History of Indian Astronomy

Ancient Indians' interest in astronomy was an extension of their religious preoccupations and inasmuch, astronomy and mathematics ran parallel. Both were faithful to the needs of objectivity and subjectivity. Astronomy began as mere wonder at what was observed in the heavens above, grew into a systematic observation and speculation, hence forward into scientific inquiry and interpretation, finally emerging as a sophisticated discipline. Mystical interpretations of the movement of stars and planets developed into astrological science, and astronomy grew into a major factor in the intellectual pursuits of different cultural periods.

The chief sources of astronomy-related information are the Vedic texts, Jain literature, and the siddhantas (texts), as also the endeavours in Kerala. Some seals of the Indus Valley period are believed to yield information of the knowledge available to those early settlers, as also the orientation of certain constructions clearly governed by such considerations. An interesting aspect is the Jantar Mantar observatories built by Sawai Jai Singh of Jaipur. There are 5 such structures for measuring time and for astronomy-related calculations, at New Delhi, Varanasi, Jaipur, Mathura and Ujjain. These eighteenth century astrolabes are important for both scientific and architectural reasons.

Sawai Jai Singh, in his determination to provide accurate astrological tables, ordered these gigantic structures of stone. The Jaipur observatory includes the largest sundial in the world with a 90 feet high projecting arm (the gnomon). The measurements achieved by these Jantar Mantars were particularly impressive for their time - the astronomical table was very accurate and in some instances, better than contemporary western ones. This table was published in Persian and Sanskrit as the Zij Muhammad Shahi. The time was and is calculated by a study of the shadows cast by the central straight walls on to the curved walls beyond. The weather forecasts and other information provided by these sundials are very much in use at present, for religious and practical purposes.

THE VEDAS AS SOURCE

The four Vedas comprise the Samhitas - texts of prayers and hymns, charms, invocations and sacrificial formulae. The Rig Veda is the Book of Devotional Verse, the Yajur Veda is the Book of Sacrificial Formulae, the Sama Veda is the Book of Chants, and the Atharva Veda is the book of Mysticotherapeutic Priestcraft. Their composition precedes their arrangement into the four Samhitas by a long period of oral transmission.

Rig Veda and Atharva Veda hymns point to the observance of a lunar year. The Moon itself was regarded as the 'maker of months' - masakrt. Many indications are present as to the awareness of the autumn equinox - references to Aditi (this corresponds to Pollux, longitude 113°). Daksha (Vega longitude 284°), Rudra (Betelgeuse, longitude 88°) and Rohini (Aedebaran, longitude 69°). The changing longitudes mentioned are a consequence of the precession of the equinoxes. These details are useful for another reason: they reveal the date of composition. Thus, allowing for 72 years per degree (plus, allowance for error) the years should be 6200 BC, 5400 BC, 4350 BC and 3070 BC respectively. Hymn 1.164 of the Rig Veda composed by the sage Dirghatamas refers to a wheel of time with a year 0f 360 lunar days and twelve lunar months. The year mentioned in the hymn begins with the Autumn star Agni (Alcyon, longitude 59°5), corresponding to the year circa 2350 BC. (The numbering of the hymns demonstrates use of the decimal system).

Yajur Veda and Atharva Veda reveal a definite calendrical awareness - many sacrifices, including the Gavam Ayana, are of different lengths of time based on the daily cycle of the Sun. For reasons of ritual, the day was divided into 3,4,5 or 15 equal divisions, each with a different name. Apart from naming twenty seven stars beginning with Krttika, these Vedas mention five planets and name two of them - Juipter (Brihaspati) and Venus (Vena).

The Taittriya Brahmana speaks highly of nakshatravidya (nakshatra= stars, vidya= knowledge) and states clearly the existence of scholars of this science.

JAIN LITERATURE AS SOURCE

The Ardha-Magadhi Prakrit texts are composed of the fragments and oral traditions of the original Jain texts known as Punva. This recasting was the effort of the Svetambara sect, and this body of work consists of forty five or fifty books. The basic texts are:

a) Angas: these concern rituals, legends, and doctrines. Of the twelve Angas, two - Sthananga and Bhagavatisutra - relate to astronomy and mathematics. The others are - Acaranga, Sutrakrtanga, Samavayanga, Jnatrdharmakatha, Upasakadasa, Antakrtadasa, Anuttera-aupapa-tikadasa, Prasna-Vyakarana, Vipakasutra and Drstivada.

b) Upangas - these too are twelve in number, of which Suryaprajnapati, Candraprajnapati and the Seventh Section of Jamudvipaprajnapati concern themselves with astronomy. The second section of Jambudvipaprajnapati discusses Time, the concept ranging from asankhyata ('inscrutable infinitesimal Time') to sirsaprahelika i.e. millions of years.

c) Prakirnakas - these are miscellaneous texts, ten in number.

d) Chedasutras - these nine books state the rules that govern monastic life, including jurisprudence.

e) Mulasutras - of the four Mulasutras - Uttaradhyayana, Avasyaka, Dasavaikalika and Pinda-inryukti - the first contains some facts on astronomy and mathematics.

The Culikasutra of two parts - Nandisutra and Anuyogadvarasutra- is a treatise on astronomy and mathematics.

Jain post-canonical literature is represented by work such as Tattvarthadhigama Sutra by Umasvati (AD 185-219) on astronomy and cosmology; the 7000-verse Trilokaprajnapati by Yati Vrsabha (AD 473-609) of which chapter 27 is on astronomy; Jyotisakarandaka by Padaliptacharya (based on the Suryaprajnapati) that contains the total of Jain views and observations on astronomy; Karananuyoga or Ganitanuyoga of the Digambara sect, a comprehensive text on Jain astronomy.

The Centre of the Universe

Mount Meru was regarded as the central axis of the Earth, the latter seen as a motionless planet. These two, along with the constellations, planets, continents, rivers, seas and mountains constitute Jambudvipa (literally, 'rose-apple land'). Certainly, this had a metaphysical aspect as well- Mount Meru is the subtle inner essence that generates everything (or Reality). Awareness of the subjective reality of all creation (that everything is connected) is sometimes expressed through the diagram of the Jambuvriksha, i.e. the world tree. The cosmic diagrams of Jain literature depict Mount Meru at the centre, and the outermost limit illustrates the twelve months, the planetary cycles and the movements of the Sun the Moon. The Polar Star is depicted as being directly above Mount Meru.

In addition to these works, there were the books on astronomical yantras (devices). Mahendra Suri's (AD 1348) Yantraraja was followed by the Ustaralayayantra by Meghalaya (circa AD 1500) which discusses the use and construction of the astrolabe (an instrument to determine the altitude of planets and stars). These two are the major works in this field.

THE SIDDHANTAS AS SOURCE

Of the eighteen early siddhantas written by Pitamaha, Surya, Vyasa, Atri, Vasistha, Kasyapa, Parasara, Narada, Garga, Manu, Marici, Lomasa (Romaka), Angiras, Bhrgu, Paulisa, Cyavana, Yavana, Saunaka, only five survive as extracts. Panchasiddhanta by Varahamihira (composed in AD 578) includes the siddhantas of Surya, Vasistha, Pitamaha, Paulisa and Romaka.

The later siddhantas represent a considerable advance in astronomy- they were far more precise and calculations were accurate and easier than in the past.

The Aryabhatiya (AD 499) of Aryabhata the First discussed spherical astronomy in addition to calculations for planetary positions and their mean. Solar and lunar eclipses were elaborated upon, as also the fact that the Earth's shadow was responsible for the phases of the Moon, that the Earth rotated on its axis, and the Moon revolved round the Earth.

Bhaskara the First's works- Mahabhaskariya and Laghubhaskariya- were commentaries on the Aryabhatiya. He calculated complete revolutions performed by a planet using Aryabhata's rule. Bhaskara's equation y=ax-C/b is a variation of Aryabhata's x=by+c/a. In Bhaskara's equation, a=bhajya (revolution number of planets), b=hara (divisor or civil days in a yuga), c=agra (residue of the revolution of the planets), x=gunkara (complete revolutions of a planet, i.e. ahargana) and y=phala (complete revolutions performed by a planet).

ASTRONOMY IN KERALA

Aryabhata the First's system was followed by astronomers in Kerala (a state of southern India) who in AD 683 met in Tirunavay to launch the Parahita system of computation. This new method was an amendment of the former. The major texts were Grahacaranibandhana and Mahamarganibandhana by Haridatta. However, over the centuries it was found that observations did not correlate to the results as calculated by the Parihata system. Thus, in 1431, Parmesvara's (1360-1455) Drk system gained ascendance.

During this period, a host of other literary works on astronomy were written based on the Parihita and Drk systems. Known as Karana literature, this included:

a) Karanaratna by Devacarya. The eight chapters deal with calculations for the longitudes of the Sun, Moon, and the planets, eclipses, gnomon shadow (the shadow on a sundial cast by a stationary arm), helical visibility, planetary conjunctions and the rising of the Moon.

b) Vakyakarana (AD 1300) and Drkharana by Jyesthadeva (AD 1500- 1610).

c) Karanasara by Sankara Variyar (AD 1500-60).

d) Karanamrta by Citrabhanu (circa 1530).

e) Sadratnamala by Sankara Varman (1800-38).

Vakyas are the mnemonics used by both systems to generate different astronomical tables. For instance, the work Candravakyas of Vararuci yields the two hundred and forty eight daily longitudes of the Moon for nine anomalistic months. Other vakyas provide, for instance, the 3031 daily lunar longitudes for 110 anomalistic months.

The Aganita-grahacara by Madhava is replete with information on the Moon, the longitudes of planets stretching over many years, and planetary motions. All of it is neatly organized into tables.

Computing the shadow of the Moon aided the calculation of time and planetary positions. Many works were composed on this topic, the major ones being: Candracchyaganita I by Paramesvara, followed by Candracchayaganita II by Nilakantha, and Candracchayaganita III and IV that remain anonymous. Other works include Chayaslaka by Acyuta Pisarati, and three anonymous texts Candracchayanayanopavah, Chayaganita (four different volumes), and Suryacchayadiganita (two different works).

There were eight important texts on astronomical rationale:

a) Lagnaprokarana by Madhava (1360 - 1440) discussing the computation of the ascendant.

b) Grahanayayadipaka by Paramesvara that dealt with the computation of eclipses.

c) Yuktibhasa by Jyesthadeva on astronomy and mathematics.

d) Rasigolasphutaniti by Acyuta Pisarati that provided calculations for measuring planetary longitudes on the ecliptic.

e) Nyayaratna by Putumana Somayaji.

f) Ganitayuktayah on astronomical theory.

g) Jyotirmimamsa by Nilakantha, composed in 1504. This work focussed on the vital role of observation in astronomy, as well as the need to correct parameters regularly on the basis of the eclipses, Sun, Moon and the planets.

h) Grahapariksakarana, also by Nilakantha, that provided details of methods of practical astronomy.

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