Largest Sundial in the World !

A sundial is a device that measures time by the position of the Sun.

Standing 27 metres (90 feet) tall and with a base length of 147 feet, the Vrihat Samrat Yantra (The Large Supreme Instrument) is the world’s largest sundial !

It is housed in Jantar Mantar ( literally means 'calculation instrument') in Jaipur, in the state of Rajasthan.

It’s shadow moves visibly at 1 mm per second, or roughly a hand's breadth (6 cm) every minute,
It's face is angled at 27 degrees, the latitude of Jaipur. The Hindu chhatri (small cupola) on top is used as a platform for announcing eclipses and the arrival of monsoons.

Used for calculating the time of the day to the exact second using the position of the dial and the shadow it casts from the sun, it has an accuracy of about two seconds. If an astronomical observer knew the time it took a prominent star to transition the sky, they could even use the Yantra to tell the time at night.

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Largest Stone Astronomical Observatory in the World !

Located across the road from the City Palace, Jantar Mantar, was our next destination in Jaipur.

It:
- Was built between 1727 and 1733.
- Is the largest stone astronomical observatory in the world !
- Has the biggest sundial in the world !
- Is one of the largest and the only working observatories of the five, built by Sawai Jai Singh II (the others were built in Delhi, Mathura, Benaras and Ujjain)
- Houses a large collection of around 20, huge masonry astronomical instruments, each with a specific astronomical use. The main reason to build these large stone structures on a grand scale was to enhance the accuracy of the measurements.
- Has been recently (in July 2010), added to the World Heritage list, by UNESCO, as a cultural site.
- According to UNESCO, the site "is the most significant, most comprehensive, and the best preserved of India's historic observatories."



As listed on the National Geographic site, the other astronomical site added to the World Heritage list is part of the monuments at "The Centre of Heaven and Earth"—a sacred mountain in China's Henan Province.
The site includes the Zhougong Sundial Platform and the Dengfeng Observatory, built about 700 years ago at the beginning of the Yuan Dynasty (A.D. 1271-1368) by astronomer Guo Shoujing.
Reference: http://blogs.nationalgeographic.com/

I admire our astronomers and masons of yesteryears who conceived and built these amazing masonary instruments used to study the movement of constellations and stars in the sky !