Jaipur, home to the largest sundial in the world
Scholars agree that the astronomical and astrological observatory founded by Maharajah Jai Singh II remains a marvel of scientific precision. Situated 220 km south-west of Delhi, it is now also a tourist attraction.
Gian Pozzy
Among statesmen’s many preoccupations is the desire to immortalise their supposed greatness in bricks and mortar. For better and for worse. From the hanging gardens of Babylon to the Louvre’s glass pyramid, from Napoleon’s Arc de Triomphe to Félix Houphouët-Boigny’s basilica in Yamoussoukro, thousands of elaborately-maintained buildings across the globe set more or less ephemeral and glorious achievements in marble and stone.
Astronomy serving astrology
Jai Singh II, Maharajah of Jaipur (Rajasthan) from 1699 to 1743, took this desire to leave a mark on history to the extreme. Over a period of four years he built, from nothing, the capital city - Jaipur - of his kingdom. With avenues 34 metres wide, and no street less than four metres in length, the maharajah’s city was more akin to Baron Haussmann’s Paris than the tangled mazes of Calcutta! And because Jai Singh II was no ordinary autocrat but an enlightened scholar too, he had an observatory erected opposite his palace. It remains the largest and most impressive astronomical site the world has ever known. Its name: Yantra Mandir or Jantar Mantar, depending on the transcription.
Mankind has always been fascinated by the heavens. Clearly, the sun’s journey through the sky from dawn to dusk, the phases of the moon and "the dim light that falls from the stars" (Corneille) were in some way connected to the endless progression of time. Here was something great, powerful, mysterious and superhuman that gave not just the hours and the seasons but was the manifestation of a superior will. And so from Nebuchadrezzar to Jai Singh II, astronomy was seen as the key to perfecting astrology: plotting astral charts, forecasting auspicious moments for important decisions, staying home under the covers on ill-omened days…
Jantar Mantar and its seventeen astronomical instruments
And so Jai Singh II set his sights high. Between 1724 and 1727, he ordered the construction of five astronomical observatories in Delhi, Jaipur, Ujjain, Varanasi and Mathura. All except the latter still exist, but Jantar Mantar is the most spectacular. One of its most noteworthy instruments is the Samrat Yantra, the world’s largest sundial - its gnomon stands 24 metres high - which measures apparent solar time. It even measures time at night, provided the observer has a certain knowledge of the movement of the stars, specifically that a star makes a complete revolution of the Earth in 23 hours, 56 minutes and 4.09 seconds which is the length of the sidereal day. The time at night can therefore be measured by observing the star’s angular distance from the meridian. At the equinoxes, the Samrat Yantra indicates time to within half a second. For the rest of the year its subdivisions give a reading that is accurate to within two seconds! To rival the accuracy of this celestial timekeeper is a challenge even today.
There are seventeen instruments in all at the Jantar Mantar observatory in Jaipur. These include:
• Jai Prakash, an elaborate instrument based on a concept that was already known in 300 B.C. when the Greco-Babylonian astronomer Berosos made a hemispherical sundial (examples of which were built in medieval European church architecture and at the Nanking observatory in China in the late thirteenth century). Two precisely-graduated hemispheres, each five metres in diameter, indicate the position of any celestial body.
• Ram Yantra, which comprises two cylindrical structures used to measure the altitude and azimuth of the planets on graduations engraved on the walls and floor.
• Rashivalaya Yantra with its twelve dials, each facing a constellation of the zodiac. They measure elliptical coordinates.
• Chakra Yantra, which measures the equatorial coordinates, hour angle and distance of a celestial body.
• Shasthansa Yantra is an arc graduated into degrees and minutes and placed inside a dark chamber with a single pinhole in the wall. When the sun passes in front of this pinhole the ray of light can be used to measure, among other things, the zenith distance and the diameter of the sun.
First the Vatican
No doubt Jai Singh II had prior knowledge of this latter instrument. Certainly a similar device already existed at the Vatican, inside the Tower of Winds which was built between 1578 and 1580, a commission to the architect Ottaviano Mascherino from Pope Gregory XIII. In addition to the anemometer which gave the tower its name, the papal astronomer and member of the calendar reform commission Ignazio Danti made a meridian line, a marble line on the floor running north to south and which measures the height of the sun at noon according to the season: a ray of sun enters the tower through a hole in its southern wall and projects a spot of light on the graduated meridian line.
Observing this ray of light, it became clear that the Julian calendar, named after Julius Caesar, had done its time and should make way for the Gregorian calendar which four centuries later still counts our days and months. ■
Aee also:
Jantar Mantar virtual tour
Tower of Winds
