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3000 BCE
Stone Hinge
The main stones of Stonehenge are put into place. -
2000 BCE
Calendar
First solar-lunar calendars -
280 BCE
Earth-sun
Aristarchus suggests the Earth revolves around the Sun. He provides first estimation of Earth-Sun distance. -
240 BCE
Circumference
Eratosthenes measures the circumference of the earth with surprising accuracy -
130 BCE
Star Map
Hipparchus develops the first accurate star map and star catalog with over 850 of the brightest stars. -
45 BCE
Julian Calendar
Introduction of the Julian calendar, a purely solar calendar, to the Roman Empire. -
140
Geocentric
Ptolemy suggests geocentric theory of the universe in famous work Mathematike Syntaxis -
813
School of Astronomy
Al Mamon founds the Baghdad school of astronomy. -
1054
Supernova
Chinese astronomers observe supernova in Taurus. -
1120
Cairo Observatory
Construction of an observatory in Cairo was begun in 1120 A.D. This is possibly the first observatory built in Medieval Islam. Unfortunately, the patron of the observatory was found guilty of several crimes including communication with Saturn, and was sentenced to death. The observatory was then destroyed in 1125 A.D. and the personnel were forced to flee for their lives. -
1259
First Observatory
An observatory was built for the famous Persian astronomer, Nasir al-Din al-Tusi. The patron of the observatory was Mongol ruler, Hulagu, who was addicted to astrology. The observatory, built upon a flattened hill, was named Maragha observatory. The observatory included an extensive library and many instruments set up in the open air. -
1420
Central Asia Observatory
Ulugh Beg (1394-1449), noted astronomer, had an observatory built at Samarkand in central Asia. The observatory was a 3-story building, but also contained instruments that were outdoors. Ulugh Beg's observatory produced astronomical tables that included a catalogue of over 1,000 stars. His observatory had enjoyed three decades of existence. And he is remembered as perhaps the most important observational astronomer of the 15th century. -
1543
Heliocentric
Copernicus publishes his heliocentric theory of the Universe. -
1572
Tycho Brahe
Tycho Brahe discovers a supernova in constellation of Cassiopeia -
1582
Gregorian Calender
Pope Gregory XIII introduces the Gregorian calendar. -
Bayer designation
Johann Bayer introduces Bayer designation of stars, assigning Greek letters to stars, still in use today. -
Telescope
Hans Lippershey, a Dutch spectacles maker invents the telescope. -
Galileo
Galileo uses telescope for astronomical purposes. He discovers 4 Jovian moons, the Moon's craters and the Milky Way galaxy. -
Kepler's Laws
Kepler's First and Second Laws of Planetary Motions are announced. -
Kepler's third law
The Third Law of Planetary Motion is announced by Kepler in his work Harmonice Mundi (Harmony of the World). -
Saturn
Christian Huygens discovers Saturn's rings and Titan, the fourth satellite of Saturn -
Mars Markings
Huygens notes markings on Mars. -
Martian Ice caps
Martian polar ice caps are noted by Cassini. -
Reflecting Telescope
The first reflecting telescope was built by Newton. -
Variable star
Geminiano Montanari discovers the star Algol is not steady in brightness, thus recognizing the first variable star. -
Speed of Light
While in Paris, Danish astronomer Ole Romer measures the speed of light. -
Ring Split
Cassini discovers that Saturn's rings are split into two parts, so that today the gap is called the "Cassini Division". -
Universal Gravitation
Newton publishes his theory of universal gravitation in the work Philosophiae Naturalis Principia Mathematica. This is seen to be the start of Modern Astronomy. -
Halley's comet
Halley correctly predicts the return of a comet (Halley's comet) in 1758. -
Johann Palitzsch
Johann Palitzsch observes Halley's comet as predicted by Halley in 1705. -
Uranus
The discovery of Uranus by Herschel -
Messier objects
Messier discovers galaxies, nebula and star clusters while looking for comets. He compiles a catalogue of these objects (Messier objects). -
Asteroid
Piazzi discovers first asteroid, Ceres. -
Sunspots
Samuel Heinrich Schwabe describes the sunspot cycle. -
Neptune
Johann Galle observes and discovers Neptune. His observations were prompted by mathematical calculations by French astronomer Joseph Leverrier and English astronomer John Couch Adams. -
Rockets
Rocket pioneer Konstantin Tsiolkovskii was born. Tsiolkovskii's work in early rocketry earned him the title of "Father of Astronautics". Many of his proposals concerning rocketry were later put into use including: use of liquid hydrogen and liquid oxygen as rocket fuel and multi-stage rocket design for achieving Earth orbit or interplanetary flight. -
Period: to
spectral analysis
The beginning of spectral analysis of stars by Sir William Huggins -
solar prominences
Jansen and Lockyer observe solar prominences. -
Stellar Spectrum Photographs
Henry Draper takes a photograph of the stellar spectrum of Vega. This is the first of its kind. -
Mars' Moons
Asaph Hall discovers Phobos and Deimos, the moons of Mars. -
Mars' canals
Schiaparelli observes the canals on Mars. -
Great red Spot
The Great Red Spot on Jupiter becomes prominent. -
Sun Study
Mount Wilson Observatory was established for study of the Sun. -
Theory of Relativity
Albert Einstein introduces special Theory of Relativity in paper Electrodynamics of Moving Bodies. -
Hertzsprung
Hertzsprung describes giant and dwarf stars. -
Cepheid variables
Henrietta Swan Leavitt discovers Cepheid variables. -
rocketry
Robert Goddard begins practical rocketry. -
General Relativity
Albert Einstein introduces his general Theory of Relativity. -
Galaxies
Hubble shows that galaxies exist outside the Milky Way galaxy. -
Center of the Galaxy
Oort shows the center of the Milky Way galaxy is in Sagittarius