Friends who like to study horoscopes must have heard of the astrological chart, and they will more or less understand their love career horoscopes through the astrological chart and so on.
In fact, in astronomy, the astrolabe is used to observe the sky and the earth. Today we will talk to you about this instrument.
As early as the ancient Greek period, astronomers invented a small astronomical instrument, the astrolabe.
It is generally in the shape of a metal disc and can be used handheld. Its functions include measuring the height of celestial bodies, identifying stars or planets, determining their latitude based on local time, making triangulations, and more. It can be said that the astrolabe is a very wide range of instruments and played an important role in ancient astronomical measurements.
It should be noted that the ancient astrolabe can also be predicted in addition to astrology.
Astrolabe of the ancient Greek period
The first known record of the astrolabe was made by alexander's scholar Theon in the 4th century AD, who made a more detailed account in his book The Astrological Disk.
But Theon was not the first person to shoot the star disk, according to Theon's contemporary Sinisius, hundreds of years ago the astronomer Hipparchus used an instrument for measuring celestial bodies, which had only a disk and a voyeur, which should be the original appearance of the astrolabe.
Ptolemy also mentioned that he used an instrument similar to Hipparchus to observe celestial bodies. According to this information, it is currently believed that the earliest astrolabe was invented by Hipparchus in the 2nd century BC.
An ancient book introducing the astrolabe Image source: wiki
The development of the astrolabe in the Arab world
Although the astrolabe originated in ancient Greece, it was further developed after it was introduced to the Arab world in the Middle Ages. The eighth-century mathematician Muhammad Fazari was the first person in the Arab world to build an astrolabe, and soon the Arabs fell in love with the small and lightweight instrument.
Due to the requirements of the doctrine, the Arabs had to perform the worship ceremony on time and accurately grasp the time of the sun and moon, and also to know the direction of the religious shrine, so the appearance of the astrolabe just met their needs. In order to be able to get better results, the Arabs modified the astrolabe, adding some new structures and functions.
Among them, the most important change is the introduction of an angle scale and the addition of a horizon circle representing the squared position of the ground. In this way, in addition to calculating the time when the sun and stars rise, it is also possible to determine the specific time and direction of worship, which is a function that is very important for Muslims.
In 1282, an astrolabe with Arabic was made
Later, the astrolabe developed in many different forms in the Arab world, such as a spherical astrolabe recorded at the end of the 9th century, which was a combination of an astrolabe and an armillary sphere; in the 12th century, a linear astrolabe was invented, which was shaped as a wooden rod with a scale but no scope, equipped with plumb lines and hands; in 1235, Abi Bakr of Isfahan invented a mechanical gear astrolabe.
The Arabs developed the style and function of the astrolabe to almost the extreme.
Structure of the astrolabe
The main body of the astrolabe is a disk, usually made of brass, with the middle part recessed to form a cavity, marked with a scale on the circumference of the disc, indicating the horizon circle, and the bearing and angle values can be read.
The back of the disc is often engraved with the scales required for various applications, including time conversion curves, calendars that convert months to the position of the sun on the ecliptic, triangulation scales, and more.
Disassembled astrolabe Image source: wiki
In the recessed part of the disk, it will generally be equipped with several thin disks with different scales, on which will be engraved circles representing the ecliptic belt, the names of constellations, some of the brightest stars, and so on. These thin discs can be replaced according to different needs.
On the outside of the thin disc is a hollow disc with the range of the celestial sphere and the range of the visible sky, usually with scales and decorative figures.
On the outermost side is a ruler with a scale, also called a calibrator, with small holes at both ends to peek into celestial bodies for measurements of height and orientation. The calibrator can be mounted on the outermost side or on the back.
These parts are connected together by a central axis, forming a complete astrolabe.
Disassembled astrolabe Image source: wiki
How to use the astrolabe
The astrolabe can be installed according to different needs when the astrolabe is used, and the illuminator can also be installed in front or behind, and then the illuminator is rotated to obtain the desired result according to the reading. Below we give two practical examples.
Example 1, measure the height of a celestial body: the astrolabe is placed vertically, watch whether the horizontal and vertical scales on the astrolabe are consistent with the vertical state, and then find the measured object through the small hole on the illuminator, so that the celestial body is seen through the small holes at both ends of the illuminator, and then read the scale value pointed by both ends of the illuminator to know the height of the celestial body.
Measuring building heights with astrolabes source wikis
Example 2, confirm the zodiacal constellation where the Sun is located: when the Sun rises, the position of the Sun is observed through a small hole in the illuminator, and the trajectory of the Sun in the sky is obtained through continuous observation. Then turn the thin disk with the ecliptic band so that the above line coincides with the observed sun trajectory, and the constellation pattern corresponding to the line is the zodiac sign where the sun is located.
The above is just a relatively simple example of a astrolabe application, through a series of observations and calculations, you can get more information. Of course, the accuracy of this observation cannot be compared with modern astronomical instruments, but in ancient society, it can fully meet the needs of people at that time.
In addition to applications in the field of astronomy, astrolabes also play an important role in religious and everyday applications. Before the invention of the sextant, the astrolabe was probably the most widely used small scientific instrument in ancient times.
There are many more instruments related to astronomy, and I am interested in the follow-up and interpretation with you.
Audit expert: Lu Yang Xiaoyi, Ph.D. in planetary physics
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Tadpole stave original article, reprinted indicating the source
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