Jaipur is only four and a half hours by train from Delhi (a mere nothing for India) so I spent the day sightseeing before taking the evening train. Jaipur has some other wonderful sights, but only this one is UNESCO listed.
The Jantar Mantar is a group of around twenty monumental scientific instruments for naked-eye astronomical observation and measurement, dating from the early eighteenth century. It is the largest and best preserved of five such observatories built by Maharaja Jai Singh II, a Hindu ruler with a great interest in architecture and mathematics.
I have wanted to visit one of these sites ever since I saw a model of one on display in the Science Museum in London, where I worked for many years. It turned out to be even more impressive in the flesh (brick) than I’d expected, being both fascinating and sculpturally beautiful.
The bulk of the instruments are for measuring the position of the sun or other celestial bodies in the sky, and many of then look like sun dials, with a semicircular scale and angled gnomon.
Others however, including some that were devised by the Maharaja or his astronomers, are visually harder to grasp. In particular those that come in pairs: they have cut-out access routes in the gridded surfaces on which measurements are taken, with the other half of the pair having the cut-outs and measurement surfaces transposed, so between them, there is one entire surface.
The most spectacular instrument is the 27m high giant sundial (the Samrat Yantra) . Some argue that the larger the instrument, the more accurate the reading as you can have more scale divisions. But I’ve also read other sources that disagree on the basis that the edge of the gnomon’s shadow is just too fuzzy to take advantage of finer gradations.
My favourite were probably the group of twelve much smaller sundials all built at different angles, one for use in each month of the year and each labelled for a different sign of the zodiac. En mass I think they look wonderful!
The instruments were used for time measurement, tabulating star positions, predicting eclipses and weather forecasting – the arrival of the monsoon for instance. The site has a great audio guide which does its best to explain how all the instruments were used, but I really needed diagrams to fully grasp it. You can find out more in this article.
For the Lego model I’ve built one of the sundial structures. I know the approximated curve I’ve built is not correct (it should be a segment of a circle) nor in the right orientation (the angle of the gnomon should be at right angles to the plane of the curve), but hey, it’s only Lego and the best I could do in the circumstances.