Jantar Mantar Observatory PDF Print E-mail
Written by Yogesh Soman   
Saturday, 25 March 2006 23:46
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In early eighteenth century, a supernova, known by the name Sawai [[Jai Singh II]], exploded on the horizon of Indian Astronomy. During the brief period of his life, he tried to arouse Indian Astronomy which had been in a deep slumber for almost five centuries. He tried to give it a new life by bringing in new ideas from west. A chain of magnificent observatories known today as 'Jantar Mantar' (also known as [[Yantra Mandir]]) arose due to his efforts.

Here we are going to learn a little about these observatories and what sort of observations can be carried out from them. But before we take a tour of the Jantar Mantar itself, let us try to know a little about Sawai Jai Singh and the politico-historical situation prevalent in the early years of the eighteenth century.

Sawai Jai Singh and his times

Sawai Jai Singh, the statesman astronomer of India, was born to a royal family on November 3, 1688 in the town of Amber in the state of Rajasthan, India. One of Jai Singh's ancestors, Bharamala or Biharimala (d. 1573), recognised the ascendency of Mughal power and accepted the suzerainty of the emperor Akber in 1562. This made the house of Amber the most influential of all the Rajput houses serving the Mughals. Bharamala's descendents, Mana Singh (1543-1614) and Mirza Raja Jai Singh (1611-1667, great grand father of Sawai Jai Singh), were highly regarded nobles at the Mughal court and were entrusted with important missions.

Jai Singh displayed interest in mathematics at an early age. He had two manuscripts on astronomy copied for him when he was only thirteen. However, his formal education was cut short at the age of eleven when his father died, and he had to take charge of the administration. He ascended the throne of Amber on January 25, 1700. However, he continued his studies along with the discharge of his princely duties and soon acquired mastery over the subjects of astronomy and mathematics.

During the next ten of fifteen years of troubled and uncertain times in the history of India and Delhi, Jai Singh by clever politics became the largest single land owner amongst the kings of Rajasthan. It is said that at the peak of his time, he owned all the land between Delhi and the shores of Gujarat at Surat.

With great wealth and resources available to him as a powerful ruler, Jai Singh embarked upon an ambitious program of reviving astronomy in India. To this effect, he designed instruments, built observatories, compiled an excellent library, assembled competent astronomers of different scientific backgrounds, and sent a fact-finding scientific mission to Europe. His scientific career lasted more than 20 years until his death in 1743 at age 54.

Decision to build Observatories

Sawai Jai Singh had noted that the astronomical calculations based on the existing planetary tables did not always agree with observations. The problem was especially serious with the appearance of the new moon - the computations of which did not agree with the observations.

Discrepancies were also to be found in the time of rising and setting of the planets, and the seasons of eclipses of the sun and moon. These times were important both from purely astronomical point of view as well as with the important decisions relating to governance and other religious activities. In order to remove these errors new sets of observations were necessary. Thus with the view of setting the astronomical tables straight, Sawai Jai Singh approached the then mughal emperor Muhammad Shah with the request for permission to build the observatories.

He built five observatories in total, which are known today as 'Jantar Mantar'. They were at Jaipur, Delhi, Mathura, Ujjain and Varanasi and were completed between 1724 and 1735. The one at Jaipur was the largest with the maximum number of instruments. The observatory at Mathura vanished sometime around 1850. Those at Varanasi and Ujjain exist in various degrees of preservation.

The idea behind building a number of observatories at different locations in the northern India was to make the same observations from different places and thus reduce the errors introduced due to the limits of human vision.

While building the observatories Jai Singh had the choice of constructing either metal instruments or masonry instruments. The metal instruments, constructed according to the texts of the Islamic school of astronomy, did not measure up to Jai Singh's expectations. He discarded them in favour of the instruments of stone and masonry that he himself designed. He tried to achieve the desired precision through their large size, and steadiness from the relative inflexibility of their structures. A French Jesuit, du Bois, writes that Jai Singh prepared wax models of these instruments with his own hands.

Before constructing their masonry instruments, Jai Singh and his associates selected a suitable ground first and leveled it with water standing in masonry channels built just for this purpose. Such masonry channels may still be seen at Jaipur and Ujjain. Next, north-south and east-west directions were marked on the ground, the procedure for which had been known for a long time and described in standard texts such as the Suryasiddhanta.

Just as in any other observatory of medieval times, Jai Singh's observatories primarily housed time-measuring and angle measuring devices. Jai Singh graduated his time measuring devices according to the dexagesimal scheme in which a 24-hour day is divided into 60 parts of ghatikas, and the ghatikas are in turn divided into 60 subparts known as palas. For measuing angles, he divided a circle into four quadrants of 15 main divisions each. He partitioned the main divisions further into six subdivisions of one amsa or one degree each. He divided the degree-divisions, as the scale permitted, into minutes or kalas. Sixty kalas equaled one amsa or degree. Any deviation from this division-scheme seen presently at his observatories is purely a modern adaptation. It has nothing to do with Jai Singh. The scale markings on Jai Singh's time-measuring instruments had zeros on the meridian line, and 15-ghatika marks along the east-west line. These instruments thus measured time from midday or midnight. The angle-measuring instruments had their zeros on the east-west line.

Last Updated on Thursday, 30 March 2006 23:46