Gan De
Encyclopedia
Gan De was a Chinese
astronomer
/astrologer
born in the State of Qi also known as the Lord Gan (Gan Gong). Along with Shi Shen
, he is believed to be the first in history known by name to compile a star catalogue
, preceded by the anonymous authors of the early Babylonian star catalogues
and followed by the Greek Hipparchus
who is the first known in the Western tradition to have compiled a star catalogue.
has claimed that this was a naked-eye observation of Ganymede
in the summer of 365 BC, long before Galileo Galilei
's celebrated discovery of the same in 1610 (all four of the brightest moons are technically visible to the unaided eye, but in practice are normally hidden by the glare of Jupiter). By occluding Jupiter itself behind a high tree limb perpendicular to the satellites' orbital plane
to prevent the planet's glare from obscuring them, one or more of the Galilean moons
might be spotted in favorable conditions. However, Gan De reported the color of the companion as reddish, which is puzzling since the moons are too faint for their color to be perceived with the naked eye. Shi and Gan together made fairly accurate observations of the five major planets.
into 365°, as a tropical year has 365 days. At the time, most ancient astronomers adopted the Babylon
division where the celestial sphere is divided by 360°.
, Gan De's work possesses high scientific value. He wrote two books, the Treatise on Jupiter and the 8-volumes Treatise on Astronomical Astrology, both of which have been lost. Gan De also wrote the Astronomic star observation (天文星占, Tianwen xingzhan).
It can be seen on the quotations under Shiji (volume 27) and Hanshu (volume 26), but was preserved mostly in the Treatise on Astrology of the Kaiyuan Era
.
In 1973, a similar catalogue by him and Shi Shen was uncovered in Mawangdui
. It was arranged under the name of Divination of Five Planets. It records the motion of Jupiter, Saturn, Venus and other planets in their orbits between 246 BC and 177 BC.
Chinese people
The term Chinese people may refer to any of the following:*People with Han Chinese ethnicity ....
astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
/astrologer
Astrologer
An astrologer practices one or more forms of astrology. Typically an astrologer draws a horoscope for the time of an event, such as a person's birth, and interprets celestial points and their placements at the time of the event to better understand someone, determine the auspiciousness of an...
born in the State of Qi also known as the Lord Gan (Gan Gong). Along with Shi Shen
Shi Shen
Shi Shen was a Chinese astronomer and contemporary of Gan De born in the State of Wei, also known as the Master Shi Shen .-Observations:...
, he is believed to be the first in history known by name to compile a star catalogue
Star catalogue
A star catalogue, or star catalog, is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, and this article covers only some...
, preceded by the anonymous authors of the early Babylonian star catalogues
Babylonian star catalogues
Babylonian astronomy collated earlier observations and divinations into sets of Babylonian star catalogues, during and after the Kassite rule over Babylonia. These star catalogues, written in cuneiform script, contained lists of constellations, individual stars, and planets...
and followed by the Greek Hipparchus
Hipparchus
Hipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...
who is the first known in the Western tradition to have compiled a star catalogue.
Observations
Gan De made some of the first detailed observations of Jupiter in recorded history. He described the planet as "very large and bright". In one of his observations on Jupiter, he reported a "small reddish star" next to Jupiter. The historian Xi ZezongXi Zezong
Xi Zezong was a Chinese astronomical historian. He is best known for his finding in Ancient Chinese history of the reference to Ganymede being visible to the human eye by ancient astronomer Gan De, before it was officially recognised by the west...
has claimed that this was a naked-eye observation of Ganymede
Ganymede (moon)
Ganymede is a satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively...
in the summer of 365 BC, long before Galileo Galilei
Galileo Galilei
Galileo Galilei , was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism...
's celebrated discovery of the same in 1610 (all four of the brightest moons are technically visible to the unaided eye, but in practice are normally hidden by the glare of Jupiter). By occluding Jupiter itself behind a high tree limb perpendicular to the satellites' orbital plane
Orbital plane
Orbital plane may refer to:*Orbital plane *In anatomy, it refers to a specific area of the maxilla...
to prevent the planet's glare from obscuring them, one or more of the Galilean moons
Galilean moons
The Galilean moons are the four moons of Jupiter discovered by Galileo Galilei in January 1610. They are the largest of the many moons of Jupiter and derive their names from the lovers of Zeus: Io, Europa, Ganymede and Callisto. Ganymede, Europa and Io participate in a 1:2:4 orbital resonance...
might be spotted in favorable conditions. However, Gan De reported the color of the companion as reddish, which is puzzling since the moons are too faint for their color to be perceived with the naked eye. Shi and Gan together made fairly accurate observations of the five major planets.
Planetary periodic comparisons
| Planet | Period | Predictions by Gan and Shi | Modern day calculation |
|---|---|---|---|
| Jupiter | sidereal period | 12 years | 11.862615 years Julian year (astronomy) In astronomy, a Julian year is a unit of measurement of time defined as exactly 365.25 days of 86 400 SI seconds each, totaling 31 557 600 seconds. The Julian year is the average length of the year in the Julian calendar used in Western societies in previous centuries, and for which the unit is... |
| Venus | synodic period | 587.25 day Day A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun... s |
583.92 days |
| Mercury | synodic period | 136 days | 115.88 days |
Celestial comparisons
Shi Shen and Gan De divided the celestial sphereCelestial sphere
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with the Earth and rotating upon the same axis. All objects in the sky can be thought of as projected upon the celestial sphere. Projected upward from Earth's equator and poles are the...
into 365°, as a tropical year has 365 days. At the time, most ancient astronomers adopted the Babylon
Babylon
Babylon was an Akkadian city-state of ancient Mesopotamia, the remains of which are found in present-day Al Hillah, Babil Province, Iraq, about 85 kilometers south of Baghdad...
division where the celestial sphere is divided by 360°.
Books
As the earliest attempt to document the sky during the Warring States PeriodWarring States Period
The Warring States Period , also known as the Era of Warring States, or the Warring Kingdoms period, covers the Iron Age period from about 475 BC to the reunification of China under the Qin Dynasty in 221 BC...
, Gan De's work possesses high scientific value. He wrote two books, the Treatise on Jupiter and the 8-volumes Treatise on Astronomical Astrology, both of which have been lost. Gan De also wrote the Astronomic star observation (天文星占, Tianwen xingzhan).
It can be seen on the quotations under Shiji (volume 27) and Hanshu (volume 26), but was preserved mostly in the Treatise on Astrology of the Kaiyuan Era
Treatise on Astrology of the Kaiyuan Era
The Treatise on Astrology of the Kaiyuan Era is a Chinese astrology encyclopedia compiled by the lead editor Gautama Siddha and numerous scholars from 714 to 724 AD during the Kaiyuan era of Tang Dynasty. The compilation is attributed to the author by 729. Its full title is regarded as the Great...
.
In 1973, a similar catalogue by him and Shi Shen was uncovered in Mawangdui
Mawangdui Silk Texts
The Mawangdui Silk Texts are texts of Chinese philosophical and medical works written on silk and found at Mawangdui in China in 1973. They include some of the earliest attested manuscripts of existing texts such as the I Ching, two copies of the Tao Te Ching, one similar copy of Strategies of the...
. It was arranged under the name of Divination of Five Planets. It records the motion of Jupiter, Saturn, Venus and other planets in their orbits between 246 BC and 177 BC.
See also
- Chinese star mapsChinese star mapsChinese star maps are usually directional or graphical representations of Chinese astronomical alignments. Throughout the history of China, numerous star maps have been recorded. This page is intended to list or show the best available version of each star map. Star catalogues are also listed...
- HipparchusHipparchusHipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...
- Nicolaus CopernicusNicolaus CopernicusNicolaus Copernicus was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology which displaced the Earth from the center of the universe....
- Galileo GalileiGalileo GalileiGalileo Galilei , was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism...