Time bound

When I was a young boy I read a story called Intangibles Inc, in which a corporation sells intangibles, such as a purpose to your life. Our trip to Ujjain turned out to be similar. Ujjain has a history older than Rome or Xi’an. One of the most ancient pieces of lore about the city is that it lay at the intersection of the prime meridian and the Tropic of Cancer. This prime meridian is one of the many intangibles that dogged our half day in Ujjain.

Different cultures use different prime meridians, and the one that used Ujjain’s longitude is the ancient Hindu culture, whose computational apparatus is still embedded into the religious calendar. The computational recipes can be found as poems in a text called the Surya Siddhanta (which would translate as Solar Treatise). The oldest version of these algorithms comes from a manuscript written before the birth of Alexander, and probably collects together recipes known from significantly older times. This book places Ujjain at the center of its computational cosmos. The standard day, for example, began at the time of sunrise in Ujjain.

As a practical matter, I knew that Ujjain would be like Banaras, full of medieval rituals and 18th century temples located in a city which is older than recorded history. The oldest sites that we know of are ancient temples, and even these are only at about the midway point between us and the oldest known version of the Surya Siddhanta. I had read about parts of temples which were a little less than a thousand years old. I created a detailed map of these locations, although I did not expect to be able to access these spots. I was right. Eventually, walking through Ujjain gave us only an intangible connection to the oldest history of humanity.

So I was happy to walk into an observatory built here by Sawai Jai Singh in 1725 CE. He was a Mughal courtier, the king of Amber, the founder of the city of Jaipur, an avid amateur astronomer, and a scholar. He assembled a team of astronomers from three cultures: those who knew the Hindu astronomical texts, a set of people who knew the Islamic texts on astronomy, and a company of Portuguese Jesuits who knew European astronomy. He sent delegations abroad to collect books and learn about astronomy from foreigners. Eventually he built five observatories in various parts of India, driven by a perception that accuracy is important. The time-keeping instruments in the observatory in Ujjain would connect this 18th century structure to the most ancient text that we have regarding Ujjain.

The computations of the Surya Siddhanta were clearly incorrect by the early 18th century CE. Many of the numbers in the treatise are correct only to 1% by modern standards. This is true, for example, of the statement that Ujjain is on the Tropic of Cancer. If that were correct, then Ujjain should have been 57 Kilometers north of its position. This is an error of almost 1%.

Sawai Jai Singh’s instruments are built in masonry, as you can see in these photographs. All four photos show what he called the Samrat Yantra of Ujjain, something that we would call today an Equinoctal Sundial. It is built large in order to gain accuracy (this sundial gives an accuracy of about 2 seconds in the measurement of local time). The photo above shows the gnomon which casts a shadow on the dial whose photo you can see below. In the featured photo you can see how the gnomon and the dial are placed.

The huge gnomon points towards the true north. So the staircase makes an angle to the ground which is exactly the latitude at the spot where it stands. This is the principle of the equinoctal sundial. At the base of the staircase which is this large gnomon you can see a barrel with two smaller sundials. These are oriented in such a way that on the days of equinox you can tell the time by either. In summer the south-facing one (visible in the featured photo) will be in shadow, and in winter the north-facing one (visible in another photo above) would be unusable because it will be in shadow. We walked around this instrument on the birthday of Alexander the Great, when weather conditions in India generally render any sundial useless.

This gave us time to consider the greatest mystery about Sawai Jai Singh. Although he assembled a stellar cross-cultural school of astronomers, how did he miss out on the most important advances in astronomical history? Why did he continue to improve an outdated medieval astronomy? Galileo had invented the telescope in 1609 CE. Copernicus had published his treatise on the heliocentric system in 1543 CE. Newton’s Principia Mathematica was published in 1687 CE. And Sawai Jai Singh was eager enough (for a king) to learn about the most advanced work on astronomy from across the world. What went wrong? I asked The Family these questions as we walked around the observatory.

The answer that I find most believable is given by Prof. Virendra Nath Sharma (a copy of his paper is here, and a refutation is here). Prof. Sharma holds the Portuguese team of Jesuit priests responsible for this. He thinks that they followed the church’s proscription against teaching the Heliocentric system and Galileo. But this does not explain why Jai Singh’s team did not learn about the Vernier scale, which were invented in 1631 CE. The intangibles keep adding up.