Raja Sawai Jai Singh constructed the Jantar Mantar during the early 18th century AD.
He named this observatory as ‘Yantra Mantra’, of which Yantra means instrument, while Mantra means formula.
During British era, the name got corrupted to Jantar Mantar. This place has four main instruments – The Ram Yantra, The Jayaprakasha Yantra, The Misra Yantra and the Samrat Yantra.
The Ram Yantra is designed to determine the local celestial co-ordinates and has two complementary buildings in a circular shape.
The Jayaprakasha Yantra has two complementary concave hemispheres that reflect the dome of the sky and is used to show the zodiac signs, the Sun’s declination and the local time instantaneously.
The Misra Yantra is used to find out the shortest and longest day of the year. The Samrat Yantra is an equinoctial Sun Dial and was used to calculate precise time of the day in split second and the Sun’s declination.
The Jantar Mantar is situated on Parliament Street and can be seen from 9 am to 7 pm without any entry fee.
The Remarkable Structure
 It is a remarkable structure which consists of fourteen geometric devices used for measuring time, forecasting weather changes, predicting behaviour of planets and finding extraterrestrial altitude. All these devices are fixed structures and point to a specific direction. The largest device or instrument is the Samrat Jantar which is 90 feet high and its shadow is plotted in such a manner so that is shows the exact time of the day. Any weather change or the onset of monsoons can be ascertained by the Hindu Chhatri, which is a small domed structure.
The whole structure is made of stone and marble with each of then having an engraved astronomical scale. Jantar Mantar finally got the status of a national monument in 1948. It has always attracted architects, historians and scientists from all over the world.
Maharaja Jai Singh
Maharaja Jai Singh was a fanatical astronomer himself who studied various works from Hindu, Muslim and European astronomy. He had the perception that the tables used by the pundits were deceptive and the actual planetary changes and predictions of eclipses would not have been possible through these measuring parameters. So he thought that he would find an improved and efficient means through which exact prediction could be made. It was his own inspiration and foresightedness that gave shape to such an instrument. He built other observatories at Jaipur, Ujjain, Benares and Mathura to have an exact calculation. It took almost seven years before the whole structure was fully operational because he wanted to be fully satisfied with the accuracy of the instruments at Jantar Mantar.
Purpose of Individual Structures
There are four distinct instruments within the observatory of Jantar Mantar:
The Samrat Yantra,
The Ram Yantra,
The Jayaprakash,
The Mishra yantras.
Samrat Yantra:
The Samrat Yantra, or Supreme Instrument, is a giant triangle that is basically an equal hour sundial. It is 70 feet high, 114 feet long at the base, and 10 feet thick. It has a 128-foot-long (39 m) hypotenuse that is parallel to the Earth's axis and points toward the North Pole. On either side of the triangle is a quadrant with graduations indicating hours, minutes, and seconds. At the time of the Samrat Yantra's construction, sundials already existed, but the Samrat Yantra turned the basic sundial into a precision tool for measuring declination and other related coordinates of various heavenly bodies.
Ram Yantra:
Ram Yantra consists of two large buildings with open top. Both these two buildings form a complete device. The device is used to measure the altitude of stars which is equivalent to the latitude and the longitude on the earth.
Jayaprakash Yantra:
The Jayaprakash consists of hollowed out hemispheres with markings on their concave surfaces. Crosswires were stretched between points on their rim. From inside the Ram, an observer could align the position of a star with various markings or a window's edge.
Mishra Yantra:
The Mishra yantras were able to indicate when it was noon in various cities all over the world and was the only structure in the observatory not invented by Jai Singh II.
Time of Equinox
The sun's position at the time of equinox. There is a hole near the bottom of the structure which witnesses sunshine only once in a year that is on 21 march, called vernal eqinox.
It is no denying the fact that the structure does represent the scientific heritage of India, though not being used in the modern scientific research. Having said that, we must give accreditation to the Jantar Mantar for its scientific acumen which could have reaped more fruits had there been appropriate motivation and resource given for research and development.
Location:
Jantar Mantar, a historic places of Delhi, is situated in heart of Delhi near Connaught Place.
Source: Wikipedia
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