Inspired by the 15th-century Afghani ruler Ulughbek's observatory at Samarkand, the great Indian astronomer-king Maharaja Jai Singh II of Jaipur built these five astronomical observatories during the early 18th century.

Like many amateur astronomer, Jai Singh had an insatiable curiosity about the heavens. Observing a six-minute difference between the predicted and the observed start of a lunar eclipse made him wonder what might have gone wrong. While Ulughbek had compiled a set of astronomical tables used for eclipse prediction, they had become obsolete by Jai Singh's time.

To correct these tables, he set out to build a large observatory in Delhi. He made careful observations from the Jantar Mantar for seven long years to prepare a new and accurate star catalogue. The updated catalogue of 1018 stars was called Zij Muhammad Shahi after the Mughal ruler Muhammad Shah. The king also constructed similar observatories in the cities of Jaipur, Ujjain, Benares and Mathura.

A Structural Approach To Astronomy...

The Jantar Mantar bears an array of masonry instruments that were used to predict time, measure the position of a celestial body and the latitude. Instruments at Delhi include the Brihat Samrat Yantra, the Rama Yantra and the Jai Prakash Yantra. The largest of these is the Brihat Samrat Yantra, a massive sundial that that dominates the observatory while giving the accurate local time.

The Rama and Jai Prakash Yantras were designed by Jai Singh to measure precise positions of celestial bodies in the night sky. The Rama Yantra has a pillar in the center like ancient shadow clocks. When the sun is high in the sky, the pillar casts a shadow either on the vertical well surrounding the pillar or the raised floor segments radiating from the pillar. These segments and the walls have fine graduations. Positions of the sun, moon, planets and stars can be measured using this instrument. Most were constructed in pairs to correct for and errors in the individual instruments.

...For More Pertinent -- and Permanent -- Results

So why did Jai Singh build instruments of brick and concrete when his contemporaries in Europe like Galileo used telescopes? Jai Singh himself answered this question in Zij Muhammad Shahi:

"It should be maintained that these instruments (of the Europeans) were not large and, therefore, the calculation and observations were somewhat inaccurate, since the atmospheric conditions had a strong influence on those instruments; we explained that the inadequate accuracy of the observatories and measurements by Hipparchus, Ptolemy and others indicated this."

Jai Singh had sent several skilled people to Europe to collect astronomy texts and instruments. "People from his court went to Spain and Portugal for learning western astronomy. They brought back with then many instruments, including a telescope," says doctor N. Rathnasree Dasgupta, director of the Nehru Planetarium in New Delhi.

"But one must realize that Spain and Portugal were good for navigational astronomy and the real science was done in Rome by Galileo and in England," she added.

But historians believe that the reason Jai Singh built these large fixed instruments without any optical devices had more to do with Hindu philosophy than astronomy. Through these astronomical structures, which were visible from great distances, Jai Singh was proclaiming his worldly power.

Immortality may have been an added bonus. The astronomer-king stands at the crossroads of astronomy in India as a link between the ancient cosmic world and the new scientific order. More than 250 years after the publishing his Zij Muhammad Shahi, Jai Singh's tables continue to be in use even today.

"The traditional Rajasthan tribal Pachang (Hindu calendar) is based on Jai Singh's data. Apart from this, he also wanted to popularize astronomy among the masses," Dr. Rathnashree observed.