Jantar Mantar in the heart of Delhi, which has served as a dynamic venue for agitations—protests, rallies and campaigns on social and political issues—is once again in the news, making global headlines. Independent of what each of our opinions is on the agitation or on the government's response, many of us don’t seem to know much about the significance of this historic site of agitation and what it stands for.

In 1724, Maharaja Sawai Jai Singh II built Jantar Mantar, the Delhi astronomical observatory, and he went on to build others at Jaipur, Ujjain, Mathura and Varanasi. These large observatories, meant for naked-eye observations, were built to prepare astronomical tables and improve the accuracy of astronomical observations—predicting eclipses, measuring time and tracking the movements of the Sun, Moon and stars. Jai Singh built these large instruments to achieve higher accuracy.

The instruments at Delhi's Jantar Mantar include a variety of ingeniously constructed positional astronomy instruments—Samrat Yantra, Ram Yantra, Jaiprakash Yantra and Misra Yantra. Naked-eye observations from these observatories resulted in a significant set of star tables, the Zij-i Muhammad Shahi. The significance of these observatories led to the Jaipur observatory being recognised as a UNESCO World Heritage Site in 2010.

Teaching Astronomy Through Ancient Instruments

My late friend Dr Rathnasree, director of the Nehru Planetarium in Delhi, used these observatories to teach positional astronomy to school students. Moving through these instruments gave students a feel for walking........

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