comprehensive star catalogue, plotting the position of more
than 1,000 stars. A tradition also records that Gan De made
the fi rst observation of Ganymede, a moon of Jupiter, without
a telescope or artifi cial optics of any kind.EARTH SCIENCE
Geology and metallurgy made important advances in the
early Chinese dynasties. Geologists carefully recorded their
discoveries while keeping the practical application of their
knowledge foremost. For example, they constantly compared
rocks and soils above the ground with those found beneath
it. Th e Chinese discovered, for example, that the presence
of hematite, or metallic stones, above ground indicates the
existence of underground veins of iron ore and that the red-
dish mineral cinnabar is a good indicator of gold or mercury
deposits. Th ese observations led to classifi cation systems for
minerals, one of which is found in the Shan hai jing (Th e
Book of Mountains), a work of the fi ft h century b.c.e. Th is
book classifi ed rocks according to their hardness, color, and
shape, and guided metalsmiths in collecting mineral ores and
smelting them into useful fi nished metals.
Ancient Chinese iron miners discovered magnetite, a
rock with magnetic properties. Th is discovery led to the navi-
gational compass, one of the most important technological
breakthroughs in history. Th e Chinese built south-pointing
compasses to guide themselves over land and sea. Th e point-
ers on these devices were commonly spoons or representa-
tions of animals such as frogs. Later the spoons were replaced
by needles, which allowed the compass or pointer much
greater accuracy.
Th e Chinese were also expert in the science of meteo-
rology. Th ey were setting down weather records by the sec-
ond millennium b.c.e. and making daily calculations of
temperature, rainfall amounts, and wind speed and direc-
tion. Th is diligent record keeping brought them knowledge
of the earth’s hydrologic cycle of precipitation and evapora-
tion, which manifests in wind, clouds, and storms to keep the
earth watered and fertile.APPLIED SCIENCE
In all scientifi c endeavors of ancient China, theory and ob-
servation had practical uses. While observing the sun, an
unknown Chinese inventor realized that the sun’s position
can be measured by the length of its shadow. He then cre-
ated the gnomon, a simple vertical pole placed upright to cast
the sun’s shadow. Th e shadow shrinks to its smallest length
at the summer solstice and to its greatest length at the winter
solstice. Th us, using the gnomon, the Chinese measured the
length of the year and marked the beginning of the seasons.
Th e taller the gnomon, the more accurate the measurement;
to raise large gnomons, the Chinese constructed massive
brick structures, many of which still stand. Th e scientist Zu
Gengzhi took the gnomon a step further by adding a hori-
zontal measuring scale and making the device small and light
enough to be carried.Other Chinese breakthroughs include the making of cast
iron and the forging of harder, more durable steel by blowing
oxygen onto the cast iron and causing its carbon content to
drop. Th is process relies on another ancient Chinese inven-
tion, the double-action piston bellows, which forces air con-
tinuously into a forge or oven. Chinese inventors also came
up with gimbals—small iron rings that support an object
and allow that object to remain upright no matter how the
rings around it are turned. Th e gimbal became an important
component of marine compasses, which must function ac-
curately aboard ships in constant motion, and the gyroscope,
which was invented by the second century b.c.e. Th e Chinese
also invented, in the ancient period, umbrellas, stirrups, por-
celain, hot-air balloons, iron plows, kites, and paper. Chain
pumps, which allow users to raise water from a canal or ditch
into a fi eld of crops, are still in use in rural China. Th e south-
pointing carriage was used for navigation on land. Th e device
supported the fi gure of a man, pointing toward the horizon;
no matter which way the carriage was turned, the fi gure al-
ways pointed south. A complex series of gears governed the
transfer of motion from the wheels to the fi gure.
One of the marvels of early Chinese science and engi-
neering was the curious object known as the spouting bowl.
Th is large, precisely cast bronze bowl was fi lled with water.
When the bowl was carefully rubbed at the handles, the wa-
ter within the bowl began to spout and the entire bowl be-
gan to hum. Th e steady rubbing created a certain wavelength
and frequency in the water’s motion that caused a standing
wave—one that moves up and down, not sideways.
One of the most important scientifi c quests of ancient
China was the search for an elixir of life. Chinese alchemists
sought to create gold and silver from baser elements and ex-
perimented with the properties of semiprecious stones such
as jade. One could be made immortal, it was believed, if one
ingested an eternal substance, such as gold, which does not
rust or burn.
Chinese alchemists undertook long and complex experi-
ments, always basing their work on the fi ve elements and the
concept of yin and yang. Th ey heated and mixed chemicals
derived from rocks, soil, and earth, as well as bones, teeth,
and hair. Th ey dissolved them in water, vinegar, mercury, and
saltpeter. Th ey studied the changes in the color and appear-
ance of the elements, noting that diff erent metals have dif-
ferent melting points and give off diff erent colors when put
in the fi re. Alchemists also studied the eff ect of these sub-
stances on the body when applied to the skin or when taken
in through drinking or eating them. Early chemical experi-
mentation was held to be a great secret in ancient China and
forbidden to common workers and peasants. Chemists, as-
tronomers, geologists, and other scientists worked diligently
for the emperor and were kept within the palace quarters and
the imperial capital, where they were closely watched.
One of the most important scientists of ancient China
was Zhang Heng, a scholar of the Han dynasty, who was
born in 78 c.e. He served the dynasty as imperial historianscience: Asia and the Pacific 9330895-1194_Soc&Culturev4(s-z).i933 933 10/10/07 2:30:29 PM