An Astronomical Timeline

Compiled by Brian Timmins

Page One of Five

Page 1	Pre-Recorded History to 1682
Page 2	1683 - Newton's "Principia" to 16th July, 1968
Page 3	20th July, 1969 - Armstrong & Aldrin on the Moon to the end of the 20th century
Page 4	1st January 2001 to the 31st December 2007
Page 5	1st January 2008... Onwards and Upwards...

The first two actual year points of division of these pages are not arbitrary. The whole thing was getting too cumbersome to be on one page and so now multiple pages. The 1682-1683 division was based on the conventional wisdom that the publication of "Principia" by Isaac Newton, ushered in the era of modern Astronomy. The 1968-1969 division was, of course, based on when man first set his foot on a body other than earth. All subsequent divisions are purely for size reasons (keeping pages under 100K) - there is so much more information becoming available.

Note: All dates in the pre-recorded history, and pre-christian sections are suspect. Some, such as the birth date of Supernova 1987a can be considered fairly accurate but others can be out by a long way.
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Goto Recorded History - Pre Christian Era Goto Recorded History - Early Post Christian Era Goto The Fourteenth & Fifteenth Centuries Goto The Sixteenth Century Goto The Seventeenth Century up to 1682

Pre-Recorded History

13,700,000,000 BC

Latest, most accurate calculation on when the Universe was formed.

12,000,000,000 BC

Latest estimate of when the Milky Way galaxy was formed. For those of you not aware, calculations show that our Galaxy is not a pure spiral but has two central arms of about 25,000 light years in length.

4.6,000,000,000 BC

Our solar system formed.

208,000,000 BC

The image to the right is an astrobleme (the visible remains of an asteroid impact) in what is now Quebec, Canada, created a crater 70km in diameter around 1.8 million years ago. The Manicouagan astrobleme is the second largest known visible terrestrial impact crater and is thought to be one of five more or less simultaneous strikes ranging from the Ukraine, through France into Canada, Quebec and Saint Martin, Canada and Red Wing, North Dakota, USA.
The largest known astrobleme is in South Africa and is known as the Vredefort Dome. It is over 2 million years old and is thought to have been caused by an asteroid about 10 kilometres in diameter. There is little left to be actually seen, just a segment of the ring to the north-east of Vredefort.

65,000,000 BC

An impact at Yucatan Peninsula, Mexico, created crater almost 200km across, caused global devastation and possible extinction of dinosaurs, along with an estimated 85% of all life on our planet.

168,000 BC

Supernova 1987A in the Large Magellanic Cloud explodes, seen on Earth on February 23, 1987.
(Image: Composite of RGB + UV)

48,000 BC

Astrobleme in Arizona where an iron meteor struck the planet creating a crater 4,000 feet wide and 570 feet deep. This huge lump of iron-nickel, weighing several hundred thousand tons, struck the rocky plain with an explosive force greater than twenty million tons of TNT.

30,000 BC

Earliest indications of human records of astronomical events. Bone carvings are used keep track of phases of Moon. Early people engraved patterns of lines on animal bones to keep track of the phases of the Moon.

15,000 BC

Drawings in the cave of Lascaux claimed to be of constellations (the little irregular rows of dots). However, given the lack of corroborating evidence this would seem unlikely.

7000 BC

Drawing of an image in the "Chanchal Mahoma" caves, Spain. It would take a brave person to argue that this is not a representation of the phases of the Moon.

Recorded History - Pre Christian Era

4800 BC

A calendar stone was found near the border between Egypt and Sudan dating from this time.

4500 BC

Stone structures in Carnac, France. In 1887, H. de Cleuziou argued for a connection between the rows of stones and the directions of sunsets at the solstices. In more recent times, studies by Alexander Thom and his son Archie, in the years 1970 to 1974, documented a detailed survey of the Carnac alignments, and they wrote a series of papers on the astronomical alignments of the stones as well as a statistical analysis supporting his concept of the megalithic yard (An almost apocryphal measurement said to be used in megalithic times).

4004 BC

Calendars developed in Mesopotamia. The image on the right shows venus (8-pointed star) and seven stars (balls) possibly the Pleiades.

Mesopotamian ziggurats serve as observatories. Mesopotamian astronomers made careful observations from the tops of towers, which looked like truncated pyramids, called ziggurats.

This was the date postulated by Archbishop James Ussher that humankind was created. In his work, he calculated the date of creation to be nightfall preceding 23 October, 4004 BC. Ussher's chronology, though obviously at variance with modern scientific dating, represents a considerable feat of scholarship. It required the Bible to be firmly anchored in history, which needed a huge depth of learning in ancient history, including the rise of the Persians, Greeks and Romans; never mind a deep knowledge of many of the world's most difficult languages.

3000 BC

The Sumerians make lists of bright stars and give the first names to constellations in the zodiac. They also record the movements of the five visible planets - Beginnings of the science of astronomy.

2800 BC

The construction of Stonehenge is started. The building of Stonehenge took place over many centuries and was completed around 1000 BC. Alignments of the stones at Stonehenge mark the rising and setting points of the Sun at the solstices.

2600 BC

Religion based on observations of stars reaches its zenith in Egypt during the 3rd dynasty. Later replaced by sun worship.

2485-2375 BC

The large pyramids, at Giza in Egypt. There is great debate and contention throughout various scientific disciplines, from archaeologists through historians to astronomers, about the astronomical connection. A certain Robert G Bauval puts it thus:

1. Did the pyramid builders have a keen interest in the stars? Yes.
2. Do the pyramids have astronomical qualities in their design? Yes.
3. Is there a feature in the pyramids that links them to Orion's belt? Yes.
4. Are there contemporary or near-contemporary texts which are associated to pyramids in that region and which speak of a link with Orion? Yes.
5. Did the ancient Egyptians imagine the pyramids to be 'stars'? Yes.

From the above we must conclude that there is much that suggests a deliberate intention to represent Orion's belt at Giza.

Remembering that Mr Bauval is not an astronomer, you must make up your own mind because there is no single world-wide agreement on a single explanation for the few facts that are unarguable (1-3 above). Some of the hypotheses put forward in Mr Bauval's works are regarded by most mainstream archaeologists and historians as a form of pseudoscience. Several Egyptologists have entertained the general notion that some astronomical correlations may have figured in or been represented by certain physical features and orientations in Ancient Egyptian monuments - but not the exact claims and correlations put forward by Bauval and his co-authors. Perchance you are interested (we all like a bit of contention) there is More... at Mr Bauval's website.

2354 BC

En Hedu'anna: The chief priestess of the Moon Goddess in around 2350 BC - this was her priestly name. Her birth name is unknown but she was the daughter of Sargon of Akkad - the founder of the Sargonian Dynasty in ancient Babylon. She is the very first named astronomer about whom there is accurate recorded information. There are those amongst us who pooh-pooh calling her an astronomer, but her job was to observe and record the movements and timings of the sun, moon, planets and stars. At the end of the day this is exactly what an observational astronomer does. So, nowadays, though we quite rightly laugh at the astrological purposes for which these recordings were used, when all is said and done... an Astronomer she was!

2300 BC

Chinese sources start reporting observations. Their first recorded observation of a comet is from 2296 BC, and a solar eclipse is recorded in 2137 BC.

2000 BC

The oldest written sources from Babylon, including the oldest known recording of a lunar eclipse took place at Ur in a letter from his astronomer to the Assyrian king, Ashurbanipal.

Standing stones, which, like Stonehenge have almost certainly some sort of astronomical alignment are built in Avebury, England.

Mesopotamian and Egyptian astronomers begin to map the heavens; They create the 365-day year and know about both the quarter day innacuracy and the nineteen year cycle with the moon.

The Temple of Amen-Ra at Karnak, Egypt was built so that its main axis points to the sunset at the summer solstice.

1900 BC

A major stage of Stonehenge completed

1800 BC

Babylonians begin to keep observational records and produce a star catalogue.

1600 BC

"The Nebra Disc": The oldest known definite representation of the sky. The disc 32cm in diameter shows a golden ship, Sun, Moon and stars, including the constellation Pleiades just before the eclipse as they appear in reference to a local mountain on the horizon, the Brocken. The artifact was discovered within a pit inside a Bronze Age ringwall, near the German town of Nebra and is around 3600 years old. Astronomers have confirmed that the sky map matches the latitude of the place where it was found.

The Egyptians start to use sundials.

Chaldean astronomers identify and establish the zodiac.

1400 BC

The oldest Egyptian water clocks. The Egyptians introduce a year with 365 days, 12 months of 30 days + 5 extra birthdays for the gods Isis, Osirus, Horus, Nepthys and Set.

1350 BC

Tutankhamen invents device for charting star positions Akhenaten invents religion based on sun god Atun.

1302 BC

Chinese recording of a solar eclipse and a supernova. They begin centuries long series of observations of eclipses. Chinese astronomers recorded 900 solar and 600 lunar eclipses over a period of 2600 years.

1100 BC

Egyptian lists of stars along the ecliptic for measurement of time at night. They divided the ecliptic into 10-degree areas, decanes.

1000 BC

• Chinese astronomers begin predicting eclipses.
• Babylonians develop the concept of 360 degrees in a circle.
• Stonehenge finally completed. In the big image - the five major planets. For the rest of the 21^st century there will be only three other chances to see them so tightly grouped: September 2040, July 2060, and November 2100.

800 BC

The Chinese observe sunspots.

700 BC

Hesiod describes practical uses for astronomy. Hesiod's poem "The Works and Days" contains practical astronomical advice for navigation and for agricultural activities.

The Works and Days - ll. 609-617

But when Orion and Sirius are come into mid-heaven, and rosy-fingered Dawn sees Arcturus ³⁰, then cut off all the grape-clusters, Perses, and bring them home. Show them to the sun ten days and ten nights: then cover them over for five, and on the sixth day draw off into vessels the gifts of joyful Dionysus. But when the Pleiades and Hyades and strong Orion begin to set ³¹, then remember to plough in season: and so the completed year ³² will fitly pass beneath the earth.

30. September
31. The end of October
32. That is, the succession of stars which make up the full year

Tr. Hugh G. Evelyn-White, 1914

The Babylonians used their long record of eclipses to see regular patterns of eclipses and used these patterns to predict lunar eclipses.

650 BC

• A star chart known from Assurbanipal's library
• Archilochus of Paros, a Greek poet describes a solar eclipse

  "...Since Zeus father of Olympians
  made night from mid-day
  hiding the light of the shinning-sun
  and sore fear upon man"

600 BC

• The birth of Greek science proper. Thales assumes that it is possible to understand the Universe using simple rules, and observes that the constellation we know as "The Plough"(US: Big Dipper) never moves below the horizon in Greece, but it does when viewed from Egypt. He also predicts a solar eclipse which eventually took place during a battle between the Lydians and the Persians. They were so stunned by the eclipse they ended the battle.
• The Earth is assumed to float in a large ocean
• First astronomy texts written in India
• Pherekydes of Syros (teacher of Pythagoras) performs astronomical calculations with measurements taken with a heliotropion device in the island of Syros

580 BC

Anaximander of Miletus a student of Thales and according to some the discoverer of the gnomon, proposes that the Earth is cylindrical and isolated in space. Nothing supports it. The moon, he said, had a borrowed(reflected?) light, and received it from the sun. The sun he proposed to be not less than the earth, and the purest possible fire. He introduces the idea that stars and planets rest on crystal spheres. Anaximander's model was the forerunner of later Greek attempts to explain the heavens in non-mythological terms.

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550 BC

• Pythagoras and students develop model of solar system. The model of Pythagoras used circular paths for the celestial bodies and assumed most celestial bodies are spheres
• Diogenes of Apollonia (Diogenes Laërtius) was the first to suggest that meteorites come from space (something which was forgotten for the next 2 millenia). (A class of meteorites are named after him - Diogenites, a sub-division of Achondrites ) He made astronomical observations from Eleutherna a mountain in Crete

523 BC

Written evidence of the Zodiac from the Babylonians with 12 signs.

500 BC

Pythagoras of Samos proposes, for aesthetic reasons, that the Earth is spherical, the perfect form.

470 BC

• Anaxagoras taught that the moon shines with the reflected light of the Sun and so was able to explain the eclipses. In agreement with the mathematicians, he held that the phases of the moon, month by month, were due to its following the course of the sun by which it is illuminated, and that lunar and solar eclipses were due to the positioning of the three bodies as we understand it nowadays. He also proposed that the Sun, Moon and stars are composed of the same matter as Earth
• Oenopides measured the inclination of the Earth axis with respect to the ecliptic plane to be 24 degrees, defined the Great Year to be about 59 years, this being the length of time where the Solar timings match up with lunar timings (an interval with exact repetition of days in a year phases of the moon)
• It is thought that Pythagoras first discovered the axial tilt of the earth in respect of the zodiac

440 BC

Athens observatory on Lycabettus Hill used by Meton and Phaeinus. In his book "Enneadecaterides" Meton introduces what became known as the "Metonic" cycle. This cycle, although known earlier in Babylon and China, of 19 years, or 235 lunations, or 6,940 days is named for the Greek Meton because of the accuracy of his calculations. His calculations gave a year of ~365.263 days which was only out by about half an hour!

Leucippus of Miletus proposed that the world consisted of the void and atoms, which are imperceptible individual particles that differ only in size, shape, and position. That these particles were imperceptible meant they met Parmenides' objection to the Pythagorean's geometric points and, since they alone were unchanging, change could be explained away as merely impressions upon the human senses

430 BC

Philolaus explains the apparent daily rotation of the heavens by saying that the Earth moves around a central fire (that mankind always turns away from). A Counter-Earth moves around the fire, along with all the other heavenly bodies.

420 BC

• Lunar eclipse delays evacuation of Athenian army from Sicily. The Greeks regarded eclipses as uncertain omens. The delay doomed the Athenian army.
• Democritus of Abdera pushed the boundaries of Leucippus's atomic theory. Atoms vibrate when hitched together in solid bodies and exist in a space which is infinite in extent and in which each star is a sun and has its own world

400 BC

• Plato. Space is infinite and contains a finite universe with the Earth at the centre. All movements must be explained with circular movements. He perceived the visible world as a travesty of the world of ideas
• Eudoxus explains retrograde motion. Eudoxus's explanation involved the rotation of spheres in opposite directions. This geocentric model had the Earth at its center
• The Chinese astronomer Kan Te reports sunspots
• Democritus postulated the existence of the Milky Way galaxy

375 BC

• Ephorus of Cyme of Cyme in Aeolia, Asia Minor, a student of Isocrates, observed a splitting of a comet into two pieces
• The Homocentric Spheres of Eudoxus: Eudoxus of Cnidus invented a hugely complicated model of twenty-seven concentric spheres by which he calculated the sun's annual motions through the zodiac, the moon's motion (including its wobble), and the planets' retrograde motions
• Democritus suggests that the Milky Way is composed of many stars
• Heraclides of Pontus and Ecphantus the Pythagorean propose that the earth moves on its axis like a wheel, from west to east, about its own centre

365 BC

Chinese observations of Jupiter's moons.

360 BC

Heraclides. The Earth rotates about its own axis. Mercury and Venus orbit the Sun, which orbits the Earth. The rest of the planets orbit the Earth.

Aristotle developed a model of the solar system using 55 spheres

350 BC

The Chinese astronomer Shi Shen makes a catalogue of 800 stars.

340 BC

Aristotle argues celestial bodies are spheres. Aristotle used a number of proofs that the Earth is a sphere, including the observation that its shadow on the Moon during lunar eclipses is always a circle. He publishes an astronomical work, "De Caelo" (On the Heavens).

330 BC

• Heraclides of Pontus, agreeing with the Pythagoreans, says that the earth turns daily on its axis.He also considered each planet to be a world with an earth-like body and with an atmosphere. He also suggested that Mercury and Venus have the sun at the center of their spheres.
• Theophrastos discovers Sunspots (Independently observed, much earlier in China)
• The Chinese astronomer Wu Xian publishes a list of 1464 stars in 284 constellations.
• Autolycus of Pitane, writing what is considered to be one of the earliest pure astronomy texts comments on the geometry of spheres and defines uniform motion as being when "a point is said to be moved with equal movement when it traverses equal and similar quantities in equal times".
• Eudoxus, worked at his observatory at Cnidos where it is known he made astronomical observations. He even had his own name for what is now known as the Pelieades - the Clusterers
• Hicetas of Syracuse proposes that the apparent motion of the "fixed" stars is caused by the Earth spinning on its own axis
• Shin Shen's star catalog has almost 800 entries
• Pytheas - tides are caused by the moon.

320-250 BC

• Thirteen Towers solar observatory, Chankillo, Peru. Like Stonehenge, the observatory marked the summer and winter solstices, along with the days and weeks of the year.
• Aristarchus of Samos, in "On the Sizes and Distances of the Sun and Moon", used trigonometry to estimate the size of the Moon and its distance by the Earth's shadow during a lunar eclipse. He argues that the Sun is the centre of the solar system. But he gains no supporters. He was contradicted by philosopher's such as the stoic Cleanthes who considered Aristarchus as an atheist.
• Later Aristarchus gained support from Archimedes and others who maintained that the Moon revolved around the Earth and the Earth around the Sun which remained stationary like the stars.
• Archimedes was the first to give an upper and lower values for the solar diameter. This was probably the first indication of the "oblate spheroid" shape for astronomical bodies.
• Aristillus of Samos and Timocharis of Alexandria prepared the first true star catalog.

220 BC

Apollonius of Perga was known as 'The Great Geometer'. Though not a lot is known of his life, his works have had a very great influence on the development of mathematics. Especially his famous book "Conics" which introduced terms which are familiar to us today such as parabola, ellipse and hyperbola. He also developed a model of the solar system by using epicycles.

200 BC

• Eratosthenes of Alexandria measures the size of the Earth. H uses observations by measuring the altitude of the Sun at different locations at the same time. His estimate may have been accurate to within a few percent.
• Chang Heng begins to map China with a coordinate system. He uses the Mercator projection ("invented" in Europe in 1568) for his star chart.
• The Astrolabe devised and used by Greeks

150 BC

• Hipparchus, the greatest observer of antiquity at his Rhodes observatory, finds that Aristotle is wrong and introduces movements in epicycles (circles on circles) for the planets. He measures the distance to the Moon.
• Seleucus of Seleucia accepts Aristarchus Heliocentric model.
• Hypsicles writes On the Ascension of Stars. In this work he is the first to divide the Zodiac into 360 degrees.

130 BC

Hipparchus discovers precession, the slow change in the direction of the Earth's polar axis. He also developed a system of defining apparent brightness of stars, the basis of the current method. He publishes stellar charts and a catalogue of the positions and brightnesses of around 850 stars.

105 BC

Alexandria observatory and College of Technology was under the control of "Hero of Alexandria" (sometimes spelled Heron), who, bye-the-bye, invented the first steam engine, nearly 2 millenia before Trevethic, Stephenson, Watt et al., but did not pursue it as he considered it merely a toy!!!

80 BC

A bronze astronomical gear machine - The Antikythera Mechanism, the oldest geared mechanism known - found in a Greek shipwreck in 1901 is from this time. No-one realy knows what it was used for but one interesting fact is that some of the gearing in it represents the 19 year cycle of the sun and the moon as worked out by Meton - see 440BC.

On the left is the machine as found and on the right is a modern replica.

52 BC

Shou-chang constructs and uses an armillary ring (a very accurate sundial).

46 BC

Sosigenes of Alexandria calculates a calendar of 365.25 days which was introduced by Julius Caesar which was then used by the world until 1582 when Pope Gregory XIII introduced his "Gregorian Calendar", thus eliminating the inaccuracy of the fact that the year was actually 11.5 minutes longer. Given that the Greeks had such an effect on the history of astronomy it is a fascinating factoid that Greece was the last "western" country to adopt the Gregorian Calendar and did not do so until 1923.

Recorded History - Early Post Christian Era

100

The Chinese astronomer Zhang Heng constructs an armillary instrument that turns automatically with the heavens. It is driven by a water clock.

135-150

• Claudius Ptolemaeus (Ptolemy) published a thirteen volume series of books (the Almagest) of his studies and data concerning the stars, including the (even then) ancient records from Mesopotamia on eclipses. It put theorised that all the planets and the Sun orbit the Earth. This is called the Geocentric Theory and it was considered "deus ex machina" for around 1500 years! Even though The Almagest contained errors which were not corrected until the sixteenth and seventeenth centuries.
• The tables of the planet's positions were of such accuracy that Nicholas Copernicus computed most of his numbers from them.
• In his model the planets moved on circles (epicycles) that moved on other circles (deferents). There is a school of thought that which says that Ptolemy did not believe that his model was a "real" representation of the way things were, but was merely a "device" in order to simplify his calculations, judging the circles to be only models devised for the purpose of calculation and recognizing that the actual movements were unknowable.
• He also compiled and published a catalog with the positions of 1000 stars including a system of stellar brightnesses based partly on the earlier catalog of Hipparchus.

160

The first Science Fiction Story in history! - by Lucian of Samosata. He wrote his "True Story" parodying the weird tales told by Greeks from the Odyssey onwards. Though by training a lawyer, philosopher and lecturer many of his 80-odd books weren't at all serious. "A True Story" anticipates Jules Verne, George Lucas and, especially, Douglas Adams.

The book describes a kidnapping by extraterrestrials, star wars, and a trip to the moon! In the story Menippus meets Endymion who explains that he was kidnapped and brought to the moon while he slept. He adds that he is about to make war on the People of the Sun, whose King Phaethon has refused to allow him to colonize Venus. In the titanic struggle which follows, the People of the Sun are at last victorious and the triumphant Phaethon builds a high wall which prevents the light from his domain from reaching the moon, thus causing a total eclipse.

There was even a warning from the author at the beginning of the book:
All books are full of lies - especially serious books and most especially philosophy. My book is uniquely honest because I guarantee that it does not contain a single word of truth. There is no evidence for any of my claims. None of of the events happened to me. I did not do any research - you have been warned. Do Not Take This Seriously.

200

Cleomedes was a Greek astronomer who is known chiefly for his book "On the Circular Motions of the Celestial Bodies". This work is regarded as a book of little intrinsic value. However it has huge importance because it preserves, apparently verbatim, much of the astronomical writings of Posidonius, none of the originals of which have survived to the modern day. It is also the original source for the well-known story of how Eratosthenes measured the Earth's circumference and although some authorities consider the story apocryphal, many modern mathematicians and astronomers believe the description to be entirely possible, and consider Eratosthenes' achievement to be one of the greatest accomplishments of any of the ancient astronomers.

310 BC

The first celestial globe is cast by Qian Luozhi.

336

Chinese astronomers rediscover precession.

390

Chinese astronomers record a short-lived star, probably a supernova

420

Martianus Capella publishes a book in which he presents an astronomical system with the Earth at the centre of the Universe, the Moon, the Sun, Mars, Jupiter and Saturn in orbit around it and the planets Mercury and Venus in orbit around the Sun.

499

The Indian astronomer Aryabhata publishes a book in which the rotation of the heavens is explained by saying that the Earth rotates and there is a heliocentric solar system and the planets in elliptic orbits though there is huge debate about this. He determines the length of the year very precisely and amazingly calculates the circumference of the earth to within 0.2%.

642

The knowledge centre of Alexandria in Egypt is conquered by the Arabs shortly after the collapse of the Roman Empire. Greek astronomy survives in Islam (virtually none of the major Islamic astronomers are Arabs. Most are Persians). Europe enters the Dark Ages, although recent research has shown that they were not that dark after all.

721-725

The Chinese measure the size of the Earth.

750

The astronomy the Arabs had taken over in Egypt flourishes in Spain.

800-1000

Visby lenses possibly used to make a telescope. Visby lenses are lens-shaped manufactured artifacts made of quartz. They were found in a viking grave in Gotland dating from approximately the 10th century. The lenses may have been imported from the Middle-East via Viking trading routes, but there is also evidence of local manufacture of lenses.

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813

al-Mamun founds a school of astronomy in Baghdad and translates Ptolemy's works. Astronomical knowledge from around the world is collected and translated.

860

al-Farghani (Abu'l-Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani), born in Farghana, Transoxiana, was one of the most distinguished astronomers in the service of al-Mamun and his successors. He wrote "Elements of Astronomy" (Kitab fi al-Harakat al-Samawiya wa Jawami Ilm al-Nujum i.e. "The Book On Celestial Motion And Thorough Science Of The Stars"), which influenced European astronomy for about 400 years. He affirmed Ptolemy's theory and value of precession, but thought that it affected not only the stars but also the planets. He determined the diameter of the earth to be 6,500 miles, and found the greatest distances and also the diameters of the planets.

900

The Dunhuang star map produced. Ursa major, sagittarius and capricorn are recognizable. The three colors (white, black and yellow) indicate the schools of astronomy of Shih Shen, Kan Te, and Wu Hsien.

963

Abd-al-Rahman Al Sufi compiles his Book of the Fixed Stars and draws his star charts.

965-1039

The Arab (or Persian?) physicist, mathematician and astronomer Alhacen (Abu Ali al-Hasan ibn al-Hasan ibn al-Haytham) re-discovers optics and describes, in his treatise Kitab al-Manazir, "Book of Optics", a working model of what was to eventually become known as the camera obscura. He builds and uses one and becomes the first scientist to observe an eclipse of the sun by this method.

970

The astronomer Abu'l Wefa lays the foundations of trigonometry, a major help with astronomical calculations.

984

Abu Sa'd al-Ala' ibn Sahl (Ibn Sahl), an Arabian mathematician and optics engineer associated with the court of Baghdad. Wrote a treatise On Burning Mirrors and Lenses in which he set out his understanding of how plano-convex and biconvex lenses, and parabolic and ellipsoidal mirrors bend and focus light. He was credited with discovering the law of refraction, nowadays usually called Snell's law.

1000

Mokattam observatory built in Egypt for al-Hakim bin-Amr Allah

1006

Chinese astronomers record short-lived star.

1023

The Hamadan observatory was constructed

1030

Treasury of Optics by Ibn al-Haytham of Egypt Alhazen

1054

Chinese record a supernova that produces the Crab Nebula. Chinese astronomers observed a supernova that was visible in the daytime, they call it the "guest star". The matter blasted outward by the supernova, in the constellation Taurus later became observable as the Crab Nebula.

1074-92

Malikshah observatory at Isfahan used by Khayyam

1119-25

Cairo al-Bataihi observatory built for al-Afdal

1200

Establishment of first universities in Europe. The development of astronomy was aided by the birth of universities at Bologna, Oxford, Paris, and a few other European cities.

1230-1235

Robert Grosseteste describes the use of 'optics' to "...make small things placed at a distance appear any size we want, so that it may be possible for us to read the smallest letters at incredible distances..." in his work "De Iride".

1252-72

Alphonsine tables recorded. A set of tables giving the positions of the Sun, Moon, and planets, published under the patronage of Alfonso X (1223-1284), King of Léon and Castile, who had assembled, at Toledo, many of the world's leading astronomers. The tables were calculated by a team of astronomers using the principles set out by Ptolemy in "The Almagest" but incorporating more recent observations. They remained the standard in Europe for nearly 400 years, until superceded by the work of Johannes Kepler.

1259

Building of the Maragha Observatory of Nasir al-Din al-Tusi under Khan Hulagu. The Khan allocated 2,000 dinars for the construction of an Observatory which would be the largest in the East. Construction began in 1259 and was carried out primarily by Mangu Urdi and his son, Mahmud.

1266

Roger Bacon apparently documents the use of a telescope in his treatise Opus Majus, using terms very similar to his mentor, Robert Grosseteste.

1279

"The Terrace for Managing Heaven" - Beijing observatory built for Zhang Wenqian, Wang Xun and Guo Shoujin; paid for by Khublai Khan. The instruments designed by Wang Xun and Guo Shoujin and built by Nepalese craftsman Arniko. For nearly six hundred years, through Ming and Qing dynasties and on well after the Xinhai Revolution (1911), this location has been used as an astronomical observatory. Nowadays eight large bronze implements for viewing the heavens are arrayed on the top of the museum's tower; these date from the Qing dynasty, and were erected on the instruction of emperor Qianlong of the Qing dynasty. There is a three-level exhibition hall devoted to China's ancient astronomical researches which includes a stone-carved star map from Suzhou, as well as an astronomical map from the ceiling of Longfu Temple. In another room are described some 150 early methods of calculating calendars. There are ancient and medieval astronomical water clocks along with contemporary astronomical clocks on display.

Witelo writes Perspectiva, "Optics" incorporating much of Kitab al-Manazir, where amongst other things, he described a method of machining parabolic mirrors from iron and carried out careful observations on refraction.

1300

Dante describes medieval picture of universe in "Divine Comedy". Dante's picture of the universe has the Earth at its center, surrounded by the spheres of the Moon, Sun, planets, the fixed stars, a crystalline sphere and, finally, paradise.

The Fourteenth & Fifteenth Centuries

1330

Jean Buridan develops the impetus theory of motion. Buridan's theory of motion was remarkable in that it contradicted the established ideas of Aristotle.

1340

The English logician, William of Occam announces the principle of "Occam's Razor". The principle states that the explanation of any phenomenon should make as few assumptions as possible, eliminating, or "shaving off," those that make no difference in the observable predictions of the explanatory hypothesis or theory. i.e. If you have two possible explanations in any given situation, if you are having difficulty in deciding between them - choose the simpler explanation. The principle is often referred to as the "Law of succinctness".

1350

Oresme describes "Galilean" relativity. Oresme pointed out that we perceive only relative motion and that the daily motion of the stars could be explained either by the rotation of the Earth or the rotation of the celestial sphere.

1417

Speculum Planetarium constructed by Simones de Selandia

1420

The construction of an observatory at Samarkand; used profficiently by Ulugh Beg in the creation of a star catalogue

1442

The Ancient Beijing Observatory much expanded. It is located on the southeast corner of Jianguomen Street in Beijing. Originally started, in the Guo Shoujing (1231-1316) period of the Yuan dynasty to explore the heavens. It took on the scale and layout you can see today and was equipped with such traditional instruments as the armillary sphere, the abridged armilla, celestial globe on the observatory platform, as well as the guibiao, sextant, water clock and theodolite. The Observatory has a phenomenal collection of records going back to 1300BC, including...

• The earliest records of Sun spots, dating from 28 BC
• The earliest supernova record, dating from 14 BC
• A record of the supernova in 1054, now generally associated with the Crab Nebula
• 700 meteorite records
• Some of the oldest star maps, dating from the Song Dynasty (1247). These show 1400 stars
• The earliest eclipse records, dating from 1300 BC in the Yin Dynasty
• There are also around 1000 records of eclipses up to the end of the Qing Dynasty
• The earliest record of a comet, dating from 613 BC
• In total there are 360 Records of Comets from Yin Dynasty up until 1911
• 31 records of Halley's Comet

1460

Purbach proposes that the solar spheres were composed of transparent crystal.

1465

Johannes Müller von Königsberg, called Regiomontanus (1436-1476), arguably the most important astronomer of the fifteenth century. He constructed an astrolabe, composed works on trigonometry and the armillary sphere, made his own astronomical observations. It is often said, with some justification, that Regiomontanus set the agenda for the reform of astronomy to which Copernicus, Tycho Brahe and Kepler all contributed. One of his most important efforts was to buy one of the "new" printing presses and produce astronomical tables relatively quickly and cheaply.

1467-71

Observatory built at Oradea, Hungary for Matthias Corvinus

1472

Nuremberg observatory built

1500

Leonardo da Vinci makes a sketch of a flying machine.

The Sixteenth Century

1504

Columbus uses lunar eclipse prediction to influence Arawaks. From his almanac, Columbus knew that a lunar eclipse would occur on February 29. He impressed the Arawaks with his accurate prediction that the Moon would rise "inflamed with wrath".

1512

Nicolaus Copernicus published Commentariolus.

1521

The Magellanic Clouds (distant galaxies) were first observed by Magellan

1520-1559

English mathematician and surveyor Leonard Digges possible inventor of both reflecting and refracting telescopes.

1539

Martin Luther calls Nicolaus Copernicus a fool.

1540

Beginning of the Copernical Revolution. Peter Apian writes the "Astronomicum Caesareum" (The Emperor's Astronomy) describes the mechanics of an earth-centered universe.

1543

Copernicus revives Aristarchus' ideas (300 BC) and publishes De revolutionibus - "On the Revolutions of the Celestial Spheres". This was his description of his heliocentric model of the solar system, and was published two months before his death. He is the first European to claim that the Earth is not the center of the universe.

1550

Fracastoro developed a model of the solar system with 79 spheres.

1560

The building of Kassel observatory under Landgrave Wilhelm IV of Hesse

1572

Tycho Brahe sees a supernova in the Cassiopeia constellation and proves that it is just as far away as the other stars. This established his reputation as an astronomer.

1575-80

The building of Istanbul observatory of al-Din under Sultan Murad III

1576

Tycho Brahe builds the Royal Danish Astronomical Observatory - Uraniborg and begins his important observations from the island of Hven, where he formulates his own astronomical system and produces his catalog of planets and stars.

The English astronomer Thomas Digges presents the idea that the stars are at very different and very large distances from the Earth. He has a description of a device that indicates that he constructed a telescope (called PERSPECTIVE GLASS from the Latin perspicere, to see through). It could also have been his father Leonard who made the invention in the 1550s.

1580

Tycho carries out best pre-telescopic observations ever. Tycho's observations, made using specially built instruments, were the most accurate ever made with the naked eye. Tycho also invented his own geocentric model of the solar system.

1582

Pope Gregory XIII introduces his calendar - still in use today. Dates were re-calculated by following the observations of Christopher Clavius and Johannes Kepler, and was changed when Pope Gregory XIII decreed that the day after October 4, 1582 would be October 15, 1582. He issued the papal bull "Inter Gravissimas" to promulgate the new calendar on February 24, 1582. On October 15, 1582, this calendar replaced the Julian calendar, in use since 45 BC, and has become universally used today. As a point of interest, the last "western" country to adopt the Gregorian Calendar was Greece in 1923!

1584

Filippo Giordano Bruno publishes his books, Cena de le Ceneri - "The Ash Wednesday Supper" and De l'Infinito, Universo e Mondi - "On the Infinite Universe and Worlds". Because he claimed in his books that the earth was not the centre of the universe Bruno spent eight years in chains in the Castel Sant'Angelo, where he was routinely tortured and interrogated by the inquisition, until his trial. He would not recant. Immediately after the death sentence was handed down by the Roman Catholic Church, he was tortured further. On February 19, 1600, he was driven through the streets of Rome, stripped of his clothes and burned at the stake.

1596

David Fabricius discovers Mira, the first known periodic variable star, now known as Omicron Ceti. It is the prototype for an entire class of stars known as "Mira-type variables." Although once like our Sun, Mira is now at the end of its life, and has evolved into a cool red giant star that is highly variable in brightness.

1596

Tycho Brahe completes his catalog of planets and stars.

1600

Galileo begins experiments with falling and rolling bodies. Galileo's experiments led him to conclude that once something is set in motion it will remain in motion unless something stops it. This contradicted earlier ideas that said only rest was a natural state.

Giordano Bruno burned at stake. Bruno was tried before the Inquisition and burned for heresy. Among his heresies was the idea that there were Earth-like, inhabited planets orbiting the infinitely many stars.

Prague observatory in Benátky nad Jizerou by Tycho Brahe.

William Gilbert proposes Earth has dipole magnetic field. Gilbert proposed that the Earth acts like a big magnet whose field aligns the small magnet used as a compass needle.

The Seventeenth Century up to 1682

1603

Johann Bayer publishes his star chart. He uses Greek letters to indicate the luminosity of the stars. He publishes "Uranometria" that introduced a new way of designating stars by assigning Greek letters to each of them.

1604

Johannes Kepler sees a supernova. As of February 1998, this was the last supernova which was definitely observed in our Milky Way Galaxy. First noticed on October 9, 1604, when it was already brighter than all stars in the sky. Seen by Brunowski in Prague, Altobelli in Verona, Clavius in Rome, and Capra and Marius in Padua. Kepler was advised of it by Brunowski, but didn't see it until October 17.

1608

Hans Lippershey, a Dutch lensmaker, applies for a patent for the design of a telescope. Several other people make similar claims around the same time, such as Jacob Metius and Zacharias Janssen.

1609-10

Galileo Galilei builds his first optical refracting telescope Galileo Galilei makes his own improved version of Lippershey's telescope, calling it at first a "perspicillum," and then using the terms "telescopium" in Latin and "telescopio" in Italian. Telescopes using one convex and one concave lens are often termed 'Galilean'. Galileo observes for the first time craters on the Moon, He called the dark regions of the Moon maria, the Latin word for seas. He discovers four largest satellites of Jupiter. Galileo found that Jupiter is orbited by four large satellites, now called, collectively, the Galilean satellites. This proved that at least some celestial bodies didn't orbit the Earth. He also observes the phases of Venus. Galileo's found that Venus shows all the phases from new to full. This observation was incompatible with the Ptolemaic model of the solar system.

Kepler discovers laws of planetary motion. Working with Tycho's observations, Kepler discovers the shapes of planetary orbits, how the speed of a planet varies as it orbits the Sun, and the relationship between orbital distance and orbital period. Sunspots and their rotation with the Sun were discovered independently by Galileo Galilei, Johann Fabricius (Holland) and Christopher Scheiner. All used the recently invented telescope, and Scheiner apparently introduced the safe method of projecting the Sun's image on a flat surface. Johann Kepler (1571 1630), using Tycho's observations, formulates his first two laws of planetary motion (3rd law in 1619).

1609

Galileo Galilei begins astronomical observations with the refracting telescope he developed.

Johannes Kepler publishes Astronomia Nova - "New Astronomy", that describes his first two laws of planetary motion. He also pubishes Tycho Brahe's calculation of the orbit of Mars.

1610

Galileo Galilei, using his new telescope, discovers the phases of Venus, four large moons of Jupiter Io, Europa, Ganymede and Callisto (now known as the Galilean moons), and mountains on the Moon. As another result of his observations, he proposes that the Milky Way is composed of many faint stars

1611

Johannes Fabricius identifies sunspots with a telescope. However, they had been described in ancient Chinese sources.

Johannes Kepler describes the optics of lenses (see his books Astronomiae Pars Optica and Dioptrice), including a new kind of astronomical telescope with two convex lenses (the 'Keplerian' telescope).

1612

Simon Marius independently rediscovered the "Nebula in the Girdle of Andromeda", actually the Andromeda Galaxy (M31), on December 15, 1612, and was the first to observe it with a (very moderate) telescope; he described it as looking like a "flame seen through horn." He was not aware that this object had been seen previously by medieval Persian astronomers, and described by Al Sufi as early as 964 AD.

1613

Galileo Galilei discovers and publishes work on sunspots.

1616

The Catholic church, in its infinite wisdom, bans the reading of "De Revolutionibus".

Niccolo Zucchi constructs a reflecting telescope.

1619

Kepler publishes De Cometis - "On Comets" and Harmonice mundi - "Harmony of the World", in which he announces respectively his observations on the three comets of 1618, and his third law of planetary motion.

1620

Francis Bacon suggests that Earth's continents move about. Bacon noticed that the eastern and western shores of the Atlantic were parallel and could be fitted together.

1630

Christoph Scheiner had begun observing sunspots in March or April 1611and after over 15 years of continuous study, helped by the Helioscope which he constructed himself, published a book called "Rosa Ursina" in which he proposed that sunspots were minor planets. In this book he started with a vicious attack on the observations of Galileo, who of course hit back in his "Dialogues". Since Scheiner was a Jesuit in good standing this did not improve matters between Galileo and the Roman Catholic church.

Descartes develops concept of inertial motion. Descartes believed that all motion resulted from collision with particles called "corpuscles". In the absence of such collisions, a body remains at rest. An object in motion continues to move in the same direction at the same speed.

1632

Galileo publishes "Dialogo sopra i due Massimi Sistemi del Mondo" (The Dialogue). Although superficially a balanced debate about the merits of the geocentric and heliocentric models of the solar system, was in fact a powerful argument for the ideas of Copernicus, in which he supports the view that the planets circled the sun.

1633

The Catholic Church strikes again - Galileo's ideas are condemned, he is tried by the Inquisition. Galileo Galilei was 68 years old and sick. Threatened with torture, he publically confessed that he had been wrong to have said that the Earth moves around the Sun. Legend then has it that after his confession, Galileo quietly whispered "And yet, it moves". Fortunately, unlike many less famous prisoners, he was not incarcerated but was allowed to live under house arrest in his house outside of Florence. He was near one of his daughters, a nun. Until his death, he continued to investigate other areas of science.

The world's first State observatory is established in Leiden, Holland.

Construction of Leiden University Observatory

1638

John Phocylides Holwarda determines that Mira Ceti is not a nova but a variable star

1640-1720

Maunder minimum. This is the name given to the period roughly from 1645 to 1715, when sunspot activity hit a very low level. This was carefully noted by solar observers of the time. It was named long after for the solar astronomer E.W. Maunder who revealed the low level of sunspots during that period by studying records from those years. During one particular 30-year period within the Maunder Minimum astronomers observed only about 50 sunspots, as opposed to a more typical 40,000-50,000 - quite a difference! It is interesting to note that this was also a time of cold climate in Western Europe and North America.

1641

Danzig/Gdansk observatory of Jan Hevelius is built.

William Gascoigne invents telescope cross hairs

1642

Galileo dies. The world's second State observatory, the Copenhagen University Royal observatory is founded in Rundetaarn, Denmark.

1644

Rene Descartes proposes the first of the evolutionary theories of the formation of the solar system.

1647

Johannes Hevelius (Latin), also called Johannes Hewel, Johann Hewelke, Johannes Höwelcke in German, or Jan Heweliusz (in Polish), (1611-1687), was a protestant councilor and mayor in Danzig (Gdan'sk), Polish-Lithuanian Commonwealth. As an astronomer he gained the reputation of "the founder of lunar topography" and made the first mostly accurate map of the Moon.

1650

Jean Riccioli discovered that the star Mizar is a binary. Christiaan Huygens produces his design for a compound eyepiece.

1651

Riccioli begins naming lunar craters after famous philosophers and scientists.

1654

Bishop Ussher uses Bible to calculate age of Earth. See above.

1655

Dutch mathematician Christiaan Huygens (1629-1695) studied law and mathematics at the University of Leiden. His first publication in 1651 "Cyclometriae" showed the fallacy in methods proposed by Gregory of Saint-Vincent, who had claimed to have squared the circle. Huygens soon turned his attention to lens grinding and telescope construction and in 1654 he devised a new and better way of grinding and polishing lenses. Using one of his own lenses, Huygens detected, in 1655, the first moon of Saturn. He realizes that the "appendages" of Saturn are rings. Huygens watched the appendages disappear in 1665 and reappear several years later and realized that they were really flat rings that disappeared when viewed edge on.

1656

Christiaan Huygens invents a pendulum clock.

1657

Cyrano de Bergerac publishes "Voyage Dans La Lune" (Voyage to the Moon). According to Arthur C. Clarke, Cyrano must be credited both for first applying the rocket to space travel and, for inventing the ramjet.

1659

Anglo-Irish physicist and chemist Robert Boyle develops an air pump for creating vacuums, confirms Galileo's view that bodies fall in a vacuum at the same rate, regardless of weight. He also discovers that sound does not travel in a vacuum.

1659

Christiaan Huygens records features on the surface of the planet Mars.

1660

Robert Hooke of London claims he invented and applied the hairspring to the balance wheel. For a long time, the invention is widely credited to Christiaan Huygens and Abbé d'Hautefeuille who simultaneously developed the use of a hairspring with the balance wheel in 1674. But in February 2006, amazingly, a long-lost copy of Hooke's handwritten notes from several decades' Royal Society meetings was discovered in a cupboard in Hampshire, and the balance-spring controversy appears by evidence contained in those notes to be settled in favor of Hooke's claim.

1663

Scottish mathematician James Gregory designs a reflecting telescope with paraboloid primary mirror and ellipsoid secondary mirror. Construction techniques at the time could not make it, and a workable model was produced only about 60 years later. The design is known as 'Gregorian'.

1664

Isaac Newton experiments with gravity.

1665-7

Newton discovers law of universal gravitation. When Cambridge University was closed by the plague, Newton spent most of the next two years at his family farm. During this period he made fundamental discoveries in optics, discovered the law of universal gravitation, and invented differential and integral calculus.

1665

Giovanni Cassini discovers Great Red Spot of Jupiter. Although its size and darkness have changed with time, the Great Red Spot has been continuously present since the time of Cassini's discovery. The spot was also observed and noted by Robert Hooke.

1666

Robert Hooke shows that a central force leads to orbital motion. Hooke used a pendulum to demonstrate to the members of the Royal Society that in order to stay in orbit, the planets must be continually pulled toward the Sun.

Giovanni Cassini measured the period of rotation of Mars and identified its polar ice caps.

1667

Construction begins of the Paris Observatory, or Observatoire de Paris. The national astronomical observatory of France, under the direction of the Academy of Sciences. It was founded by Louis XIV at the instigation of J. B. Colbert, Gian Domenico Cassini was the first of four generations of his family to hold the post of director of the observatory.

1668

Isaac Newton produces his own design of reflecting telescope using a paraboloid primary mirror and a flat diagonal secondary mirror. This design is termed the 'Newtonian'.

James Gregory makes the first realistic estimate of the distances of the stars. Gregory assumed that the other stars were just as bright as the Sun and then calculated how distant they had to be to match their apparent brightnesses.

1669

Italian astronomer Geminiano Montanari discovers the brightness of the star Algol is variable.

Isaac Newton in England and Gottfried Wilhelm Leibrniz in Germany determine the principles of calculus at the same time. (The name is derived from the Latin word for pebble, referring to the use of pebble for counting.)

Robert Hooke observes that the star Gamma Draconis has a parallax of 30 seconds of arc.

1670

First nova observed by Western astronomers (Johannes Hevelius and, independently, Pere Dom Voiture Anthelme)

1671

The Paris observatory is established.

1672

Jean Richer, a French astronomer, derives the parallax of Mars, and uses Kepler's 3rd law to obtain the first modern estimate of the astronomical unit, within abut 30%.

Laurent Cassegrain, produces a different design of reflecting telescope to Gregory, again, well ahead of manufacturing techniques of the time using a paraboloid primary mirror and a hyperboloid secondary mirror. The design, named 'Cassegrain', is still, in 2006, used in astronomical telescopes.

1674

Robert Hooke produces an experimental model of a telescope to the Gregorian design.

1675

Cassini identifies a gap in the rings of Saturn, now called the "Cassini Division".

Leibniz determines integral and differential calculus.

Christian Huygens developed the balance wheel and spring assembly - still in use in some of today's wrist watches - and patents the pocket watch.

Foundation of the Royal Greenwich Observatory of England, now called The Royal Observatory, Greenwich. Commissioned by King Charles II. At this time the king also created the position of Astronomer Royal (initially filled by John Flamsteed), to serve as the director of the observatory and to "apply himself with the most exact care and diligence to the rectifying of the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting of the art of navigation."

1676

Ole Rømer, a Danish astronomer working in Paris, a French astronomer, tabulates the eclipses of Jupiter's innermost moon Io. His observations using the delay in lunar eclipses in connection with Jupiter to measure the speed suggest that light has a great but finite velocity.

1678

Christiaan Huygens discovers the polarization of light.

First major systematic Southern sky survey compiled by Edmund Halley

1680

First publication of "Old Moore's Almanack", which later becomes known as "Vox stellarum".

Isaac Newton explains the relationship between mass, gravity, and acceleration.

1682

Edmond Halley discovers and predicts return of Comet Halley. Halley noted that comets with similar orbits had appeared in 1456, 1531, 1607, and 1682. He proposed that these were all the same comet and that it would return in 1758 or 1759 - which it did.