In New Delhi, just behind famous Imperial Hotel, is a quiet and beautifully kept garden which contains six large, strange masonry structures. It is dominated by what appears to be a steep staircase to nowhere; even stranger are two cylindrical structures with central pillars and radial marble spokes. The visitor might be forgiven for thinking he had strayed into an exhibition of avant-garde sculpture, although these futuristic shapes have a solidity and a clean, functional beauty foreign to most contemporary art.
This a jantar mantar, or astronomical observatory. The structures are gigantic instruments for calculating the positions of heavenly bodies. It was built in 1724 by Jai Singh, Maharaja of Jaipur, at the request of the Moghul emperor Muhammad Shah.
Jai Singh was born in 1688, a year after the publication of Newton's Principia, and in 1700, when he was 11 years old, he succeeded his father as ruler of the small Rajasthani state of Amber. By the time of his death, he had increased his domains until they included most of what is now the modern province of Rajasthan. Although of course Hindu, he ruled as deputy for a number of Moghul emperors, the most important of whom was Muhammad Shah, who came to the throne in 1719.
Very little is known of Jai Singh's early years, of when or how he developed an interest in mathematics and astronomy. It is said that at the age of 13 he invented an ingenious method of raising water to irrigate the hanging gardens of Amber, the extraordinary fortress-palace in the mountains overlooking Jaipur.
Jai Singh was an accomplished scholar of both Sanskrit and Persian at an early age, and thus had direct access to both the Indian and the Islamic scientific traditions. He sponsored a number of translations into San -skrit of Arabic astronomical and mathematical works, and his library, the Pothi Khana in the beautiful City Palace of Jaipur, still contains 18 manuscripts of Islamic scientific works.
It is fascinating that Jai Singh's assistant, Samrat Jagan-nath, was commissioned to translate the fundamental work of Greek astronomy, Ptolemy's Mathematike Syn-taxis, into Sanskrit some 1500 years after the death of the author. Ptolemy lived in the middle of the second century of our era, and the Mathematike Syntaxis had been translated into Arabic in 827, under the name al-Majisti, or The Greatest - whence Almagest, the name the work was known by in the Lajjn Middle Ages. It was from the Arabic translation, probably in one of its revised forms, that Jagannath prepared the Sanskrit version.
Ptolemy's Almagest is perhaps the longest-lived and most influential textbook ever written. For almost a millennium and a half it dominated scholars' minds, and it was not until the 16th and 17th centuries that men like Tycho Brahe, Copernicus, Galileo and Sir Isaac Newton finally demolished the Ptolemaic view of the universe.
For the Almagest contained a fundamental error: Ptolemy believed that the earth was stationary and that the sun revolved around it. In order to make observation fit this mistaken model, Ptolemy had to resort to ingenious and complicated calculations. It is a tribute to his inventiveness that the result provided a perfectly adequate explanation of observed planetary movement -even though the basic premise was entirely mistaken.
The great Arab and Persian astronomers of the Middle Ages never seriously questioned the Ptolemaic model of the universe. Their efforts were concentrated on refining details of the system, elaborating Ptolemy's brilliant exposition of trigonometry and, particularly, in the design and fabrication of new and increasingly sensitive observational instruments.
It was this tradition of practical astronomy that interested Jai Singh. Books VII and VIII of the Almagest's 12 contain a list of the fixed stars of the northern and southern hemispheres, arranged by constellation. The latitude, longitude and magnitude, or apparent brightness, of each star is given. Altogether, Ptolemy catalogued 1022 stars - all, of course, visible with the naked eye, for the telescope lay some 1500 years in the future.
At various times, Islamic scholars sought to bring Ptolemy's star catalogue up to date, as well as to fix the positions of the stars more accurately as they refined new astronomical instruments. This was first done by the scholars of Gondeshapur, not far from Baghdad, in AD 800. An observatory was founded in Baghdad itself in 819 - perhaps the first true observatory since Alexandria - and a new star catalogue prepared. In the year 1000, a star catalogue was prepared at the observatory in Cairo for the Fatimid caliph al-Hakim, and in 1118 an astronomer named al-Khazini prepared another at the observatory of Nishapur, in today's Iran, which had been founded in 1074.
Similar efforts were made in Islamic Spain, where in 1080 the "Toledan Tables" were produced, to be followed in 1252 by the "Alfonsine Tables," prepared in Seville for Alfonso the Wise by Arab astronomers.
Seven years after the compilation of the Alfonsine Tables, far away to the east, in a small town in Azerbaijan called Maragha, a new and important star catalogue was prepared. Maragha was the preferred residence of Hulagu Khan, the grandson of Genghis, who in 1258 had sacked Baghdad and put an end to the Abbasid caliphate. Here Hulagu - who, perhaps surprisingly, was very interested in science - established an important observatory and placed it under the directorship of one of the leading scientists of the time, Nasir al-Din al-Tusi. His "Il-Khanid Tables," as they are called, were the most accurate so far produced. The instruments used at the Maragha observatory were described in detail by a Syrian instrument maker named Mu'ayyad al-Din al-'Urdi, so we know more about Maragha than any other observatory in the Islamic world.
It was also via Maragha that a knowledge of the Greco-Arab tradition of astronomy reached China, for China, like the eastern Islamic world, was under Mongol domination in the 13th century, and perhaps for the first time ideas flowed from the Islamic world to China rather than the reverse. An astronomer from Maragha was sent to China, and the dynastic chronicles of the Yuan record how he designed an instrument for observing the heavens and erected it on the Great Wall.
But the star catalogue that particularly interested Jai Singh was the most famous of all - the "Tables of Ulugh Beg." Ulugh Beg was the ruler of Turkestan and Transoxiana in the 15th century. In 1428 he built an observatory at Samarkand that was considered by his contemporaries one of the wonders of the world (See Aramco World , January-February 1990). The catalogue of 1018 fixed stars prepared under Ulugh Beg's auspices was the most accurate and detailed yet produced, and Jai Singh decided to bring it up to date, for in the 297 hijri years that separated the two rulers the observed position of the "fixed" stars had changed.
At first Jai Singh experimented with the small brass instruments normally used by Islamic astronomers, but he decided that their size was in itself a source of observational error. In the preface to his tables, which he named Zij Muhammad Shahi, in honor of his patron, he explains:
To carry out the order he had received... he constructed several of the instruments of an observatory like that of Samarkand, according to the books of the Muslims, such as a brass armillary sphere two meters [6.5 feet] in diameter, a two-ringed astrolabe [and others]. ...But he found that these brass instruments were not sufficiently accurate, because of their small size, the lack of division into minutes, the wearing of their axes, the displacement of their centers and the shifting of the planes of the instruments. He concluded that the observations of the ancients, men like Hipparchus and Ptolemy, were inaccurate because of this.
Some of the brass instruments used by Jai Singh still survive and are on display in the City Palace Museum in Jaipur and in the museum at Kotah. To counteract the errors which he believed to be the result of using relatively small instruments, Jai Singh decided to build very large stationary instruments in stone, with the graduations cut into the marble or limestone. These are the instruments that can still be seen at the jantar mantar in Delhi.
Jai Singh was not the first astronomer to attribute observational error to the small size of his instruments. The famous 11th-century historian and astronomer al-Biruni said, "It is impossible to fix the parts of the greatest circle by means of the smallest circle. I refer to the small-ness of the instruments of observation in comparison with the vastness of the bodies which are to be observed." And another Muslim astronomer wrote, "The larger the instrument, the more correct the observation."
Jai Singh claims to have invented three of the most imposing instruments in the jantar mantar himself, and this may well be true. It is also possible, however, that he had descriptions of similar instruments used in Ulugh Beg's observatory. Still speaking of himself in the third person, Singh says:
Therefore he built [in Delhi]... instruments he invented himself, such as the Jai Prakas, Ram Yantra and Samrat Yantra...with attention to the rules of geometry and taking care to adjust to the meridian and to the latitude of the place, and taking care in measuring and siting them so that inaccuracies from the shaking of the circles and wearing of the axes and displacement of their centers and the inequality in the marking of the minutes might be eliminated. Thus an accurate method of constructing an observatory was established and the difference between the calculated and observed positions of the fixed stars and planets through observation of their mean motions was eliminated.
The Samrat Yantra (Prince of Instruments) is the most immediately striking structure in the observatory, the staircase that seems to lead nowhere. In fact, it is nothing more than a gigantic equinoctial dial, or sundial. It consists of a stone gnomon, as the pointer of a sundial is called, whose hypotenuse is parallel to the earth's axis. On either side is a quadrant of a circle parallel to the plane of the equator, graduated in hours, minutes and degrees. When the sun rises, its shadow falls on the highesf point of the western quadrant and then descends until noon. The shadow then falls at the point where the eastern quadrant meets the gnomon, rises up that quadrant during the afternoon and reaches its highest point at sundown. The hour can be read off the quadrant where the shadow meets the marked gradations. A scale of tangents on the gnomon itself allows the sun's declination to be found.
The two circular structures, open at the top, with central pillars, slatted sides and radial marble spokes, are the Ram Yantra. They are complementary, and together form a single instrument, the gaps in the sides of one corresponding to the slats in the side of the other. They were used to find the altitude and azimuth of the sun, stars and planets. The distance from the top of the wall to the graduated floor is equal to the distance from the bottom of the wall to the central pillar. The top of the wall is counted as zero degrees; 45 degrees is marked by the juncture of wall and floor. At sunrise the shadow of the pillar falls on the top of the wall, indicating that the altitude of the sun is zero degrees. As morning wears on, the shadow moves down the side of the wall; the sun's altitude is 45 degrees when the shadow meets the juncture of the wall and the floor. When it is 90 degrees - vertical -there is no shadow at all. The azimuth, or horizontal angle, of the sun may be found by bisecting the thick shadow of the pillar as it falls on the gradations on the radial spokes of the floor. The altitude and azimuth of other heavenly bodies may be read by manipulating a thread tied to the central pillar.
The last two major instruments at the Delhi observatory are the Jai Prakas and the Misra Yantra. The Jai Prakas was used to find the position of the sun by means of the shadow cast by two intersecting wires on a concave hemisphere. The hemisphere was marked with altitude and azimuth circles, tropics and declination circles.
Misra Yantra means "mixed instrument," so-called because it combines different devices in one. The complex contains a smaller version of a sundial, a graduated semicircle for meridian altitudes, and a horizontal quadrant.
Jai Singh first became aware of advances in European astronomy while he was building the Delhi jantar mantar. As he himself says in the preface of the Zij Muhammad Shahi:
After seven years had been spent in this work, information was received that at about this time observatories had been built in Europe and that learned men in that country were carrying out this important work... and that they were constantly striving to determine with accuracy the subtleties of this science.
He obtained - perhaps from a Jesuit missionary - a copy of the French astronomer de la Hire's Tabulae Astro-nomicae, printed in 1702 and, at a slightly later date, those of the British astronomer John Flamsteed, a colleague of Newton and Halley. Flamsteed's Historia Coelestis Britan-nica lists the positions of almost 3000 stars, for Flamsteed was able to make use of the telescope, which seems to have been unknown to Jai Singh.
Flamsteed's great work also reprinted three earlier European star catalogues, so with that of Ulugh Beg, Jai Singh had a long series of observations available for purposes of comparison. Jai Singh claimed to have found an error of half a degree in the position of the moon in Flamsteed, as well as a small error in the times of solar and lunar eclipses. He attributed these errors to European use of small instruments.
Jai Singh's own copy of Flamsteed can still be seen in the Pothi Khana at Jaipur, and he may well have owned other European works. Yet he nowhere mentions the telescope - invented by Galileo in 1609 - or the fact that more than 200 years had passed since the Ptolemaic system had been dealt its death blow by Copernicus.
Yet Jai Singh sent at least one emissary to the king of Portugal, requesting him to send an astronomer to aid him; the king did send a medical man named Da Silva who had some knowledge of astronomy. It may be that Jai Singh neglected the stirring advances that had taken place in Europe because almost all the learned Europeans he came into contact with were Jesuit missionaries, who - theoretically, at least - would have considered Copernicus, Tycho Brahe and Galileo to be heretics. The works of Galileo, after all, were not removed from the church's Index of Prohibited Books until well into the 19th century. In 1727, Jai Singh began the construction of a new city, Jaipur, to replace Amber as capital; it became one of the most unusual cities in India, as well as one of the most beautiful. He built an observatory in Jaipur as well, much larger than that in Delhi and with many more instruments: the Samrat Yantra in Jaipur is over 27meters (almost 90 feet) high and some 44 meters (147 feet) long. The observatory also includes some fixed metal instruments, including two disc astrolabes two meters (6.5 feet) in diameter. Jai Singh built three other observatories as well, at Ujjain, Benares, and Muttra, so that readings in one place could be checked against readings in another.
His aims as an astronomer were relatively modest, despite the size and beauty of the instruments he constructed. He wished to bring Ulugh Beg's tables up to date and if possible make them more accurate; he wished to provide almanac makers with more accurate information; and finally, he wished to be able to tell time more accurately. The Jaipur observatory was used to establish the correct time right up to 1944.
But Jai Singh was probably mistaken in his belief that large instruments produced finer readings. He knew that Ulugh Beg had used a quadrant some 55 meters (180 feet) high to prepare his tables, and was influenced by the views of Arab astronomers on the subject. Yet he seems to have been unaware that advances in European astronomy had been made by recognizing the inevitability of error and seeking to minimize it through the use of the vernier, micrometer and telescopic sight.
Jai Singh came at the very end of a tradition - the Greco-Arab - that reached back to second-century Alexandria and beyond. The study of the instruments he used and a knowledge of their limitations contributes a great deal to the understanding of pre-telescopic astronomy and the problems faced by medieval astronomers. His jantar mantar at Delhi, and its counterparts at Jaipur, Ujjain and Benares, hint at what the famous observatories of Baghdad and Maragha must have looked like in their prime.
Bibliophile and historian Paul Lunde studied at London University's School of Oriental and African Studies, and now lives in Spain.