The full article with pictures and diagrams can be downloaded at
http://www.ias.ac.in/currsci/dec102008/1632.pdf


A short synopsis of the article appeared in deccan herald below.

Astronomical significance of the Gavi Gangadhareshwara temple in Bangalore

The famous event of the suns rays bathing the Shivalinga at the Gavi Gangadhareshwara temple takes place not just on January 14, but in the course of this week too, according to B S Shylaja. When you visit this famous temple, take a look at the two huge stone chakras; they mean something hitherto unknown, she explains.

Several years ago I came across a book of paintings; running through its pages was like turning the pages of history,  pictorially. The paintings were the creations of Daniell brothers, Thomas and William, who visited India during 1790- 94. One painting caught my attention. It was familiar. No other temple in India has such beautiful large stone discs. Yes, that was the famous Gavi Gangadhareshwara temple at the heart of Bangalore.  This temple had earlier tickled me for another reason. That is Surya Majjana, the phenomenon of the sun’s rays making their way through the windows to shine on the Linga inside the cave. Why on a specific date? This question had me thinking. That there has to be another day in the year when this would happen again, bothered me constantly. My calculations gave me the dates too. I had been making desperate attempts to verify it for almost for six years.  Then it happened a couple of years ago. A couple of acquaintances waited patiently every evening at the temple. The door would be open only if it was a Monday; otherwise one had to look through the window. All three of us managed to get a glimpse of the sunlight shining on the idol over a five-day stretch from November 26 to December 2.  The fact that there is a second Surya Majjana was not known to many and unfortunately was not received very enthusiastically. We tried in 2007 again and got the dates confirmed.  So now it is for any one of you to go to the temple and see the same Surya Majjana event that is slated for January 14. So, what is significance of these dates? It is a simple consequence of the apparent movement of the sun in the north- south direction. As is well known, there are four important dates in a yea. March 21 is the vernal equinox, the onset of spring and new year celebrations are all associated with it. Then, there’s June 22,  marking the end of summer. The sun is in the northern-most position on this day, making it the longest day. Then begins the southward journey; so the day is aptly termed Dakshinayana. The day gets shorter thereafter. The duration of the day is equal to that of the night on September 22 . This day is called the autumnal equinox. The length of the day shrinks and reaches a minimum on December 22. That is the southernmost limit the sun can reach. His northward begins on this day called Uttarayana. Thus, except June 22 and December 22, for any other day the position of the sun is repeated on a second day.  We had deduced the dates for the Surya majjana event of Gavi Gangadhareshwara temple on this premise. Unlike most of the temples, this one does not face the east or even the west. The orientation seemed intriguing and fixing the north-south directions was very tricky. I searched for ground plans – none existed. I prepared my own plan. Then it occurred to me that the two huge discs in front of the temple have a special significance. So my trips to the temple extended to other dates in the year. The discs are indeed special. Just as the entry to the cave marks the direction of the sun close to winter solstice, these two discs indicate the direction of the sun around summer solstice. By June 16, the shadow of the western disc started appearing on the wall behind the eastern disc. I sketched the scene and extrapolated the movement of the shadow to sunset because the trees blocked the sunlight. My calculations showed that if one can let unobstructed sunlight reach the discs, the shadow of the western disc would fall on the eastern disc. This happens only on June 22 and for a few days on either side of it. We also noticed that the shadow of the brass Dhwajasthambha falls exactly at the centre of the eastern disc about half an hour before sunset. Therefore this appears to be a unique cave temple designed for the purpose of marking solstices. Historians have mentioned only the January 14-event probably either because of the harvest festival associated with it or because the second set of dates was simply not known to them. Or was there any other reason? This is where the painting of Daniell gave me the clue. The two discs and the trident appear intact. The painting is dated 10 May, 1792. However, a careful analysis reveals some differences. Most importantly, there are no windows to let the sunlight for Surya Majjana. (There is a second painting of Hunter dated 1806; it does not provide this view.) The absence of Dhwajasthambha is very conspicuous. (The bronze cover is dated 1979). So is the small Mantapa which houses a Nandi. The gradual slope of the hillock is now converted into steps. Furthermore, there are three arch-like structures which are missing now. It appeared to me that in the last 200 years, some renovation has been done. The three arch-like structures then were enclosed inside a larger Mantapa. The two rows of pillars have a roof which is not part of the hillock. Thus the temple got a complete facelift. The idea of sun’s rays falling on the idol was perhaps known to the renovators. They took care to install windows so as to let the phenomenon continue. The terms Uttarayana and Makara Sankranthi were considered synonymous. Therefore the windows were aligned for Makara Sankranathi. Similarly the Dhwajasthambha was matched for summer solstice (Karkataka Sankranthi) and eventually forgotten. The second painting of Daniell provides the view of the surroundings. Two hundred years ago, the region was barren offering a clear view of the horizon. The place between temple and the gopura was perhaps a water drain. In the event of visibility of the horizon the discs serve a dual purpose, they mark the sunrise of winter solstice and sunset of summer solstice. Does that mean people who used this cave were dedicated astronomers? Daniell in his footnote mentions that this was a deserted temple. Was it? Or was the purpose beyond the comprehension of Daniell? Historians may have the answers. Who knows, this temple could have been a school  of astronomy ? Deccanherald.com (The author is with BASE, Jawaharlal Nehru Planetarium, Bangalore. Website: taralaya.org)