 BC Eudoxus imagines heavenly spheres
Eudoxus of Cnidus proposes the concept of transparent spheres supporting the bodies visible in the heavens

270 BC Aristarchus says earth orbits sun
On the small Greek island of Samos an astronomer, Aristarchus, comes to the startling conclusion that the earth is in orbit round the sun

140 BC Hipparchus and the astrolabe
The Greek astronomer Hipparchus is credited with the invention of the astrolabe, measuring the angle of sun or star above the horizon

130 BC Hipparchus observes precession
The Greek astronomer Hipparchus, mapping the stars, observes but cannot explain the precession of the equinoxes

129 BC Hipparchus completes star catalogue
Hipparchus completes the first scientific star catalogue, mapping some 850 stars

50 BC Maya have 52-year calendar
The Maya introduce a calendar which has a cycle of fifty-two years, known as the Calendar Round

45 BC Caesar introduces new calendar
Julius Caesar's new calendar is introduced, at a time when its predecessor has become out of step with the seasons by three months

921 Jewish calendar fixed
The Jewish calendar, deriving originally from the example of Babylon, is given its lasting form

1054 Eastern astronomers spot supernova
Astronomers in China and Japan observe the explosion of the supernova which is still visible as the Crab Nebula

1066 Marvellous comet appears
Halley's comet, appearing in the Normans' annus mirabilis, is later depicted in the Bayeux tapestry

1543 Copernicus goes heliocentric
Polish astronomer Nicolaus Copernicus publishes a book suggesting that the earth moves round the sun

1576 Brahe creates Uraniborg
Danish astronomer Tycho Brahe builds Uraniborg, on the island of Hven, and makes it the world's leading observatory

1582 Accurate calendar for Catholics only
The new and more accurate Gregorian calendar is introduced by Gregory XIII in the papal states

1596 Brahe and Kepler in Prague
Tycho Brahe enters the service of the emperor Rudolf II in Prague, where he invites Johannes Kepler to join him

1609 Planets move elliptically
Johannes Kepler, in Prague, puts forward the radical proposition that the planets move in elliptical rather than circular orbits

1610 Galileo aims telescope at sky
Galileo, with his new powerful telescope, observes the moons of Jupiter and spots moving on the surface of the sun

1613 Galileo proves Copernicus right
Galileo publishes his evidence, from sun spots, proving Copernicus right and Ptolemy wrong on the solar system

1632 Galileo threatened with torture
The Inquisition convicts Galileo of heresy and he denies the truth of Copernicus - on being shown the instruments of torture

1655 Huygens discovers rings of Saturn
Christiaan Huygens, using a home-made telescope, describes accurately the rings of Saturn and discovers the planet's largest moon, Titan

1672 Distance to sun calculated
Giovanni Domenico Cassini, working in the Paris royal observatory, calculates the distance from the earth to the sun and is only 7% out

1680 Comet intrigues Halley
A comet intrigues Edmund Halley, who works out that it has been around before

1758 Comet proves Halley right
A comet returns exactly at the time predicted by English astronomer Edmond Halley, and is subsequently known by his name

1769 Cook observes transit of Venus
Captain Cook observes in Tahiti the transit of Venus, the primary purpose of his voyage to the Pacific

1781 Herschel sees Uranus
William Herschel discovers Uranus, the first planet to be found by means of a telescope, and names it the Georgian star

1796 Nebular hypothesis by Laplace
French astronomer Pierre-Simon Laplace publishes his nebular hypothesis, arguing that the planets formed from a mass of incandescent gas

1894 Lowell builds observatory on Mars Hill
Wealthy US astronomer Percival Lowell builds an observatory at Mars Hill in Flagstaff, Arizona

1915 Nearest star to earth discovered
The nearest star to earth, the red dwarf Proxima Centauri 4.22 light years away, is discovered by Robert Innes, Scottish director of the Johannesburg Observatory

1924 Ours is not the only galaxy
US astronomer Edwin Hubble proves that the nebula Andromeda is vastly further away than other stars and can only be a separate galaxy

1926 Our galaxy rotates
To explain the irregular movement of stars, Swedish astronomer Bertil Lindblad proposes the theory that our galaxy rotates

1926 Eddington analyzes the stars
British astrophysicist Arthur Eddington compares mass and luminosity in The Internal Constitution of the Stars

1929 The universe is expanding
US astronomer Edwin Hubble uses the red shift of light from galaxies to demonstrate that they are receding from each other and the universe is expanding

1948 'Steady-state' theory
British astronomer Fred Hoyle puts forward a 'steady-state' theory of the universe, in which matter is continually created

1948 Massive telescope on Mount Palomar
A 200-inch telescope goes into service at the Mount Palomar Observatory in California

1957 Stellar nucleosynthesis explained
Fred Hoyle, William Fowler, and Margaret and Geoffrey Burbidge explain stellar nucleosynthesis

1957 First artificial satellite
The USSR launches Sputnik, the world's first artificial satellite

1957 Sputnik inspires NASA
The success of the USSR in launching Sputnik prompts the establishment of NASA in the USA

1957 Laika orbits the earth
The Russian spacecraft Sputnik II puts into space a living creature, the dog Laika

1959 Luna 1 orbits the sun
Soviet spacecraft Luna 1 goes into orbit round the sun, between the orbits of Earth and Mars

1959 Luna 2 strikes the moon
Soviet spacecraft Luna 2 successfully strikes the moon, in the Palus Putredinus region

1959 Luna 3 photographs far side of the moon
Soviet spacecraft Luna 3, passing by the moon at a distance of some 40,000 miles, is able to photograph the far side

1961 Gagarin is first in space
Soviet cosmonaut Yuri Gagarin becomes the first human to travel in space, orbiting the earth once in Vostok 1

1961 Shepard is first American in space
US astronaut Alan Shepard becomes the first American in space, with a suborbital flight in Freedom 7

1961 US to put man on moon
President Kennedy commits the US to placing a man on the moon and bringing him back safely by 1970

1963 Tereshkova is first woman in space
Soviet cosmonaut Valentina Tereshkova becomes the first woman in space, flying solo in Vostok 6

1965 Leonov is first to walk in space
Soviet cosmonaut Aleksei Leonov is the first to walk in space, moving round outside the Voshkod 2 spacecraft for more than ten minutes

1966 Luna 9 lands on the moon
The Soviet spacecraft Luna 9 is the first to achieve a soft-landing on the moon and to send back photographic data from the surface

1966 Luna 10 orbits the moon
The Soviet spacecraft Luna 10 orbits the moon and broadcasts the Internationale to the 23rd Congress of the Communist Party

1967 First known pulsar
British research student Jocelyn Bell and her Cambridge supervisor Antony Hewish identify the first known pulsar

1968 Astronauts orbit the moon
Three US astronauts become the first humans to leave the earth's orbit, reaching the moon and going into its orbit in Apollo 8

1968 First sight of earthrise
The US astronauts in Apollo 8 are the first humans to see (and photograph) the sight of the earth rising above the moon's horizon

1969 Giant leap for mankind
Neil Armstrong, commander of the US space mission Apollo 11, sets foot on the moon and says: 'That's one small step for man, one giant leap for mankind.'

1971 First space station
The Soviets put into orbit the first space station, Salyut 1, but the crew of three die on returning to earth

1971 Driving on the moon
In the Apollo 15 mission US astronauts David Scott and James Irwin drive the vehicle Rover-1 on the surface of the moon

1975 US and Soviet astronauts rendezvous in space
Astronauts Tom Stafford and Aleksei Leonov shake hands when their Apollo and Soyuz craft successfully dock in space

1976 Space probe lands on Mars
The landing section of the US spacecraft Viking 1 detaches from the orbiter and makes a successful landing on Mars

1976 Viking 2 on Mars
333 days after leaving Earth, the landing section of the US spacecraft Viking 2 touches down on Mars and begins sending back photographs

1986 Space shuttle explodes
The US Space shuttle Challenger explodes with seven on board less than two minutes after lift-off

1986 Core of Mir launched
The Soviets launch the first module (the living quarters) of their Mir Space Station

1989 Galileo launched
The US unmanned spacecraft Galileo is launched from a space shuttle on a six-year voyage to Jupiter

1990 Hubble Space Telescope
The Hubble Space Telescope is launched from a space shuttle and goes into orbit 370 miles (600 km) above the earth

1991 Galileo snaps asteroids
The US spacecraft Galileo provides scientists with close-up photographs of two asteroids, Gaspra and Ida

1995 Galileo enters Jupiter's atmosphere
An atmospheric probe, released from the US spacecraft Galileo, enters the atmosphere of the planet Jupiter

1997 Vehicle on surface of Mars
Sojourner, a robot roving vehicle, detaches from Mars Pathfinder to analyse the surface of the planet

1998 International Space Station
The first module is launched of the International Space Station, a cooperative venture by five space agencies (USA, Russia, Japan, Canada, Europe)

2003 Space shuttle disaster
The US space shuttle Columbia disintegrates, with seven on board, when re-entering the earth's atmosphere

2006 Pluto demoted
The International Astronomical Union demotes Pluto to the new category of 'dwarf planet'

2014 November 12 Spacecraft lands on comet
The uncrewed Rosetta spacecraft's Philae probe successfully lands on Comet 67P, the first time in history that a spacecraft has landed on such an object.

2015 March 6 NASA probe visits dwarf planet
NASA's Dawn probe enters orbit around Ceres, becoming the first spacecraft to visit a dwarf planet

2015 July 14 Pluto visited for the first time
NASA's New Horizons spacecraft performs a close flyby of Pluto, becoming the first spacecraft in history to visit the distant world.

2015 September 14 Gravitational waves detected
Gravitational waves are detected for the first time, by LIGO

2015 September 28 Water found on Mars
NASA announces that liquid water has been found on Mars

2015 December 22 First reusable rocket
SpaceX lands an unmanned Falcon 9 rocket, the first reusable rocket to successfully enter orbital space and return

2016 August 24 Closest planet outside solar system discovered
Proxima Centauri B is discovered as the closest exoplanet to Earth

2018 July 25 Lake found under ice cap on Mars
Scientists report the presence of a subglacial lake on Mars, 1.5 km (0.93 mi) below the southern polar ice cap and extending sideways about 20 km (12 mi), the first known body of water on any planet apart from our own

2019 April 10 First image of a black hole
Scientists from the Event Horizon Telescope project announce the first ever image of a black hole, located in the centre of the M87 galaxy

2019 October 18 First all-female spacewalk
NASA astronauts Jessica Meir and Christina Koch conduct the first all-female spacewalk outside the International Space Station