by Gurbir Singh
Chapter Two
From Vedic Astronomy to Modern Observatories
C ivilisations throughout human history, both nomadic and settled, have understood the utility of astronomy. It is a prerequisite not only to understanding the concepts of the year and time of the day but also for determining geographical positions on Earth. Referring to the life and death importance of astronomy to marine navigation, Indian historian Rajesh Kochhar asserts that the institutionalisation of modern astronomy was not for the “love of the stars but the fear of death.”[66] Throughout its long history, India has had a tradition in science, albeit frequently interwoven with superstition, astrology and mysticism.[67] Preoccupation with understanding the real world was one reason why civilisation took root in India.
Hints of a science-based society in India can be found at the beginning of the Vedic period (a 1000-year period of Indian history beginning in 1500 BC when the oldest Indian scriptures, the Vedas, were composed). The Vedic communities observed and recorded the celestial motions of the Moon, planets and the Sun, and mapped the night sky into 27 nakshatras, hinting at the central role of science at the beginning of the Vedic Period. The tradition of science in India can be traced even further back to the organised societies of the Indus Valley Civilisation, also known as the Harappa Culture that flourished in India and predates the ancient civilisations in Egypt and Iraq).[68] Archaeological evidence of planned cities with streets, drains and tiled flooring suggests that precision measurement instruments and sophisticated building techniques were practised as long ago as 8000 years.
A 7-m high iron pillar stands close to the Qutab Minar in New Delhi, the capital of India. It was forged during the late 4th century BC and weighs over 6 tonnes (6000 kg). Constructed from 99.7% wrought iron, it remains rust free. Stunning statues carved in iron, copper and bronze using the lost-wax process is evidence of advanced metallurgical techniques developed in early India. History provides many examples where a scientific advance is made, forgotten and remade centuries later. The most celebrated example, perhaps, is the Antikythera mechanism discovered in 1901. This clockwork astronomical computer was originally constructed in Greece in about 100 BC. The techniques and technology needed to produce it were rediscovered in Europe around the 15th century.
In the 4th century BC, the astronomy of the Greek’s based on mathematics, precision measurements and systematic observations came to India with Alexander the Great’s (356 BC–323 BC). This Greek structured approach, however, could not uproot the entrenched culture of astrology that had persisted in India for centuries. Observational astronomy served only to support the existing ancient traditions rather than ushering in a new way of thinking shaped by the scientific method. Over the next few centuries, Indian scientists continued to engage in understanding the natural world through the language of science albeit still steeped in ancient (and non-scientific) Indian rituals and traditions.[69]
Figure 2‑1 Jantar Mantar in Jaipur. Credit McKay Savage
In the 6th century AD, long before Nicolaus Copernicus (1473–1543), Aryabhata (476–550) in India had proposed a heliocentric system. He also wrote about trigonometry, algebra and astronomy. Even though most of his writings did not survive, Aryabhata is credited with introducing the concept of zero, calculating the value of pi (π) and establishing the idea of the Earth turning on its axis daily and revolving around the Sun annually; he also provided a new explanation for lunar and solar eclipses. Aryabhata is a celebrated figure in India, so much so that Indian Space Research Organisation (ISRO) in 1975 named its first satellite, Aryabhata.[70]
Another Indian mathematician and astronomer Bhaskara (600-680) formalised and recorded Aryabhata’s work. Bhaskara is known for three of his writings, two cover astronomy in verse and one is a commentary on Aryabhata’s original work did not survive. Within a century, Bhaskara recorded and progressed Aryabhata’s contributions. He took Aryabhata’s concept of zero and implemented it as a recognisable circular symbol and established for the first time the positional (units, tens, hundreds, etc.) system familiar today. Until then, numbers were represented by words or allegories rather than numeric characters. Bhaskara developed Aryabhata’s work on trigonometry, fractions and lunar and solar eclipses.
Before the telescope was invented, celestial objects were observed with the naked eye and their positions, brightness and patterns in the sky, which changed over time, were recorded. In the 18th century, a Rajput prince and senior general of the Mughal Empire Raja Jai Singh (1688–1743) built a series of large static masonry buildings called Jantar Mantar to function as astronomical instruments, such as the astrolabe that can measure and predict the position of the Sun, Moon and stars. A total of five were built at sprawling sites in Jaipur, Delhi, Varanasi, Mathura and Ujjain, but only two (Jaipur and New Delhi) remain today. Between them, the instruments could measure the time of local noon, longest and shortest days of the year, time of the day and angular positions of stars and the Sun. His goal was to duplicate and improve the star catalogue of 944 stars developed in the 15th century by the Ulugh Beg Observatory, which was situated in modern Mongolia.
While the contributions to science, mathematics and astronomy from the Middle East (Iraq, Syria and Egypt) are well established, those from Central Asia are less familiar. Ulugh Beg Observatory was an advanced centre for astronomy in the 15th century. Despite his larger instruments, Raja Jai Singh was unable to match the accuracy of the measurements recorded by Ulugh Beg two centuries earlier,[71] Now these elegant structures are more a visitor attraction than precision instruments for a scientific investigation.
Colonialism and Renaissance
The European Renaissance (14th–17th centuries) and the Age of Enlightenment (17th–18th centuries) in Europe coincided with the colonial period in India. The British inadvertently provided a conduit for transferring the advances and discoveries of the European Renaissance in arts and science to India. Following the defeat of Tipu Sultan, innovations in rocketry flowed in the opposite direction.
Figure 2‑2 Transit of Mercury Recorded by Jeremiah Shakerley from Surat. 3 November 1651. Credit Indian Institute of Astrophysics
The transfer of science between societies has been a constant feature of human civilisation and continues today. The 15th-century invention of the printing press in Germany was timely and facilitated the prompt communication of ideas, inventions and technologies across the disparate lands of the growing Empire. Galileo’s observations of the night sky using the newly invented telescope and William Shakespeare’s literature from the UK were brought to India by scholars and engineers, who accompanied the soldiers, merchants and traders of the British East India Company. Modern ideas about the utility of science and its potential to shape the economic prospects of an underdeveloped nation were first tested in India during the colonial period.
Galileo observed the night sky using the telescope for the first time in 1609. Four decades later the first astronomical observation using a telescope was made from Surat on India’s west coast. Jeremiah Shakerley (c1626–1655), an employee of the British East India Company, recorded the transit[72] of Mercury on 3 November 1651. An experienced observational astronomer, Shakerley had calculated that the transit would not be visible from Europe. It is not known if that was the reason for his arrival in India, but he was probably the second person in history to witness a transit of Mercury. The first was probably Pierre Gassendi (1592–1655), who observed it from Paris in 1631.[73] During the transit, the planet’s silhouette would have been seen as a small dot moving slowly across the face of the Sun over a period of about three hours. Shakerley is also credited with making the first telescopic observation of a comet that was visible from India in 1652.[74]
From Pondicherry (now Puducherry) on India’s south-east coast, Father Jean Richaud (1633–1693), a French Jesuit priest, used a telescope on 9 December 1689 to observe Alpha Centauri. He discovered it was not one star but two.[75] This was the second ‘double star�
�� to be documented. Modern telescopes have revealed a third member in the Alpha Centauri system, Proxima Century, which at 4.2 light years is the nearest star to our solar system. Today, most stars are binary or multiple star systems. The stars of the Alpha Centauri system are the next nearest stars to the Earth after the Sun. Had Alpha Century been visible from northern Europe, this discovery of Earth’s celestial neighbour would have been made from Europe and not India.
The British in India recognised that recording accurate observations for time, meteorology and location were essential for a nation that relied on maritime power to administer an empire thousands of miles away. The observation data gathered and processed by the Royal Greenwich Observatory in London established in 1675 underpinned the British Empire's naval prowess. To secure and extend its hold over India, scientific institutions and technologies were introduced, and astronomical observatories were one of the first such institutions of science to be established in India.[76]
The Great Trigonometrical Survey
With Tipu Sultan’s defeat, the British East India Company acquired the vast Kingdom of Mysore. It then expanded its control from Madras (now Chennai) on the east coast to Mangalore (now Mangaluru) on the west coast. Keen to quantify his conquest, Madras Governor Lord Clive approved the suggestion that a trigonometrical survey similar to those conducted in France and Britain be repeated in India. The mathematical techniques and the precision measuring instruments used to make astronomical observations could, with some modification, be used to survey the Earth. What came to be known as the GTS of India started on 6 February 1800 and lived up to its name when it was extended to the whole of India on 1 January 1818.
GTS was a monumental scientific undertaking given the vastness and complexity of the terrain. Although established a few years prior to the start of GTS, Madras Observatory found its profile elevated by the GTS as it provided training and organisational support for the survey.[77] The man appointed Surveyor General of India from 1821 to 1827, Colonel Hodgson, was an astronomer. In addition to his surveying obligations, he supervised a series of transit observations made from Calcutta (now Kolkata).[78] The Official Manual of Surveying for India was published in 1851. It was divided into five sections: (i) Geometry and trigonometry, (ii) Surveying instruments, (iii) Surveying, (iv) On native field measurement (khusrah) and (v) Practical astronomy and its application to surveying.[79]
The British East India Company and, after 1857, the British colonial government invested some of their immense wealth in promoting science, purchasing scientific equipment and sponsoring scientists, engineers and surveyors to come to India. Apart from contributing towards astronomical and scientific progress, the instruments of science generated wealth from the discovery of coal in Raniganj, petroleum in Assam and gold in Tipu’s former stronghold of Mysore. Railways and ports were developed to facilitate the transport of this wealth out of India. Scientific literacy spread through India following the first GTS and then spread further and faster thanks to the advent of the railways.
Madras Observatory
The Madras Observatory formally came into being on 19 May 1790 when the directors of British East India Company accepted an offer from William Petrie (1784–1816) to nationalise the observatory he had personally established and operated since 1787 with two 3-inch (7.6 cm) achromatic telescopes, two astronomical clocks and a transit instrument. The first official astronomer of the observatory was John Goldingham (1767–1849), who calculated the time difference between London and Madras to be 5 hours and 21 minutes. This was subsequently used to establish Indian Standard Time of GMT +5:30 that is still used today.
The British East India Company was preoccupied with its expansionist ambitions and particularly with defeating the troublesome Tipu Sultan in southern India. Its first significant foothold in India was in Madras (now Chennai), so establishing the first observatory there was a natural outcome. The motivations for establishing the Madras Observatory were to (i) survey the territories it already had, (ii) increase revenue earnings, (iii) ensure the safety of sea passage and (iv) learn about the geography of the country for future expansion.[80]
Figure 2‑3 The Madras Observatory 1838. Credit Indian Institute of Astrophysics
The British East India Company recorded its primary aim for the Madras Observatory as “promoting knowledge in astronomy, geography and navigation in India.”[81] Following Tipu Sultan’s defeat in 1799 and the start of the Great Trigonometrical Survey (GTS) in 1800, the activities of the Madras Observatory accelerated.
The Madras Catalogue
Thomas Glanville Taylor (1804–1848), whose father had been the first assistant at the Royal Greenwich Observatory in London since 1805, arrived at the Madras Observatory in 1830. By 1831, he had installed two astronomical instruments, a 4-foot (121 cm) mural circle and a transit telescope, both having lens 3.25 inches (8.9 cm) in diameter, optically both were substantially powerful instruments. With these instruments, he was able to record precisely the positions of the Sun, Moon, planets and stars. The transit instrument, a telescope mounted such that it can only move up and down and not sideways, allowed him to measure precisely when stars in the night sky crossed his local meridian (passed directly overhead).[82] The data collected helped to explain the geometry of planetary orbits and through parallax detect the proper motion of stars.[83] With the support of four ‘native assistants’ over several years, Taylor produced what came to be known as the Madras Catalogue of 11,015 stars, which the Astronomer Royal Sir George Airy (1801–1892) described as the “greatest catalogue of modern times”[84].
Taylor recorded and published his works in many volumes over several years in Madras. In his book, Astronomical Observations Made at the Honourable East India Company’s Observatory at Madras, herecords in detail the challenges of his undertaking. A violent storm on 30 October 1836 blew away the top of his observatory, and torrential rain and high winds further damaged his instruments; it took three months to fully recover from this devastation. This book was the second edition of his fourth volume recording the observations made during 1836–37. In the preface, he explains why the second edition was necessary. The ship carrying the printed copies had sunk with “nearly the whole of the copies of the former edition having been lost in the wreck of the Duke of Northumberland.” [85]
Discovery of Helium
In 1814, Joseph Ritter von Fraunhofer (1787–1826) developed the first spectroscope in Germany. A spectroscope was a new powerful analytical tool that could determine the chemicals in a flame just by looking at the light from it. This was true for light from the stars and planets too, but that light was extremely faint. Long exposure photography made it possible to accumulate the faint light from telescopic observations, something that the human eye could not do. Long exposure photographs revealed details that could not have otherwise been seen revealing stars, structures in galaxies and details in planetary atmospheres, that were otherwise too faint. In short, astrophotography made the invisible visible. Combining astrophotography and spectroscopy made it possible to investigate the chemistry of celestial objects.
On 18 August 1868, a spectrum of the Sun was recorded in Guntur in South India during a total eclipse. Many European teams visited India specifically for this event. Often, new scientific discoveries follow the invention of new scientific tools. The introduction of spectroscopy in astronomy held the prospect of something equally profound.[86] The 1868 spectrum of the Sun led to the discovery of helium in the atmosphere of the Sun.
Figure 2‑4 Solar Eclipse. Turkey. 29 March 2006. Credit Toni May
Norman Robert Pogson (1829–1891) observed the same eclipse from Masulipatam (Madras was not in the ground-track of the eclipse). Red tape delayed the publication of his spectroscopic observations, thus denying him the credit of discovering helium. Pierre-Jules-César Janssen (1824–1907), who observed from Guntur, published his work with Joseph Norman Lockyer (1836–1920) first. So, Janssen and Lockyer were credited with the discovery instead.[87]Three ye
ars later, spectroscopy was used on the much fainter (than the Sun) light from a distant star, star Argus. The first recorded spectrum of a star in India was made at the Madras Observatory on the eve of the total solar eclipse of 1871.[88]
The Earth-Sun Distance
Though planetary transits are arguably not as visually spectacular as a total solar eclipse when the Moon completely obscures the Sun, they are unique and have the potential to generate new scientific knowledge. Only Venus and Mercury have their orbits between the Earth and the Sun, and planetary transits occur when one of these comes directly in between the Earth and the Sun and their silhouette appears on the disc of the Sun. The first record of the transit of Venus was made on 24 November 1639 by Jeremiah Horrocks (1618–1641) and William Crabtree (1610–1644) observing in Salford and Preston, about 31 miles (50 km) apart in the north-west of England.
Celestial mechanics determine that pairs of Venus transits separated by eight years repeat every 130 years. Johannes Kepler (1571–1630) had calculated that one would occur in 1631 and accurately predicted that it would not be visible from Europe.[89] The next in the sequence in 1639. Following his observation of the transit in 1639, Horrocks was able to estimate the size of Venus and the Earth-Sun distance to about 50% accuracy. The transit of Venus occurred again in 1761 and 1769, but only the 1761 instance was visible from India. In 1761, the British East India Company was not as well established in India as it would be in the later decades, but instructions for observing the transit from India were published.[90]