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If you are a resident of Delhi, and have taken visiting relatives to the Jantar Mantar, you could be one of the many who are befuddled by the strange and confusing masonry structures there. Structures said to have been built early in the 18th century by Raja Swai Jai Singh of Amber. Most residents of Delhi, are perhaps more aware of the Jantar Mantar as a place where political protests take place.
On the other hand, you may be one citizen of Delhi, who has more of an Astronomical or Scientific interest and would perhaps be aware that the Jantar Mantar was a complex of masonry instruments that were built for Astronomical observations. Some inkling would also be there, that, perhaps, some of these instruments are some kind of Sun dials. Beyond that, it is not an easy matter for someone looking for more detailed information about these structures, to obtain. Very little literature seems available about the actual usage of these instruments.
After being built, how long were they used for the purpose for which they were built? When did they fall into disuse? Are they currently in any possible usable state? If at all usable, what kind of usage would be possible with these medieval instruments in the modern day world? And finally, what exactly were these strange instruments supposed to measure?
The same questions would have bothered many Indians with an interest in Astronomy. A few answers can be glimpsed here and there, from their efforts. In recent time, Nehru Planetarium, New Delhi, has been one center with a lot of interest in understanding and using the Jantar Mantar instruments, for Astronomical observations. The Ram Yantra and Jai Prakas Yantra at the Delhi Observatory were successfully used by Nehru Planetarium staff, amateur astronomers and students, during March 2004 to measure the maximum angular movement of Venus, away from the Sun - an important ingredient that then went into the determination of the Earth Sun distance, using later observations of the June 8, 2004 Transit of Venus.
Nehru Planetarium, New Delhi, in collaboration with other organizations involved in Science and Astronomy education - Amateur Astronomers Association, Delhi, Vigyan Prasar and Science Popularisation Association of Communicators and Educators (S.P.A.C.E., an NGO), is planning a public event of observations and calibrations of the four main Jantar Mantar instruments - the Samrat Yantra, the Misra Yantra, Jayaprakas and the Ram Yantra, on the 20th of March, 2005.
The date happens to be when the Spring equinox occurs, this year. This is one of the two days in the year when the sunrays are perpendicular at the equator and the lengths of the day and night are equal. We cannot see the background stars, in the daytime, when the Sun is above the horizon. Otherwise, we would be able to see that, this is the time when Sun appears against the background of the Zodiacal constellations Pisces and Aquarius.
Why go to the Jantar Mantar specially on the equinox day? Well, it is an observatory meant for Astronomical observations at any time of the year and day, but, there are many interesting aspects of the Observatory, related to such special days in the year - as equinoxes and solstices.
There are four main instruments in the Jantar Mantar Complex at Delhi - the Samrat Yantra, Misra Yantra, Jaiprakas and the Ramyantra. Of these the Samrat and the Misra Yantra have the main functionality of a Sun dial, with calibrations for reading the time from the daily East-West movement of the Sun. Most of these calibrations are now obliterated from the instruments. These two instruments also have some additional functionalities of measuring celestial co-ordinates of the Sun and the stars, with interesting variations.
It is when visitors come to the South side of the complex, that they are completely at sea, as to the functionality of the twin bowls of the Jaiprakas or the twin cylindrical instruments of the Ram Yantra. These very interesting instruments can be used for measuring the co-ordinates of objects in the sky much more completely than the Samrat and Misra Yantra can. In fact, the Jaiprakas and Ram Yantra together would make a wonderful laboratory for any school or college student to determine their own tables of co-ordinates of celestial objects. They can be particularly useful, when a bright comet appears in the sky, for instance. The movement of the comet against the background of the stars can be very effectively studied using these instruments. The instruments are in a little disrepair, of course, and a little effort in the direction of redrawing the markings on these instruments could go a long way towards making these instruments actual, live laboratories that could be put to use for student projects.
The most poignant aspect of this magnificent observatory is to do with the fact that, it was an anachronism even when it was built. The type of instruments here, were already obsolete at the time they were built - as far as obtaining new results was concerned. Jai Singh’s idea, that large size of the masonry instruments would give better and better accuracies of celestial co-ordinates, had already been washed out by the introduction of the micrometer screw gauge in a telescope. Much higher accuracies of celestial position determination had become possible with such instrumentation by early 18th century. However, the knowledge of these advances did not reach Jai Singh, though, he was aware of the invention of the telescope. He perhaps had tried an inferior make of a telescope or one without a micrometer gauge for precise measurements and opted for the construction of gigantic masonry instruments for precise measurements. He did obtain reasonable estimates of celestial co-ordinates for a number of objects in the sky - which was no mean achievement. In addition to this, he also had another usage for the instruments - that of making it easy for the aam aadmi to do such observations on their own. How many people, amateur astronomers included, would have a knowledge of the usage of a micrometer screw gauge or a similar instrument on a telescope that would tell them, where exactly in the sky a celestial object is located? And yet, many visitors who had visited the Jantar Mantar on the 29th of March 2004 and had done their own observations with help from volunteers from the Nehru Planetarium, had found it such an easy exercise - not only to quantitatively determine the location of the Sun in the sky, but, also to appreciate the significance of such determinations.
Thus, anachronism or not, the instruments at the Jantar Mantar, have a wonderful utility of making Astronomy observations user friendly. It is this aspect that needs to be celebrated. 300 years after they were built - they are still the easiest access a student (of Delhi, or Jaipur) could have, of doing quantitative celestial co-ordinate measurements. If you wish to experience the thrill of doing such measurements, and participate in a public contest of doing such observations, with some guidance from volunteers present there - be sure to keep your date with Raja Jai Singh at the Jantar Mantar, on the 20th of March, 2005. Volunteers will be present to give guidance for observing the co-ordinates of the Sun, between 11 AM to 5 PM on this day. After every training session - public and students will be allowed to make their own measurements, to be compared with calculated elements and trophies will be given to those who come up with good accuracies of measurements!
The program for the 20th will involve measurement of the co-ordinates of the Sun at 10 minute intervals, between 11 AM and 5 PM, using the Jaiprakas and the Ram Yantra. Marking the location of the Sun, on the bowl of the Jai Prakas, will trace out the celestial equator on this bowl - as the Sun is at the junction point of the celestial equator and the ecliptic (apparent annual path of the Sun), on this day.
Some calibration measurements will be made between about 3 PM and 5 PM on the quadrants of the Samrat Yantra. Most interesting will be some observations with the Misra Yantra - finding out the time when Sun is overhead at Delhi, at Zurich and at Greenwich and tallying the co-ordinates of the Sun obtained at these three different times.
All in all, it promises to be a very fruitful spring festival this equinox on the 20th of March - keep your date with the Raja of Amber.
*Director, Nehru Planetarium, New Delhi.
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