26 terms

Chinese astronomy

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oracle bones (Shang; 1500 BC)
primarily the scapulae of oxen and turtle shells

inscribed with a primitive version of the Chinese writing

Several permanent stars have been identified from these records and there are possible sightings of `new' stars. Lunar eclipses were noted

standard method of divination is that cracks were introduced into the bones or turtle shells by heating them, and the cracks were then subjected to interpretation
lunar mansions ( xiu; 28)
28 lunar mansions or xiu, presumably in reference to the sidereal month

sections of the celestial sphere, from pole to pole, with varying width
equatorial astronomy
Before the Han Dynasty, the Chinese developed a method of mapping out the celestial sphere using equatorial coordinates.
asterism
stars in smaller groups than our constellations, called asterisms.
astronomical directorate
One division was for the imperial astronomer, who was in charge of observations. The sky was closely followed because of the belief that there were omens of importance to the state. Had 2 taking notes independently at the same place

Another division was that of the imperial `astrologer,' who was in charge of the interpretation of celestial events.

Another division was in charge of keeping time by water clocks.
chi
length of measurement close to a foot
sunspots
Han Dynasty observations of sunspots are the earliest known observations of sunspots. The spots can be observed when the sun is behind thin clouds, or through a jade disk
gnomon
A standard gnomon (rod) used to measure solar shadows was 8 chi long

Gnomons were used to accurately measure the maximum altitude of the sun, including the extremes on the summer and winter solstices. The angle between the sun and the equator on those dates gives the obliquity of the earth. Using Chinese observations going back to Han times, Laplace showed in the 1700's that the earth's obliquity is slowly changing. It is currently becoming smaller.
du (365 1/4 in a circle)
There were 365 1/4 du in 360 degrees, demonstrating a good knowledge of the solar year.

Positions were given as the number of du from the celestial pole and from the edge of the lunar mansion in which the event occurred.
flat earth cosmology
The kai tian school discussed the structure of the earth and heavens.

Using the knowledge that the altitude of the sun changed with position along a N/S line in China, they determined the distance to the sun in a flat earth cosmology.

This distance was, of course, way too small. We now know that the sun is very distant, and the change of its altitude with latitude is due to the spherical shape of the earth.
calculation of solar distance
used gnomon rods to measure altitude of sun

Using the knowledge that the altitude of the sun changed with position along a N/S line in China, they determined the distance to the sun in a flat earth cosmology. This distance was, of course, way too small.
xuanye - infinite emptiness, Sun as body in space
The xuanye school is sometimes called the school of infinite emptiness.

The bodies were regarded as condensed vapors.

This view was supported by the observation of changing spots on the sun.
60-name day cycle (10 x 12 days)
During the Shang Dynasty, the Chinese had in place interlocking cycles of 10 days and 12 days; together, these made a cycle of 60 days.
60-name year cycle (10 x 12 years)
At some point after the introduction of the 60 day cycle, the Chinese starting using a 60 year cycle, made up of 10 year and 12 year components. Twelve years is also a good estimate of Jupiter's sidereal period, so its motion relative to the background stars was carefully followed. At the present time, the use of the 10 year cycle has dropped away, leaving only the 12 year cycle. There are animals associated with each year of the cycle and the Chinese years are labeled with Year of the Rat, etc.
hun tian - celestial circles
The hun tian school emphasized the motion of celestial objects in circles across the sky. They realized the apparent rotation of objects about the celestial pole and developed instruments that took advantage of this fact for determining celestial positions, such as an armillary sphere
armillary sphere
The basic structure of an armillary sphere is an axis pointed toward the celestial pole, a movable ring that turns on this axis and another, perpendicular, ring. The instrument can be used to obtain positions in celestial coordinates.
naked eye supernova
every few 100 years
supernova of 1054 - Crab Nebula
Of special interest is SN 1054, which has been identified with the Crab Nebula. In 1968, the Crab Nebula was found to contain a pulsar, a very rapidly rotating neutron star. The pulsar gradually spins down, releasing power for the light that we see from the nebula. The data determined from the Chinese observations show that the pieces of exploded star have accelerated since the time of the explosion. Power from the pulsar is the likely source of the power.
guest stars
Chinese observations of supernovae before 1500 are unparalleled elsewhere in the world. The fact that they were regarded as omens resulted in a lot of attention being lavished on new stars, or "guest stars."
supernova light echo
a light echo is produced when a sudden flash or burst of light, such as that observed in novae, is reflected off a source and arrives at the viewer after a considerably longer duration than it otherwise would have taken with a direct path
Jupiter (12 year sidereal period)
Chinese starting using a 60 year cycle, made up of 10 year and 12 year components. Twelve years is also a good estimate of Jupiter's sidereal period, so its motion relative to the background stars was carefully followed.
Temple of Heaven (Beijing)
The temple of heaven is to the south of the Forbidden City, where the emperor lived. At the time of the winter solstice, the emperor would move with a procession to the temple of heaven in order to carry out rituals. The aim was to be sure that the sun reversed its course and began to move northward in the sky. The Forbidden City itself has a path through it on a N/S axis that sets the overall orientation for the city. Walking on the path was generally forbidden, except for 1) the emperor, 2) the empress on the day that she married, and 3) the 3 high scorers on an annual exam given to determine who would get government positions.
dynastic histories
Shang Dynasty (about 1600-1100 BC)

The Shang Dynasty had been largely in the realm of myth, but around the turn of the century (1900), `oracle bones' with a written record were found in the fields of Chinese farmers.
During the Shang Dynasty, the Chinese had in place interlocking cycles of 10 days and 12 days; together, these made a cycle of 60 days.

Han Dynasty (about 200 BC - 200 AD)

The Han dynasty was preceded by the reign of Emperor Qin, who unified a large part of China. China then covered a large area, including about 20 degrees in latitude. Records were brought to the capital from throughout China, so that differences in astronomical observations at different places could play a role.

Before the Han Dynasty, the Chinese developed a method of mapping out the celestial sphere using equatorial coordinates.

During the Han dynasty, there were the beginnings of cosmological speculation; debates took place between 3 competing schools of thought.
changing Earth's obliquity
Gnomons were used to accurately measure the maximum altitude of the sun, including the extremes on the summer and winter solstices. The angle between the sun and the equator on those dates gives the obliquity of the earth. Using Chinese observations going back to Han times, Laplace showed in the 1700's that the earth's obliquity is slowly changing. It is currently becoming smaller.
changing Earth's rotation
from observations of lunar occultations of the planets.
Han dynasty calendar (initially 365 1/4 day)
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