Jaipur’s Jantar Mantar: Legacy of an Astronomer-King

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    Culturally vibrant and terribly atmospheric, Rajasthan’s capital city, Jaipur, is a heady mix of past and present. Among the city’s many palaces, architectural wonders, and chaotic and colourful bazaars is the Jaipur Observatory or Jantar Mantar.

    Located near the City Palace and Hawa Mahal in the Old City, the observatory is a sprawling property where discs, dials, arcs, arches, orbs, pillars and tablets are a testament to the astronomer-king who charted the heavens to indulge his passion for astronomy and to enhance his diplomatic and political career as well.

    The Jaipur Observatory or ‘Jantar Mantar’, built by Maharaja Sawai Jai Singh II (r. 1686 – 1743) between 1724 and 1727, is a collection of 20 large instruments that calculate the position and movement of celestial bodies with the naked eye. These instruments are not only impressive for their scale and size but also because they are made of stone and masonry. Amazingly, these monumental instruments were state-of-the-art and were even more accurate than their contemporary, compact brass counterparts being used in other parts of the world.

    Why did Jai Singh II send his men far and wide to gather knowledge about the frontiers of astronomy? And why did he build, not just the observatory in Jaipur, but four other observatories, one each in Delhi, Varanasi, Mathura and Ujjain?

    Who was this Astronomer-King?

    Jai Singh was born on 3rd November 1688, in Amber, capital of the Kachwaha Rajputs located on the outskirts of the city of Jaipur. He was born into a royal Rajput family that ruled a regional kingdom with diminishing power under Mughal rule. The era in which he was born and was educated was instrumental in his keen interest in astronomy.

    His father, Bishan Singh, the regional ruler between 1689 and 1700, carried forward the royal legacy of education for his two sons. He enrolled them at a Sanskrit college in Varanasi, which is where Jai Singh mastered Hindi, Sanskrit, Persian, Mathematics and Martial Arts.

    Jai Singh was inclined towards mathematics and astronomy from a very young age. Apparently, he had made copies of two astronomy manuscripts at the age of 13 and these are still preserved in the City Palace museum in Jaipur.

    Although he ascended to the throne at the age of 11 years, after his father’s untimely death in 1699, the young royal never gave up his academic pursuits. He had inherited great diplomacy skills and wit, which had impressed Aurangzeb so much that the Emperor bestowed on him the title ‘Sawai’, which literally meant ‘one and a quarter times greater than one’ (implying he was superior to his predecessors and contemporaries). Later, he was bestowed the titles of Saramad-i-Rajaha-i-Hind, Raj Rajeshwar, Shri Shantanu ji and Maharaja Sawai by Emperor Muhammed Shah.

    Jai Singh’s rule coincided with the decline of Mughal power after the death of Aurangzeb. Despite the turmoil and conflict of these times, he managed to expand and consolidate his kingdom and gained much respect. As the boundaries of his kingdom expanded, Jai Singh decided to build a new, planned, fortified city and he named it after himself – ‘Jaipur’. While construction of the new city began in 1725, Jaipur replaced Amber as the capital in 1733.

    This was a grand city, planned to the very last detail. It was built to incorporate aspects of the ancient architectural treatise Shilpa Shastra, the best of European town planning and Jai Singh’s own ideas. This plan was entrusted to ace architects from different eras – Vidyadhar Bhattacharya of Bengal and later Sir Samuel Winston Jacob, British Army Officer and an architect-engineer.

    The biographical account of Jai Singh II on the British Museum website states: “Jaipur, which was built on the grid system with nine rectangular zones corresponding to the nine divisions of the universe and had different zones allotted to different professions, boasted 119-feet-wide main streets that were perpendicularly intersected by 60-feet-wide auxiliary streets, which were further honeycombed by 30-feet-wide lanes and 15-feet-wide by-lanes. Beautiful, harmonized buildings and shady trees lined the streets, and the city was well-provided with water conduits and wells. The European travellers of the time, like the Frenchman Louis Rousselet, and the English bishop, Heber, were greatly impressed by Jai Singh's unparalleled excellence in city-planning.”

    The Maharaja meets his Mentor

    During his travels to the Deccan to meet Aurangzeb, Jai Singh II befriended Jagannatha, who had a keen mastery over astronomy and mathematics. He soon became the king’s mentor and chief advisor in matters concerning astronomy. Jagannatha also served in the royal court and significantly influenced the design of the Jaipur Observatory.

    Both men often discussed traditional Indian astronomy treatises and Islamic astronomy treatises, which were the main guiding principles for the calendars that decided auspicious times for any rituals or for embarking on new conquests.

    In due course, Jai Sigh discovered many discrepancies in the tables and the measurement of time and position of the planets, which led him to realise the need for accurate astronomical instruments. The Indian astronomical treatises, right from the Vedic era, siddhantas by Aryabhata and Brahmagupta mentioned observational instruments but they never disclosed their exact design. Meanwhile, Islamic astronomy mentioned the astrolabe.

    While Hindu astronomers mainly mentioned instruments to measure time rather than the coordinated systems of stars and planets, like water clocks and sundials, Islamic astronomy had compiled numerical astronomical tables called ‘Zijes’, which included latitudes, longitudes, trigonometric functions and elements of spherical astronomy. All these were derived from the Ptolemic model of the solar system.

    Islamic astronomers had compiled more than 200 different types of Zijes between the 8th and 15th century CE. The most famous Zijes were compiled in India – Zij-i-Muhammad Shahi – based on observations made at Jantar Mantar observatories (it is possible that Jai Singh had honoured Emperor Muhammad Shah for his support and repeal of unjust taxes). The last known Zij, known as Zij-i-Bahadurkhani, was compiled by Indian astronomer Ghulam Hussain Jaunpuri and it incorporated the heliocentric system.

    These constant modifications and corrections indicate that there were significant discrepancies in the observed and mathematical tables, and attempts were constantly being made to correct them. Hence, positional astronomical instruments played a key role in the continued study of astronomy across the globe and the Jantar Mantar Observatories of Jai Singh are a testament to that era.

    Cutting-Edge Innovations

    The most interesting aspect of the instruments at Jai Singh’s Jantar Mantar Observatories is that they are calibrated for multiple coordinate systems. With Jai Prakash (an instrument that is supposed to mirror the heavens), for a single celestial object, one can indicate its position with respect to the azimuthal and equatorial coordinate system. The same is true of the instruments that measure time. The smallest division of the giant Samrat Yantra – the giant sundial – corresponds to two seconds, so one can experience the motion of the earth as the shadow shifts. The various large instruments meant to measure the spatial coordinates of celestial objects with respect to the horizon at a given time also enhance this experiential learning!

    This makes these observatories relevant even today to study the basic principles of Positional Astronomy. Dr Nandivada Ratnashree, director of the Nehru Planetarium in Delhi, uses them to teach basic astronomy lessons. Often students are encouraged to visit these observatories and make measurements or observe the path of the sun and planets across the sky.

    Some historians believe that the giant instruments at the five observatories be built were meant as a show of power and wealth by Sawai Jai Singh II. Even if that were true, the fact that he invested space, money and manpower to build these architectural wonders to study basic astronomy cannot be refuted. Also, the intellectual and mathematical pursuit of astronomy has never been glorified by any other king in Indian history.

    Most importantly, these huge instruments made of stone as opposed to small brass instruments (vulnerable to shaking, temperature changes and inaccuracies), combined the principles of Indian, Islamic and western astronomy to attain their unprecedented accuracy. Portuguese Jesuits who had arrived in India by then and were based in Jaipur helped Jai Singh plan an expedition of his court astronomers to Portugal to understand the observation techniques and tabulations that were being used in Europe.

    Jai Singh was intrigued by the discrepancies and errors in the astronomical tables of La Hire (Layyer), which they had brought back. He corresponded with and invited French Jesuit astronomer Claude Boudier, who was based in Chandernagore (in Bengal), for consultation. Although Jai Singh did not use these tables, as they were based strictly on the Copernican system, Boudier went on to assist the Maharaja in setting up telescopes in Jaipur.

    Thus, Jai Singh can be counted as one of the most pioneering pre-colonial astronomers who made serious attempts to understand European science and astronomy, which later thrived in India. India has gone on to contribute greatly to the world of science thanks to this legacy of the open-minded pursuit of knowledge.

    The Instruments

    Following are the basic instruments at Jaipur’s Jantar Mantar:

    Samrat Yantra: This is the largest sundial in the world. Shaped in the form of a right-angle triangle with a hypotenuse (also called a ‘gnomon’), it rises 73 feet above the ground. Its primary objective is to indicate solar time. The gnomon is pointed towards the celestial pole and is supported by an arc that rises 45 feet. The shadow of the gnomon throughout the day sweeps through the calibrated quadrant from one end to the other. The time of day is indicated by the edge of the shadow on the quadrant scale.

    The instrument has a sighting device, which is designed to be versatile enough to study stars at night as well. One can also study the sun’s declination and the right ascension of any celestial object. A secondary instrument, called Shasthansa Yantra, which uses a pinhole camera mechanism, has been built within the towers that support the quadrant scales. It measures the zenith distance, declination and diameter of the sun.

    Jai Prakash: This is the most intriguing instrument, whose working concept dates to the Greco-Babylonian era (early 300 BCE) when first the hemispherical sun dial was made by astronomer Berosus. It is one of the most versatile and complex instruments that give the coordinates of the celestial objects in multiple systems – the Azimuthal-altitude system and the Equatorial coordinate system. This enables easy conversion and perception of the popular celestial coordinate system.

    The instrument itself is a big bowl that partially rises above and below the ground. The Jaipur Jai Prakash instrument’s diameter of the rim is 17.5 feet, whereas it is bigger – 27 feet – in Delhi. The bowls are inverted celestial spheres – one for the day and the other aided with a sighting device for night observations. They have the respective coordinates inscribed on them to enable observing any celestial object and measuring their coordinates in any of the systems. The multimedia website in collaboration with an outreach program of Cornell University in the United States is enabling a better understanding of these instruments through virtual simulation.

    Ram Yantra: This is a cylindrical structure instrument, built in pairs, to measure the altitude and azimuth of celestial objects. It was a first of its kind instrument in the history of Indian and Islamic schools of astronomy for measuring the altitude and azimuth with accuracy.

    Kapala Yantras: They were built before the construction of the Jai Prakash on the same principle but these are more demonstrative instruments to indicate the transformation of one coordinate system to another. They are not for active celestial observations. These could have been prototypes for the Jai Prakash.

    Rasivalya Yantras: There are 12 of these – each one referring to the Zodiacal constellations. They measure the latitude and longitude of a celestial object at the exact moment when that constellation crosses the meridian.

    Legacy & Scope

    As the design and scope of the instruments indicate, Jai Singh did not build these observatories as architectural marvels to merely enhance his reputation. He was serious about accurate and precise celestial observations in order to correct the discrepancies in the existing astronomical observation tables. The astronomical charts and tables that came out of these projects have led to almanacs that are still in use in Rajasthan.

    Apart from the astronomical charts, Jai Singh has created an entire open-field classroom to learn physics, astronomy and mathematics. His observatories are mathematical spaces with huge instruments that have inscribed scales in multiple coordinate systems and these are great spaces for learning time measurement, coordinate geometry, coordinate transformation, astronomical observations and much more.

    As mentioned earlier, Dr Nandivada Rathnashree, director of the Nehru Planetarium in Delhi, often conducts classes and observations of celestial events at Jai Singh’s Delhi Observatory. These can be replicated at the other observatories by science teachers and amateur astronomy enthusiasts so that instruments are well maintained and are in use.

    Of the five observatories built by the Maharaja, only four exist today. While the one at Mathura was dismantled in the 19th century, the observatories at Jaipur and Ujjain have been considerably restored.

    India should be proud to own a scientific and mathematical heritage like this, built in stone and mortar by a regional king who had a passion for Positional Astronomy based purely on scientific observations, mathematical calculations and evidence. Unfortunately, not much has been done to showcase and promote this legacy. Although these observatories are under the Archaeological Survey of India, there are no scientifically trained guides to explain the working and scope of these instruments and bring them to life for the public. Until such an attempt is made, visitors will have to figure out this monumental legacy of a Rajput king for themselves.


    Madhuri Katti is a Kolkata based physics teacher, heritage enthusiast and an aspiring writer.

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