Ancient Astronomy

The ancients of Greece and Babylon record the risings and settings of stars on parapegma to help them reckon the time of the year.

Autocylus' On the Moving Sphere and On Risings and Settings are the oldest surviving works of Greek mathematical astronomy.

Alexander the Great Conquers Persia and gains more direct access to their scientific knowledge.

Alexander the Great dies of fever and his empire splits. His general, Ptolemaios I establishes a Greek-speaking dynasty in Egypt. Astronomical research does well in this kingdom, particularly at Alexandria

The Babylonian astronomer's work survived as fragments inherited by Greek and Roman writers. He is attributed with an initial theory and description of lunar phases.

Timocharis and Aristyllos take the some of the earliest surviving measurements of the positions and motions of heavenly bodies. Their work helps later astronomers deduce such facts as the precession rate.

Eratosthenes was a great intellectual of his day and his crowning work is his Geography. The work introduces geometrical methods to geography and uses gnomonics to generate one of the earliest measurements of Earth's size.

The poet Aratus composes a poem that explains the arrangement and qualities of the constellations. The poem also gives weather signs, some of which are in relation to the movements of the stars.

Aristarchus is creditted with two major achievments: in his On the Sizes and Distances of the Sun and the Moon, he geometrically determines the distances between and dimensions of the sun, moon and earth. Furthermore he also discovered the Earth's dual motion, meaning Earth's simultaneous revolution about the sun and rotation about its axis.

Hypsicles work gives historians insights into the trigonometry of Greece during its astronomical peak. His book, Anaphorikos/Rising Times, shows how trigonometry is used to generate a table of ascensions.

A theory of the motion of the sun, which explains the irregularity of the seasons and the uniform circulation motion of the sun, emerges and is attributed to Hipparchus (this is mostly speculation due to lack of historical evidence on early solar theory).

The first planetary theory originates in Babylon and is eventually adopted by Greece.

Hipparchus discovers the phenomena of precession. While he does not measure it accurately, he does prove that the stars are shifting along the ecliptic very slowly with the passage of time.

Julius Caesar is elected Emperor an takes absolute power during his reign. He institutes the Julian calendar but is famously betrayed and killed in the Senate by those dissatisfied with his rule.

Marcus Vitruvius Pollio writes his X Books on Architecture. Within he describes the necessity of gnomonics in architecture and includes an analemma for constructing sun dials.

Julius Caesar introduces the Julian calendar which persists for 100's of years despite inaccuracies in its time reckoning. It changes throughout its use, reaching a final form in 8 AD and is reformed by Pope Gregory in the 1500s.

Geminus, one of the later Greek astronomers, wrote an elementary textbook called an Introduction to the Phenomena. It contains good, general information about the practice of astronomy and was often used for introductory instruction.

Like Geminus, Cleomedes also wrote an introductory book on astronomy. He entitled it On the Elementary Theory of the Heavenly Bodies. He references the work of Posidonius and Eratosthenes and generally presents the work in the frame of Aristotelian physics.

Marinus is attributed by Ptolemy as having been one of the first scientists to use longitudes and latitudes in his work. He did not use them as extensively as Ptolemy in his analysis of the Phenomena

Ptolemy's work in the Almagest brings the measurements of earlier astronomers such as Hipparchus and Timoachris in order to yield a precession rate. His answer is that the stars shift 1 degree every 100 years, but in reality the rate is 1 degree every 72 years. Ptolemy's rate goes uncorrected for centuries

Ptolemy forever revolutionizes astronomy with his Almagest, a comprehensive guide to the motions and aspects of the heavens according to mostly Aristotelian physics. This becomes the go-to astronomical text for hundreds of years after antiquity and is still esteemed today

Despite the astrolabe having been in use for many years, Theon writes history's first definitive treatise on the astrolabe. It does not survive today but is referenced in later works.

The emperor Constantine, inspired by a vision before a battle, pledges to convert the empire to the teachings of Christ if he won. When he did, Rome became a Christian nation. However, many disbelieve in the vision story and consider the transition to a new religion to be politically motivated

In order to account for precession and a noticeable decrease in the obliquity of the ecliptic over time, the Arab astronomer Thabit ibn Qurra proposes the theory of trepidation. The theory basically states that as time passes the ecliptic actually wobbles back and forth during its annual motions. it is accepted until refuted by Tycho Brahe.

Al Ma'mun takes power in the new city of Baghdad. He establishes a multicultural confluence of scientists called the House of Wisdom. This institution makes Islamic astronomy the dominant form of astronomy in the middle ages.

Commissioned by the King Alfonso X of what is now Spain, these tables were some of the most popular and disseminated tables of obliquity in the medieval astronomical tradition.

The oldest, surviving, English scientific work surfaces in the form of a Treatise on the Astrolabe. The famous Chaucer wrote it for his ten year old son, Lewis.

Georg Hartmann is born and grows up to be one of the most celebrated astrolabe makers of the Renaissance. Aside from making fine ones for royalty, he also made cheap astrolabe kits for people of lesser means.

Copernicus releases a work entitled On the Revolutions of the Heavenly Spheres. This proposes a heliocentric model of the universe and causes a comparable amount of controversy to Darwin's Origin of Species

Starting in the mid-1570's, Tycho Brahe and his apprentices study the heavens at his estate of Uraniborg. Most notably, they correct the precession rate which had been overestimated by the ancients.

The Catholic church under Poper Gregory XIII institutes a permanent reform to correct the Julian Calendar. Do to inconsistencies between the Julian year and the tropical year, the calendar had fallen behind. The day after the reform, rather than being Oct 5th, was Oct 14th. The Gregorian reform also excluded certain leap years, like 1900, which are referred to as common years.

Johannes Kepler sends the practice of astronomy forward by explains the true nature of orbit in space. Rather than the heavenly bodies moving in circles, Kepler proves that orbital paths are elliptical

Isaac Newton is born and during his career completely revolutionizes physics. Among his astronomical achievements are the discovered the laws of universal gravitation and explains the nature of the heavens as a void of empty space inhabited by a swarm of planets, stars and other such bodies.