Three hundred years ago, a heated argument took place in the courtroom of Mughal Emperor Muhammad Shah. The Emperor had wanted to know if the planets were in a favourable position for him to undertake an important journey. But the dozen or so astronomers came up with different calculations and were unable to agree on an “auspicious” date. The Emperor looked at them in exasperation. His kingdom was in danger of being attacked by the Marathas from the south, and the Persians from the north. He really needed to set off at once to secure the support of as many neighbouring Hindu kingdoms as he could. If only his astronomers would come to a conclusion!
Quietly watching this commotion was Maharaja Sawai Jai Singh. He was the Rajput king of Amber, a close ally of the Mughals. His was a rare talent, for apart from being a shrewd king, he was well versed in mathematics, architecture and astronomy. Brewing in his head at the moment was an ambitious plan. The Emperor caught the look of intense concentration on Jai Singh’s face, and knew that his troubles were about to end. For this man was gifted with extraordinary intellect.
“What do you have in mind, Sawai Jai Singh?” asked the Emperor.
“Simply to build the largest astronomical observatory in the world.”
Observe and learn
In the period between the years 1724 and 1734, a truly international collaboration of mathematicians resulted in the rise of the Jantar Mantar observatories at Delhi and Jaipur. Sawai Jai Singh consulted Islamic astronomers and studied their calendars. He read about ancient astronomical observatories in Babylon and China.
He spoke to European Jesuit missionaries, asking them all about the latest development in Greek astronomy. He was a keen student of the works of ancient Indian mathematicians, as well as Ptomely and Euclid. He himself was an architect, trained in traditional Indian methods of precise geometric construction. Pooling all this knowledge together, he came up with a number of huge observatories that were not only massive in scale, but also more accurate than any instrument in use then. Today, they are a standing example of using geometric designs ingeniously to make astronomical observations. One of the most striking structures at Jaipur’s Jantar Mantar is the ‘Samrat Yantra’. This is the world’s largest sundial. A sundial has two parts — a gnomon (pronounced no-mon) and a scale. A gnomon is a long triangular structure. The scale is drawn in a circle at the base of the gnomon. As the day progresses, the gnomon’s shadow moves along the scale. The gnomon at Jaipur is 73 feet tall (about as much as a seven-storey building). There are two arc shaped ramps on either side that reach up to 45 feet. You can climb up these ramps to watch the shadow of the gnomon fall on the scale below. The smallest division of the scale corresponds to two seconds. This means that you can read the time off this dial to an accuracy of two seconds. Before this mammoth structure was built, astronomers had only small brass instruments that could not be calibrated to such precision. Sawai Jai Singh simply increased the size of this instrument by more than a hundred times, and achieved a degree of accuracy never before possible.
And so the royal astronomers finally reached a consensus on which planetary position was most favourable for their Emperor. It is another matter however, that in 1739, Muhammad Shah was defeated by the Persian Emperor Nadir Shah.
Well at least, mathematics marched on, undefeated!
Where is the sun?
There are a number of such fascinating structures, but one of the most elaborate is the ‘Jai Prakash Yantra’. This was built to find the position of the sun in relation to other stars and planets. Because the sun is so bright, none of the other heavenly bodies are visible to us in the day time. So how do we know where the sun is? By using the Jay Prakash Yantra. There are two huge bowls, sunk partly into the ground. The diameter of the bowls at Jaipur is 17.5 feet (a little longer than the average sedan). Engraved in each of these bowls is the map of the heavens — different maps for different seasons. In addition to that, he divided the map into segments separated by steps. Going up and down these steps is like taking a walk across the sky. A crosswire stretched across the rim of the bowl casts shadow over the map on a clear day, showing the co-ordinates of the sun.
