Jantar Mantar 🇮🇳

A Jantar Mantar is a historic complex of stone-built astronomical instruments designed for naked-eye celestial observation. Between 1724 and 1735, five of these observatories were constructed across North India at the command of Sawai Jai Singh II of Jaipur, who maintained a strong interest in mathematics, architecture, and astronomy. The sites were established in Jaipur, New Delhi, Ujjain, Varanasi, and Mathura. Today, four of these locations survive, as the observatory at Mathura and its protective fort were destroyed prior to 1857.

The name Jantar Mantar has been used for over two centuries, appearing in a written account from 1803. The term originates from the word yantra, meaning instrument, which became jantra in local spoken language. The second word, Mantar, stems from mantrana, which means to consult or calculate. Historical records from the Kingdom of Amber dating to 1735 and the years 1737 to 1738 originally referred to the installations simply as Jantra.

These astronomical compilations, also referred to as Mishra Yantra or mixed instruments, were created primarily to calculate astronomical tables and to predict the exact movements and timing of the Sun, Moon, and planets. Each site brings together up to 19 distinct astronomical devices. Among the specific instruments built across the observatories are the Jai Prakash Yantra, Disha Yantra, Rama Yantra, Chakra Yantra, Rashiwalya Yantra, Dingash Yantra, Utaansh Yantra, and the Samrat Yantra.

The Jaipur assembly is the largest of the sites and has been designated a UNESCO World Heritage Site. Its most prominent instrument is the Samrat Yantra, an equinoctial sundial that holds the distinction of being the largest stone sundial in the world. This structure features a massive triangular gnomon with its hypotenuse set parallel to the axis of the Earth, flanked on each side by a circular quadrant aligned with the plane of the equator. When operated by a skilled observer, this instrument can measure the time of day and determine the declination of the Sun and other celestial bodies with an accuracy of roughly 20 seconds.