Jantar Mantar - Indian Astronomical Observatory - Sundial

Jantar Mantar is a colossal astronomical observatory, near Parliament Street and Connaught Place, New Delhi, India. It contains masonry structures of various shapes and sizes, built to study and calculate the movement of the stars and planets. Jantar Mantar, also known as Yantra Mantra, literally means "Jantar or Yantra = Instrument, Mantar or Mantra = Formula".

Maharaja Sawai Jai Singh II of Amber (the city Amber is now known as Jaipur), built this astronomical observatory at Delhi along with four other observatories at Jaipur, Varanasi, Ujjain, and Mathura during AD 1724 - 1730.

All the observatories have sundials besides other structures to calculate celestial co-ordinates.

The builder of Jantar Mantar

Maharaja Sawai Jai Singh II (November 3, 1688-September 21, 1743) ascended the throne of Amber in 1699 at the age of eleven years due to the untimely demise of his father Maharaja Bishan Singh. At such a tender age, he was extremely knowledgeable and shrewd far beyond his years. The last Mughal emperor Aurangzeb bestowed on him the title of "Sawai", which means "one and quarter", because he was one and quarter times superior to his contemporaries. He was thoroughly conversant with the Hindu, Muslim, Greek, and European schools of astronomy.

He studied Ptolemy's Syntaxis, Flamsteed's Historia Coelestis Britanica, Euclid's Elements, Newton's Principia, de la Hire's Tabulae Astronomical, and the Astronomical Tables of Mirza Ulugh Beg of Uzbekistan. He also commanded knowledge of the master treatises of Varahmihira, Aryabhatta, Bhaskaracharya and Brahmagupta. Muhammad Shah, who ascended the throne of Delhi after Aurangzeb wanted accurate predictions to undertake new ventures and to win over rising enemies to establish his supremacy. Upon the request of Muhammad Shah, he built the five observatories, naming them as Jantar Mantar.

The raison d'être of Jantar Mantar

Due to the lack of precessions of the rotation of the earth's axis, an effect known as Ayanamasa was noted since early times. Ayanamasa created a difference in the calculated and predicted elements, which underwent ad-hoc corrections known as Bija corrections. For precise observations that would not require these Bija corrections, Jantar Mantar was built with brick and plaster consisting of large interlocked and extruded shapes, instead of relying on small brass instruments. The observatory at Delhi was completed in 1724.

Due to the power struggle going on in the capital, it was in operation only for a period of seven years and the observations were compiled as Zij Muhammad Shahi, which is a set of astronomical tables. Today all the five observatories are in disuse, and serve only as specimens of scientific heritage.

The structures of Jantar Mantar, Delhi

• Samrat Yantra - This is an equinoctial sundial. This is the largest structure. This can measure the time of the day with accuracy of within half a second. Maharaja Sawai Jai Singh II himself designed this sundial.
• Misra Yantra - This is a combination of four different structures. It was used to measure the declination of the sun, plot the course of heavenly bodies, and predict eclipses. On the southwest, there are two pillars that can determine the longest and the shortest days of the year. During December, the shadow of one pillar completely covers the other pillar, while during June, the pillar does not cast any shadow on the other pillar.
• Jayaprakash - This consists of two semicircular domes, reflecting two hemispheres of the sky.
• Ram Yantra - This consists of two circular complimentary structures. It was designed to make the determination of local celestial co-ordinates easy.