Obervation Method of Eclipse in Ancient Chinese Astronomy

Eclipse is one of the important astronomical events humans can perceive by eyes, so humans pay more attention to it in ancient times. There are quantities of records of eclipse observation. In about 20 centuries BC, the earliest record of eclipse in the world is found in a Chinese chronology. It is estimated that there are about thousands of records of eclipse in Chinese chronology (the most in the world).

In ancient times, the main method of observing eclipse is reflection from water basin, which is used in 1 century BC. In Song Dynasty, people began to use oil basin instead of water basin. And in Yuan Dynasty, GUO Shoujin did measurement of eclipse by means of image by ping hole. At the end of Ming Dynasty, Astronomer, XU Guangqi had begun to observe the eclipse by means of telescope.



Reflection of eclipse in ink water basin



Chinese Ancient Astronomer "GUO
Shoujing" in Yuan Dynnasty

The history of the mirror

The first mirrors used by people were most likely pools of dark, still water, or water collected in a primitive vessel of some sort. The earliest manufactured mirrors were pieces of polished stone such as obsidian, a naturally occurring volcanic glass. Examples of obsidian mirrors found in Anatolia (modern-day Turkey) have been dated to around 6000 BC. Polished stone mirrors from central and south America date from around 2000 BCE onwards. Mirrors of polished copper were crafted in Mesopotamia from 4000 BC, and in ancient Egypt from around 3000 BCE. In China, bronze mirrors were manufactured from around 2000 BC, some of the earliest bronze and copper examples being produced by theQijia culture. Mirrors made of other metal mixtures (alloys) such as copper and tin speculum metal may have also been produced in China and India. Mirrors of speculum metal or any precious metal were hard to produce and were only owned by the wealthy.

Metal-coated glass mirrors are said to have been invented in Sidon (modern-day Lebanon) in the first century AD, and glass mirrors backed with gold leaf are mentioned by the Roman author Pliny in his Natural History, written in about 77 AD. The Romans also developed a technique for creating crude mirrors by coating blown glass with molten lead.

Parabolic mirrors were described and studied in classical antiquity by the mathematician Diocles in his work On Burning Mirrors. Ptolemyconducted a number of experiments with curved polished iron mirrors, and discussed plane, convex spherical, and concave spherical mirrors in his Optics. Parabolic mirrors were also described by the physicist Ibn Sahl in the 10th century, and Ibn al-Haytham discussedconcave and convex mirrors in both cylindrical and spherical geometries, carried out a number of experiments with mirrors, and solved the problem of finding the point on a convex mirror at which a ray coming from one point is reflected to another point. By the 11th century, clear glass mirrors were being produced in Moorish Spain.

In China, people began making mirrors with the use of silver-mercury amalgams as early as 500 AD. Some time during the early Renaissance, European manufacturers perfected a superior method of coating glass with a tin-mercury amalgam. The exact date and location of the discovery is unknown, but in the 16th century, Venice, a city famed for its glass-making expertise, became a centre of mirror production using this new technique. Glass mirrors from this period were extremely expensive luxuries. The Saint-Gobain factory, founded by royal initiative in France, was an important manufacturer, and Bohemian and German glass, often rather cheaper, was also important.

The invention of the silvered-glass mirror is credited to German chemist Justus von Liebig in 1835. His process involved the deposition of a thin layer of metallic silver onto glass through the chemical reduction of silver nitrate. This silvering process was adapted for mass manufacturing and led to the greater availability of affordable mirrors. Nowadays, mirrors are often produced by the vacuum deposition of aluminium (or sometimes silver) directly onto the glass substrate.

Seated woman holding a mirror

Chronologies of Metal's History in Ancient China

PERIOD 1:

In the period of Xia, Shang and Zhou Dynasty, multitudes of bronze objects were produced. And the foundry technology of bronze had reached a high level with the development of “slave society”.

The types of bronze objects can be divided into 3 parts according to the usage: producing tools, weapons, vessels for ritual and household appliances.

"Bronze Plate"

PERIOD 2:

The foundry of iron dates back from the Period of Warring States, which is connected with the establishment of feudal society. There are 2 kinds of techniques of foundry: foundry of block iron and foundry of pig iron. All kinds of types, such as white pig iron and grey pig iron, are widely used.

And at the same time, the ironmaking furnace, fuels and blowing machine had also developed accordingly.

"Iron Arrow"

PERIOD 3:

With the development of feudal society, different kinds of technologies of steel foundry had been created by the people, such as:

1.       Steel is from the foundry of block iron that is filled with carbon – had been introduced into application before the Period of Warring States.

2.       Steel must be tempered for more than hundreds of times - started from the middle age of West Han Dynasty and developed from the early stage of East Han Dynasty.

3.       Steel should be fried when smelted so as to take off the carbon and oxygen in pig iron – maybe it appears between two Han Dynasties.

4.       Steel is from the iron casting that is filled with no carbon – developed from at least West Han Dynasty and was widely used in Han Wei Dynasty.

5.       Steel is from the mixture of foundry between wrought iron and pig iron – it’s a kind of important technology of steel foundry starting from North and South Dynasty.

"Steel Sword of Tang Dynasty"

PERIOD 4: 

The foundry of bronze had developed further on the basis of technologies in Shang and Zhou Dynasties. A new kind of way in copper foundry – putting iron into copper-bath was created.

Brass was created. Zinc was extracted from mineral successfully.

Gold and silver were only used as currency and made into delicate adornments in ancient times.

"Brass Bowel"

"Gold and Silver Accessories"