Jantar Mantar

• 1. Introduction

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  Jantar Mantar names a collection of stone-built astronomical instruments designed to be used with the naked eye. Five of these observatories were built across India between 1724 and 1735, all at the command of a single man: Raja Jai Singh II, whose appetite for mathematics, architecture, and astronomy drove one of the most ambitious scientific construction projects of the early eighteenth century. What could stone instruments, fixed in place and open to the sky, tell an observer about the movement of the sun, moon, and planets? And how did a name that sounds like an incantation come to describe a series of precision measuring machines? Those are the threads this documentary follows.

• 2. Jai Singh's Vision

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  Maharaja Jai Singh II of Jaipur ordered observatories raised in five cities: New Delhi, Jaipur, Ujjain, Mathura, and Varanasi. Construction ran from 1724 to 1735. The practical goal driving this enterprise was the compilation of astronomical tables. Jai Singh wanted instruments capable of predicting the times and movements of the sun, the moon, and the planets with enough reliability to be useful. Each observatory contained a suite of devices: the Samrat Yantra, the Jai Prakash Yantra, the Disha Yantra, the Rama Yantra, the Chakra Yantra, the Rashiwalya Yantra, the Dingash Yantra, and the Utaansh Yantra. Not all five sites survived intact. The observatory at Mathura, along with the fort that once protected it, was destroyed before 1857.

• 3. The World's Largest Stone Sundial

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  At Jaipur, the centrepiece of the assembly is the Samrat Yantra, recognized as the world's largest stone sundial. Its core is a gigantic triangular gnomon whose hypotenuse runs parallel to the Earth's axis. On each side of that gnomon sits a quadrant of a circle, oriented parallel to the plane of the equator. A skilled observer working with this instrument can determine the time of day and the declination of the sun and other heavenly bodies to an accuracy of about 20 seconds. That precision, achieved entirely in stone and without any mechanical moving parts, is what sets the Jaipur site apart from every other observatory in the complex. The Jaipur Jantar Mantar has since been designated a UNESCO World Heritage Site.

• 4. A Name Older Than Expected

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  The phrase "Jantar Mantar" appears in an account written in 1803, making the name at least 200 years old. Yet the official archives of Jaipur State from 1735 and from 1737 to 1738 do not use it. Those records favour a different spelling: Jantra. The spoken language gradually wore "Jantra" down to "Jantar." The word itself traces back to yantra, the Sanskrit term for instrument. The second half of the name, Mantar, comes from mantrana, a word meaning to consult or to calculate. So the phrase that today sounds almost like a magic formula is, at its root, a plain description: instruments for calculation.