“Hemispheres hollowed out with markings inside.” That’s the Jai Prakash Yantra before you. This structure stands as a testament to India’s rich knowledge of astronomy. It was built in 1724 by Maharaja Jai Singh II. He was the founder of Jaipur.
The name “Jantar Mantar” comes from Sanskrit words. “Yantra” means instrument. “Mantra” means formula. So, it means instruments for measuring the sky. This Jai Prakash Yantra is near Connaught Place. It is one of five observatories built by the king. The others are in Jaipur, Ujjain, Mathura, and Varanasi.
Sawai Jai Singh set up three large instruments. They read the time and observed celestial coordinates. The Jai Prakash Yantra is one of them. It has two halves, like hemispherical bowls. They are partly set into the ground. They are partly above. The bowls have markings on evenly spaced slabs. These are on the floor.
Any marked surface in one bowl is a gap in the other bowl. It is vice versa. The gaps let observers move around. They stand while the shadow of the object falls on a marked surface. When the shadow falls on a gap in one structure, it falls on a marking in its twin. The observer reads the shadow. They either move across to the twin instrument. Another observer is already stationed there.
The Jai Prakash Yantra’s bowls were constructed as a reflection of the night sky. Inside the dome, there is a slot. It attaches a pole extending to the top of the instrument. The observer adjusts their eye. The celestial object appears right on the tip of the pole. They note the reading marked on the scale adjacent to the eye.
The readings in the Ram Yantra are for azimuth and altitude. The readings in the Jai Prakash Yantra were possibly for right ascension and declination. The original markings in the Jai Prakash Yantra were replaced during a restoration. That was in 1910. Even those markings are barely legible now.
Each instrument at Jai Prakash Yantra was designed for precise astronomical calculations. It measures the movement of the sun and stars. The Jai Prakash Yantra features hollowed-out hemispheres. There are markings on their concave surfaces. Observers inside align the position of a star with various markings. This determines celestial coordinates.
The Jai Prakash Yantra and other instruments reflect India’s advanced understanding of astronomy in the 18th century. Admire the Jai Prakash Yantra. It is a testament to India’s architectural brilliance. It combines science and architecture. It showcases India’s astronomical expertise.