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Jantar Mantar in India. Source: Aliaksei / Adobe Stock.

Jantar Mantar – The Ancient Astronomical Observatories of India

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The Jantar Mantar refers to a group of five astronomical observatories built in India during the 18th century. The largest and best-known of these observatories is located in Jaipur, a city founded by and named after Jai Singh II. This ruler was extremely interested in astronomy and therefore had an observatory built in the city he founded.

The Jantar Mantar in Jaipur is such an amazing feat of human ingenuity that it was recognized as a UNESCO World Heritage Site in 2010. Each Jantar Mantar contains various astronomical instruments, one of the most notable being the sundial. In fact, the Jantar Mantar in Jaipur boasts having the largest stone sundial in the world.

Origin of the Jantar Mantar

The word ‘Jantar Mantar’ is derived from a combination of two Sanskrit words, ‘yantra’ and ‘mantra’, the former meaning ‘instruments’, while the latter means ‘to calculate’. Therefore, the Jantar Mantar quite literally means ‘instruments to calculate’.

Indeed, the instruments built at these observatories were meant to perform various types of astronomical calculations. While the sundial is the instrument most are familiar with, there were also other more complex instruments. Some of these instruments will be discussed later on.

As already mentioned, there were five Jantar Mantar built around India. Apart from Jaipur, smaller observatories were built in Delhi (specifically in the area that later became New Delhi), Ujjain, Varanasi, and Mathura. The earliest of these five Jantar Mantar was the one in Delhi, which was constructed in 1724, and the other four in the years that followed. The four subsequent Jantar Mantar were built in order to reaffirm the astronomical readings that were being recorded in Delhi.

Jantar Mantar in New Delhi, India. (A.winzer / CC BY-SA 3.0)

Jantar Mantar in New Delhi, India. (A.winzer / CC BY-SA 3.0)

One remarkable aspect of these observatories is that although some of the instruments, for instance, the sundial, are found in the different observatories, each Jantar Mantar is unique. None of the five Jantar Mantar are the same in terms of size, layout, and style. Today, all of the Jantar Mantar, apart from the one in Mathura, is still in existence and may be visited by the public.

The observatory in Mathura, incidentally, was demolished just before 1857, along with the fort that housed it. The Jantar Mantar were built on flat ground, free of trees, so that no shadow would obstruct the use of the instruments. The situation, however, has changed today.

At the Jantar Mantar in Delhi, for instance, accurate readings can no longer be made due to the tall buildings around the observatory. Nevertheless, some of the instruments are still being used to forecast weather and crop yields.

Jai Singh Builder of the Jantar Mantar

The construction of the Jantar Mantar was possible thanks to an extraordinary individual, Jai Singh II, the Hindu Rajput ruler of the Kingdom of Amber (known also as the Kingdom of Jaipur or Jaipur State). Jai Singh was born in 1688 in Amber, in what is today the state of Rajasthan. In 1699, Jai Singh’s father, Bishan Singh, died, and was succeeded by his 11 year-old son.

When Jai Singh succeeded his father, the Kingdom of Amber was a feudatory of the Mughal Empire, which was the dominant power in the Indian subcontinent at that time. Since 1658, the Mughal Empire was ruled by Aurangzeb, widely considered to be the empire’s last great ruler, though also notorious for his political and religious intolerance.

Aurangzeb pursued an expansionist policy and it was during his reign that the Mughal Empire reached its greatest extent. The predecessors of Jai Singh preferred dealing with the Mughals through diplomacy, rather than through force of arms, as their kingdom was situated not far from Delhi and Agra, the power centers of the Mughal Empire.

Therefore, when Jai Singh became the new ruler of Amber, he continued serving as a vassal of the Mughals. Nevertheless, he was a shrewd ruler and managed to gain the favor of Aurangzeb. Soon after his ascension, Jai Singh was ordered by Aurangzeb to serve in his military campaign against the Marathas in the Deccan.

Following his capture of the fort of Vishalgarh from the Marathas, Jai Singh was awarded the title ‘Sawai’, which means ‘one and a quarter’, which signifies that he was a quarter greater than his illustrious ancestor, Jai Singh I. In 1712, the title was officially recognized by an imperial edict, and in commemoration of this recognition, Jai Singh initiated the practice of flying two flags, one full and one quarter-sized. This practice, along with the title ‘Sawai’, was inherited by Jai Singh’s successors.

According to another story, it was Jai Singh’s wit that earned him the title ‘Sawai’. In this tale, Jai Singh was summoned by his overlord for contravening an agreement of not waging war against the Marathas. When the king arrived at Aurangzeb’s court, the emperor clasped his hands in greeting, while demanding an explanation for his actions.

Jai Singh built the Jantar Mantar – his greeting of the emperor earned him the title of ‘Sawai’. (Raghu-holkar / CC BY-SA 2.0)

Jai Singh built the Jantar Mantar – his greeting of the emperor earned him the title of ‘Sawai’. (Raghu-holkar / CC BY-SA 2.0)

Jai Singh, who was 15 at that time, replied that since Aurangzeb had extended his hand, it meant that the emperor would protect him and his kingdom. Aurangzeb was pleased with the reply and granted Jai Singh the title of ‘Sawai’.

After the death of Aurangzeb in 1707, the Mughal Empire went through a period of political instability, despite having an emperor, Bahadur Shah, on the throne. The intolerant policies of Aurangzeb resulted in various rebellions across the empire, while palace intrigues and political conspiracies were rife in the Mughal court. In 1719, for instance, there were four successive emperors on the Peacock Throne.

That year also saw some sense of stability returning to the empire, when Muhammad Shah became emperor in late September. Compared to the last few Mughal emperors, Muhammad Shah had a long reign, as he ruled the empire until 1748. In the meantime, Jai Singh, being an astute ruler, was able to maintain his political importance in the turbulent years following Aurangzeb’s death.

In addition, when Muhammad Shah came to power, Jai Singh became a favorite of the emperor, just as he had been during the time of Aurangzeb. It was thanks to Jai Singh’s instigation, for instance, that Muhammad Shah abolished the Jaziya tax that was imposed on the empire’s Hindu subjects.

Jai Singh was not only a capable ruler, but also expressed great interest in various areas of science, most notably in astronomy. It was Jai Singh who brought to the attention of Muhammad Shah that there were certain astronomical discrepancies that may have an effect on the timing of both Hindu and Muslim holy events. In addition, the king expressed his desire to rectify these errors.

The instruments of the Jantar Mantar were to correct the astronomical discrepancies and their effect on the timing of holy events. (Russ Bowling / CC BY-SA 2.0)

The instruments of the Jantar Mantar were to correct the astronomical discrepancies and their effect on the timing of holy events. (Russ Bowling / CC BY-SA 2.0)

Muhammad Shah, being a cultured man, and a great patron of the arts, supported Jai Singh’s endeavor. Therefore, having received the emperor’s backing, Jai Singh built his first Jantar Mantar in Delhi in 1724. In 1728, the construction of another observatory began in Jaipur, Jai Singh’s new capital, which he had founded in the previous year.

Instruments of the Jantar Mantar

This Jantar Mantar in Jaipur was built on a plot of land just outside the City Palace and is situated within the walls of the original city. This is the largest of the five observatories that Jai Singh’s built, and is one of the best-known and most visited Jantar Mantar, since it is located in a major tourist destination.

More importantly, the Jantar Mantar in Jaipur is the most complete and elaborate of Jai Singh’s observatories, as it possesses the greatest number and variety of instruments. Some of the instruments, it may be added, are unique to this observatory. In total, the Jantar Mantar in Jaipur houses 22 astronomical instruments, 16 of which are masonry instruments, while the other six are made of metal.

One of the most impressive astronomical instruments at this observatory is the Samrat Yantra, which is sometimes called the ‘Supreme Instrument’. This is an equinoctial sundial and is little different, in terms of design, from other sundials that were being used in the preceding centuries. Jai Singh’s sundial, however, exceeds these other sundials in its precision, being capable of measuring time to an accuracy of two seconds.

In order to achieve this level of precision, the size of the instrument had to be huge. Therefore, standing at a height of 88 feet (27 meters), the sundial at Jaipur’s Jantar Mantar is the largest in the world.

Sundial at Jantar Mantar observatory. (travelview / Adobe Stock)

Sundial at Jantar Mantar observatory. (travelview / Adobe Stock)

While the sundial is one of the simpler instruments at the Jantar Mantar, Jai Singh also had more complex pieces made for his observatories. One of the most complex of these is the Jai Prakash Yantra (which translates to mean ‘Light of Jai Instrument’). A description of how the instrument works is as follows:

“The Jai Prakash is a bowl shaped instrument, built partly above and partly below ground level, …. The interior surface is divided into segments, and recessed steps between the segments provide access for the observers. A taut cross-wire, suspended at the level of the rim, holds a metal plate with circular opening directly over the center of the bowl. This plate serves as a sighting device for night observations, and casts an easily identifiable shadow on the interior surface of the bowl for solar observation. The surfaces of the Jai Prakash are engraved with markings corresponding to an inverted view of both the azimuth-altitude, or horizon, and equatorial coordinate systems used to describe the position of celestial objects.”

Yet another instrument found in the Jantar Mantar is the Rama Yantra, which consists of “a pair of cylindrical structures, open to the sky, each with a pillar or pole at the center. The pillar/post and walls are of equal height, which is also equal to the radius of the structure. The floor and interior surface of the walls are inscribed with scales indicating angles of altitude and azimuth”.

Astronomical instrument at Jantar Mantar observatory – the Rama Yantra. (travelview / Adobe Stock)

Astronomical instrument at Jantar Mantar observatory – the Rama Yantra. (travelview / Adobe Stock)

This astronomical instrument is used to “observe the position of any celestial object by aligning an object in the sky with both the top of the central pillar, and the point on the floor or wall that completes the alignment”. It has been claimed that the Rama Yantra, along with the Jai Prakash and the Samrat Yantra were devised by Jai Singh himself, and that to some extent, their design ought to be attributed to the king’s personal ingenuity.

Decline of the Jantar Mantar

When Jai Singh died in 1743, his kingdom began to enter a period of decline, as his sons fought each other for the throne. At the same time, the Mughal Empire was weakening and was in fact breaking up. As a result, northern India became vulnerable and various powers seized the opportunity to attack the region.

Delhi was especially targeted, due to the riches it contained. For instance, the city was sacked by the Iranian ruler, Nader Shah, when he invaded northern India in 1739. In 1748, after the death of Muhammad Shah, the Marathas overran almost all of northern India. The Jantar Mantar at Delhi fell victim to these invaders.

Jantar Mantar astronomy instrument, New Delhi, India. (Akhilesh Sharma / Adobe Stock)

Jantar Mantar astronomy instrument, New Delhi, India. (Akhilesh Sharma / Adobe Stock)

The natural environment is also responsible for causing much damage to the Jantar Mantar. Due to their outdoor situation in a tropical area, maintenance and restorations had to be frequently carried out on the Jantar Mantar.

As a result of the political turmoil in the region, however, the successors of Jai Singh had more pressing matters to attend to. As a consequence, maintenance of the observatories was neglected and they were simply left to deteriorate.

During the 19th century, even the Jantar Mantar at Jaipur was temporarily abandoned. Fortunately, reconstructions of the instruments were made for this Jantar Mantar, and in the subsequent decades, efforts were made to maintain the site.

Taken from the observation platform at the top of the Jantar Mantar in Jaipur, India. (Knowledge Seeker / Public Domain)

Taken from the observation platform at the top of the Jantar Mantar in Jaipur, India. (Knowledge Seeker / Public Domain)

Today, this Jantar Mantar functions as a tourist attraction, and is used also as a public park and outdoor museum. Nevertheless, the deterioration of the instruments remains a problem even today. Weathering, the wear and tear of materials, as well as vandalism pose a threat to the site.

In 2010, it was reported that the biggest issue is the loss of the fine, calibrated markings on the instruments, which are eroding. These astronomical instruments demonstrate the ingenuity of Jai Singh and his achievements in the field of astronomy. Therefore, their deterioration needs to be addressed as soon as possible, so as to preserve these remarkable instruments for future generations.

Top image: Jantar Mantar in India. Source: Aliaksei / Adobe Stock.

By Wu Mingren


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Wu Mingren (‘Dhwty’) has a Bachelor of Arts in Ancient History and Archaeology. Although his primary interest is in the ancient civilizations of the Near East, he is also interested in other geographical regions, as well as other time periods.... Read More

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