Celestial Globes
In the history of educational devices invented to disseminate learning about the position and movement of the heavenly bodies, a celestial globe, which is also known as an armillary sphere, an armilla, armil, or spherical astrolabe, is surely one of the earliest and most successful.
The name derives from the Latin word 'armilla', which means a circle or a bracelet. The first such celestial globe system was invented and constructed by Erastothenes in ancient Greece, more than two and a half centuries before the birth of Christ.
The system was one composed of intersecting rings of metal, concentrically arranged from smaller to larger, from inside to outside. These linked sets of concentric circles connected the two poles and represented the meridians, the equator, the parallels and the ecliptic. A ball fixed at the center normally represented the earth, in accordance with the geocentric model that was popular at that time. This model was based upon the belief that the earth was at the center of the universe, and all other heavenly bodies revolved around it. However, many centuries later, when Nicolaus Copernicus demonstrated the error of that model, the central ball was interpreted to represent the sun rather than the earth.
Celestial globes or armillary spheres were quite popular as educational devices in the ancient world, and even the great astronomer Ptolemy is believed to have used them. But then they fell into decline with the fall of the Roman empire and the coming of the dark ages of Europe.
They again revived during the late middle ages, and by the time of the European renaissance, they were an indispensable instrument for scientists, mathematicians and philosophers, who used it also as an observational device.
The famous Danish astronomer Tycho Brahe, who lived from the middle of the 16th century to the very beginning of the 16th, constructed several celestial globes. Many of them are still in existence, and are preserved in museums around the world. These were vastly superior to what the ancients used, because these had been embellished by the much more expanded and improved knowledge of heavenly bodies and their movements, based upon centuries of observation, calculation and deductive reasoning.
Celestial globes were so popular and respectable during the renaissance that they became symbolic of wisdom, knowledge and higher understanding. Many famous scientists and thinkers of the age had portraits done of themselves which showed them in a flattering pose, holding a celestial globe in their hand.
Scientific and technological advancement stands upon the shoulder of previous achievements. Among the early mechanical devices of European history which inspired and contributed to the later rapid mechanization of Western civilization, the celestial globe is one of the most important and fundamental.
But this is not to say that celestial globes were unique to Europe. In fact, several samples have been discovered by archaeologists in the Far East that rival the earliest Western models in antiquity. Two ancient Chinese astronomers, named Luo Xia Hong and Geng Shou Chang, living during the period of the West Han dynasty in the first century BC, are credited with the first celestial globes of the Asian continent. Samples of their work can still be seen preserved in museums. Not much later, another Chinese astronomer called Zhang Heng invented a large celestial globe the motion of whose circles were powered by the flow of water.
And in the East, too, new technology has been based upon old. Centuries after Zheng Heng's water-based celestial globe, a Chinese monk improved upon it by adding an escapement device to it. The resultant gizmo can be said to be the world's first mechanical clock driven by hydraulic power.
Featured
Soon to come!
