Scanning the Skies in Jaipur Trivia Quiz

Answer: Calculating machine

Although the complex at Jaipur is the most famous, there are other collections of structures that function as ways of measuring astronomical data with the naked eye, such as the one to be found in New Delhi. Technically, the term applies to the equinoctial sundial, of which more anon, but it is usually applied to the entire complex.

The early state records of Jaipur use the word Jantra or Yantra, the original word for an instrument (with Mantar being the word for measuring). The altered form of Jantar is recorded since the start of the 19th century.

Answer: Maharaja Sawai Jai Singh II

The incorrect options were all notable Mughal rulers in the subcontinent. Jai Singh II ascended the throne of Amber (now Jaipur) at the age of eleven, on the death of his father. The Mughal emperor at the time, impressed by his intelligence, bestowed the title Sawai on him.

This title literally means 'a quarter over one', suggesting that he had more than a single person's worth of intelligence. In 1719, Jai Singh was inspired by listening to a court debate over how to determine the most auspicious date for the commencement of a planned journey to turn his attention to astronomy.

He subsequently constructed five separate complexes of astronomical instruments, finishing the last of them by 1735. The purpose was to compile accurate astronomical tables, which would allow accurate predictions of the movements of celestial objects.

The largest complex was constructed at his newly built capital city of Jainagara, now known as Jaipur. The complex built in Mathura has disappeared, and the one in New Delhi is no longer functional, but those at Jaipur, Varanasi and Uijan are still fully functional observatories.

Answer: It is the gnomon of the world's largest sundial.

With a name meaning Great King of Instruments, this is the world's largest sundial, with a gnomon (the pointer whose shadow indicates the time) reaching a height of 27 metres. The stairs along its hypotenuse allow access to the chhatri at the apex, from which announcements about upcoming events such as eclipses were made.

The hypotenuse is inclined at 26 degrees, corresponding to the latitude of Jaipur, and is lined up with the earth's axis of rotation (so it point to the celestial north). The semicircular ramps on each side are marked to show the time when the shadow lies at each position. Because of its size, it is accurate to within two seconds! If you stand and watch it, you will see it move about a millimetre a second, or 6cm (a bit more than 2 inches) in a minute. Of course, it indicates local time, and needs to be corrected to give standard time, since Jaipur is not at the centre of its time zone.

Answer: Vernal and autumnal equinoxes

This is an example of the careful attention to detail and demand for high precision behind this site. On the equinoxes, the sun does not cast shadows appropriately on the Samrat Yantra near the middle of the day, and this smaller, and less accurate, building can be used. Less accurate means that it only measures within a minute, rather than 2 seconds. And since it is only really needed for a few hours a year, its very existence pays tribute to Jai Singh's attention to detail.

I was unable to locate a picture of the Dakshin Bhitti Yantra that could be used for this question. It is a two-story building with a curved scale along one wall, framed by two flights of stairs allowing access to the top of the structure. The image for the question shows part of the curved scale on the Samrat Yantra. The one on the Dakshin Bhitti Yantra lies flush with the wall, rather than being freestanding.

Answer: The latitude at which it is located

The dial has to be parallel to the earth's equator for optimal accuracy, so it is inclined at (approximately) 26 degrees. There is a sense in which the season matters, although it is not what determines the angle of inclination. The Narivalaya Yantra is actually composed of two dials (mounted back-to-back), one with the central rod pointing towards the South Pole, and one with the rod pointing at the North Pole.

In the winter, the one facing south is used, with the one facing north being the summer instrument.

At local noon, the shadow points straight down along the circular face. In the morning, it points to the west of vertical, and in the afternoon to the east. While it is very accurate for determining local noon, its accuracy decreases as the sun moves to be closer to the horizon.

Answer: For both day time and night time observations

During the day, the plate casts a shadow on the curved base of the bowl, while at night an observer standing in the bowl can use it to sight celestial objects and locate them by noting where the observer is standing. (This is when the hole in the centre comes into play.) This instrument is especially useful because the markings you can see on it represent celestial observations made with two different recording systems: both azimuth-altitude measurements (based on local measurements) and an equatorial coordinate system relating the positions in more universal terms. This is another monumental instrument - the diameter of its rim is 5.3 metres (17.5 feet). Observers can walk around inside it using the steps and platforms that have been built in for that purpose.

The design of this instrument, which includes a second one with the inscribed areas and the observational areas exactly reversed so that you can stand in whichever one is most suitable and not get in the way of your own measurement, is considered to be one of the triumphs of Shah Jai Singh. The pair of hemispheres are located near each other, so it is a relatively simple matter to walk from one to the next as the observed object's position changes.

Answer: True

The axis of the ring (perpendicular to the line between the two hinge points) is aligned so that it points to the North Celestial Pole. In the centre is a hole to which an observation tube is attached when it is in use. As you look through the tube, you can record how you move it from this rest position until you see the desired object. Movement of the entire ring down towards the horizon, measured in degrees, gives you the declination of the observation; movement in a clockwise or anticlockwise direction around the axis gives you the ascension, which is usually recorded as the right ascension, the number of degrees of counterclockwise rotation needed. Markings on the ring allow this to be quickly read.

Answer: False

This is yet another device for measuring the location of celestial objects in the night sky. Unlike the Chakra Yantra, which is fixed on pivots, this circle is suspended so that it swings freely. The observer once again attaches an observation tube to the point where the two arms cross, and moves it until the target object can be seen.

The amount of horizontal and vertical rotation made is then recorded. Readings on this instrument are usually made in terms of altitude (distance of rotation up from the horizon) and azimuth (clockwise rotation from due north).

Answer: All three are the same.

This is another example of a device for which the two halves are mirror images. The floor of each of the two cylinders consists of alternating sectors (at chest height) with markings for making measurements, and gaps in which the observer can walk. When the observation falls in the gap of one instrument, the observer can just walk next door to the other cylinder.

The observer lines up the top of the cylinder, the object under observation, and the spot on the floor or wall where those two points project.

In the day, this is easily seen by the shadow; at night a sighting guide is used. Markings on the floor and walls provide the most accurate measurements for locations near the point where they meet, corresponding to an angle of elevation of 45 degrees.

At this point, readings are accurate to within 1 minute of arc (one-sixtieth of a degree); near the base of the pillar or the top of the wall that is reduced to about 1 degree.

Answer: Constellations of the Zodiac

Sidereal time is measured according to the way in which the stars seem to move as the earth completes its annual orbit around the sun. The path its orbit traces is called the ecliptic, and that is traditionally divided into twelve equal zones spanning 30 degrees of the sky, each associated with a constellation located there (or nearby - the names are not nearly as accurate as the measurements). Each of the twelve sundials has its gnomon aligned with the centre of one of these zones. Once you have used the other instruments on the site to determine which constellation is the one in which the sun is currently located, you can choose the appropriate one for your use.

The shadow then tells you the sun's location in sidereal coordinates. This 12-piece instrument was apparently used primarily for horoscopes (rashi).