Indian Journal of History of Science, Vol, 45, no.2, June 2010, pp. 287-297

Rajesh Kochhar

Abstract

Rahu and Katu were deployed as planetary deities in the sixth century CE immediately after the mathematical theory of eclipses was propounded by Aryabhata. Their literary credentials however go back to early Vedic times. Here our aim is to examine, in a joint mythological and astronomical-astrological (“astronomological”) context, how the textual meanings of Rahu and Ketu have evolved with time. There are clear stages in their evolutionary histories, which must be borne in mind while interpreting early references.

The legend of Rahu shows signs of internal development. Successor to the Rgvedic Svarbhanu, Rahu as eclipse-causing demon was reduced to a body-less head so that the swallowed sun or moon had an escape route. Rahu’s identification with the lunar ascending node represents an attempt to connect new scientific developments with traditional beliefs. Ketu, in contrast, was a dictionary word used to denote a variety of related phenomenon especially comets. The promotion of the head-less body as a demon represents expansion of mythology in the light of new scientific developments. Ketu was now given an additional entirely new role, creating avoidable confusion. Significantly, Ketu’s iconography represents efforts at reconciling its two disparate roles.

Key words: mathematical theory of eclipses, astrology, Vedic mythology, planetary deities, Buddhist mythology, astronomical omens, ritual

Ancient Indian perception of the moving cosmic environment two millennia ago was bipolar. Orbits of the seven geocentric planets (graha) by virtue of their predictability represented cosmic order, while phenomena like meteors, comets and eclipses which did not fit into any pattern were classified as utpata, portent or calamity. This world view is preserved in a Buddhist Sanskrit text, Sardulakarnavadana, the legend contained in which is known to have been translated in an abridged form into Chinese in 265 CE (Vaidya 199,p.xi) . As the 5^th century CE came to a close, the status of eclipses was modified.

Mathematical theory of eclipses was propounded in India in 499CE by Aryabhata (born 476 CE) in his influential Siddhantic treatise simply known as Aryabhatiyam (See Ohashi 2009 for a recent review). According to this theory, solar and lunar eclipses occur when the moon is at either of its orbital nodes. These theoretical points move in a direction opposite to that of the planets and complete an orbit in the rather short period of 18.6 years. This development was immediately taken note of in astrological literature, which classified the two nodes as planets, implying that they were now amenable to mathematics. Since they were hypothetical they were dubbed shadow planets. The 6^th century CE text Brihajjataka (2.2-3) by Varahamihira (died 587 CE) includes Rahu and Ketu in the list of planets, and even gives their synonyms: Tamas, Agu and Asura for Rahu; and Shikhi for Ketu (Rao 1986, p.76), which however never gained currency. The two nodes are 180 degrees apart so that specifying one fixes the other. It would thus have sufficed to include just one of them. Both were listed no doubt to bring the planetary number up to nine which was considered sacred.

If new words had been coined to designate the two nodes, matter would have rested there. But both Rahu and Ketu are terms of Vedic vintage. The term Rahu had previously been used as a proper noun and exclusively in connection with eclipse so that its deployment represents an attempt at integrating new scientific developments with ancient tradition. On the other hand Ketu was merely a common noun employed variously but never in association with eclipse. Here then was an old term which was given an entirely new identity, representing expansion of mythology in the light of new scientific developments.

It is not uncommon to see even earlier references to Rahu and Ketu being interpreted in terms of their later status. This is unfortunate, because it distorts the history of the evolution of “astronomological” thought. The new coinage is advisedly used in preference to the extant terms astronomical and astrological to avoid backdating the present differentiation into earlier times when they would have been essentially seen as one. Our aim is to investigate how the textual meanings of the terms Rahu and Ketu have evolved with time. We must keep in mind some notable features of the available source material. Most texts remained open for a long time and were contributed to by generations of authors. There is no reason to expect or demand internal self- consistency from them. The texts were often composed in metrical poetry and were meant for a select audience. Very often the meaning assigned to a particular word depends on the context in which it is used.

An important source of information on ancient India is the Mahabharata which was expanded over a long period of time to include matter that went beyond the description of the Bharata battle which it had originally set out to describe. The astronomical content of the Mahabharata is consistent with Vedic astronomy in that it marks sky positions with the help of bright stars or star groups known as naksatra. The Mahabharata is not familiar with the twelve zodiacal signs which make their appearance in post-Mauryan India in about the first century BCE at Baudha Gaya where they are depicted on the railing pillars (Kane 1975, p. 598). Given the size and the nature of the contents of the Mahabharata it is reasonable to assume that if zodiacal signs had been introduced into India when the Mahabharata text was still open they would have found their way into it. We thus conclude that the Mahabharata text had been closed by about 1^st century BCE (Kochhar 2000, p.56). This is an important datum. At one place the Mahabharata (Vanaparva 188. 87-88) does say that “when the moon, the sun and Jupiter in Tisya come together in one rasi, krta age will begin”. The term rasi is used here in the general sense of a portion of sky, not in the precise sense of a zodiacal sign.

The Mahabharata does not make any reference to the week days either. There is no unanimity on the epoch when they were introduced into India. Varahamihira, already referred to, in his other works , Pancasiddhantika and Brihatsamhita, mentions week days while quoting authorities who had lived much earlier . From this it has been inferred that week days were introduced into India in the first century CE(Kane 1975, pp. 680-1). A more plausible case has been built by Markel (1991) to suggest that the week made its appearance in India only in forth century CE.

Vedic Rahu and Ketu

The Rgveda does not know of Rahu. Rgveda (5.40:5-9) describes how Svarbhanu, son of an asura, pierced the sun “through and through with darkness”. The eclipse caused great distress among observers: “All creatures looked like one who is bewildered, who knoweth not the place where he is standing”. The sun himself appealed to Atri: “Let not the oppressor with this dread, through anger, swallow me up, for I am thine, O Atri”. In response, “By his fourth sacred prayer Atri discovered Surya concealed in gloom that stayed his function”. “The Brahmana Atri, as he set the press-stones, serving the Gods with praise and adoration, established in the heavens the eye of Surya, and caused Svarbhanu’s magic arts to vanish. The Atris found the Sun again, him whom Svarbhanu of the brood of Asuras had pierced with gloom. This none besides had the power to do.” (Griffith 1896, p. 255) .The Atris were prominent contributors to the Rgveda. The whole of the fifth mandala is authored by them. The passage quoted above is mentioned and embellished at a number of places in the Vedic literature :Tandya Brahmana (4.5.2; 4.6.13; 6.6.8; 14.11. 14-15; 23.16.2), Gopatha Brahmana (8.19), Satapatha Brahmana (5.3.2.2), and Sankhayana Brahmana (24.3) ( Dikshit 1896, Vol.1, p.58; Kane 1975, pp. 241-242). What the Atris probably did was to chant mantras while the eclipse lasted. The Rgvedic description is significant. An eclipse was seen as the demon’s work in disrupting the cosmic order. Propitiation was needed to restore that order.

Dikshit (1896, Vol. 1, p. 57) while translating a passage from the Rgveda renders Svarbhanu as Rahu and goes on to give its meaning as the lunar ascending node. Similarly Kane (1975, p.569), while discussing a reference in the Maitrayani Upanisad, equates Rahu and Ketu with the ascending and descending node respectively. Svarbhanu’s career as an asura did not last long. It is not clear when and how Svarbhanu made way for Rahu, who appears for the first time, and as the sun’s enemy, in Atharvaveda (19, 9-10). Chandogya Upanisad (8.13) makes an interesting analogy: The “soul that has acquired true knowledge is said to shake off the body after casting off all evil” like “the moon becoming free from the mouth of Rahu” (Kane 1975, p.569).The Pali Buddhist sources refer to the moon and the sun freeing themselves from the clutches of Rahu by invoking Buddha’s name (Candima Sutta, Samyutta-nikaya 2.9; Suriya Sutta, Samyutta-nikaya 2.10).

Mahabharata (Bhismaparva 13.39-45) uses both Svarbhanu and Rahu as interchangeable names. Rahu is a graha, 12000 yojanas in diameter, bigger than both the moon (11000 yojanas) and the sun (10000 yojanas). Rahu had to be bigger than the sun and the moon so that it could grab them. Note that the term graha here carries the sense of a grabber and not that of a body in orbit. In course of time, the name Svarbhanu came to be de-stigmatized so much so that a son of Lord Krsna was given the name (Mani 1975, p. 778).

Atharvaveda (13.16-24) employs Ketu to mean ray of light. These nine verses are taken from Rgveda (1.50.1-9) in the same order and more or less in the same form. They are also found “in one or more other Vedic texts” (Whitney 1905, Vol.2, p.722). More typically Ketu meant combination of fire and smoke. The Atharvaveda passage (19.9.10) quoted above refers to Dhumaketu as an epithet of mrtyu [death]. It either means a comet or literally as “smoke-bannered” to the smoke rising from a funeral pyre (Whitney 1905,Vol. 2, p. 914). Atharvaveda (11.10.1-2, 7) uses Ketu in the plural, as arunah ketavah [ruddy Ketus]. Here the reference seems to be to comets or meteors. Varahamihira’s Brihatsamhita, composed in 6^th century CE but containing much older material, quotes a still earlier astronomer Garga on a class of 77 comets, called Aruna, which are dark red in colour (Bhat 1981,Vol. 1, p.138).

Puranic Rahu and Ketu

If the demon Rahu devours the sun or the moon to cause an eclipse, how do they become visible again? The answer is provided by the well – known story samudramanthana (churning of ocean), described in Mahabharata, Visnupurana and elsewhere. In the story, the demon Rahu’s head is chopped off, which survives. It is the Rahu head which causes an eclipse. Since the rest of the body is missing, there is an escape route for the sun and the moon. Note that the name Rahu now belonged to the body-less head. The head-less body would remain unclaimed, till the 6^th century CE; see below. Brhatsammhita (5:1-3) while narrating this story also refers to a prevalent alternative belief that Rahu is of a serpentine form with only the head and the tail. The ancient Iranian text Bundahishn talks of goshir, an eclipse-causing serpent. It is not clear whether Varahamihira is referring to the Iranian legend or an un-recorded Indian one. Al Biruni writing in the 11^th century reserves the name Rahu for the dragon’s head and calls the tail Ketu (Sachau 1888, Vol. 2, p.234).There were some half-hearted attempts to relate eclipses to predictable phenomena. Thus it was speculated that an eclipse took place when five planets get together (Brihatsamhita 5.17)

Mahabharata (Adiparva 65. 11-12, 31) names Kasyapa as the father and Simhika as the mother of Rahu, who is at times designated Simihkeya after her. His three other real brothers are also mentioned, their given names, Sucandra, Candraharta and Candrapramardana, all being associated with moon. Kasyapa from another wife Danu had 34 named sons including one called Ketuman (not Ketu).Curiously the names Surya, Candramas and Svarbhanu figure in the list (Adiparva 65.22-26).These 34 demons are thus Rahu’s half brothers. This naming is an exrecise in meaningless creativity. This association may have an astronomical basis which does not seem to have been noted before. Varahamihira in his Brihatsamhita (3.7; 11.22) mentions a class of 33 comets known as Tamaskilakas (dark shafts), called children of Rahu. They were noticed by the 11^th century astronomer and chronicler Al-Biruni also. Described as black, and shaped like a crow or a beheaded man or a sword, or bow and arrow, they are always in the neighbourhood of the sun and the moon. It is likely that this category include sunspots (Bhat 1981, pp.25-26). An ancient authority quoted by Varahamihira on Tamaskilaka is Garga, who figures in Mahabharata also as an astronomer and advisor ( Mani 1975, p. 280). He may well have been responsible for constructing a myth about 34 half-brothers of Rahu out of the description of Tamaskilakas. It is noteworthy that from independent considerations Garga has been place at about 100 BCE (Kane 1975, p.681), the epoch we have assigned to the closure of the Mahabharata.

Inverted astronomy in Mahabharata

The Mahabharata talks about the prevalent astronomical knowledge albeit often in an inverted manner. It will be useful to inspect the context in which these references were made.

When the two rival armies stood confronting each other, and the Bharata war looked imminent, last ditch efforts were made to avert it by appealing to the ineffectual king Dhrtarastra whose villainous sons were widely held responsible for bringing things to such a pass. To convey the enormity of the sense of impending genocide, the king was told that in anticipation of the war the natural order had already broken down. The effect was heightened by the fact that the so-called eye witness account was brought to the sightless king by his own biological father. The revered Ved Vyasa tells Dhrtarastra (Bhismaparva 3.46) as follows.

“Cows are giving birth to asses; and elephants to dogs. Sons are enjoying sexual pleasures with their mothers. Idols of gods are laughing, vomiting blood, feeling sad, and falling off their pedestals on their own. Animals are being born with three horns, four eyes, five feet, two urinary organs, and two tails. Women are giving simultaneous birth to four –five girls, who immediately start singing, dancing and laughing. Trees are flowering out of season. Lotus and water-lily are blossoming on tree tops. Even koel, peacock and parrot are making fearsome sounds. There is a downpour of blood and bones from the sky.”

The imagined weirdness of the world in anticipation of the fratricidal war was extended to the skies as well. “Arundhati well known for her devotion to her husband Vasistha has left him behind. [The reference here seems to be the star pair in Ursa Major rather than to individuals.] Dawn and the dusk look like as if they are on fire. Vyasa tells Dhrtarastra that he could not make out the difference between day and night, because the sun, moon and the stars all were burning bright throughout. This is a fearsome sign. Although it was the Kartika full moon night, the moon was not visible; its luster had given way to fire.

It is in this background that even the more-reasonable sounding descriptions of celestial phenomenon should be seen. A recurring theme is the reference at various places in the Mahabharata to Rahu, as if the occurrence of an eclipse was at par with holocaust on earth. “Rahu has seized the sun” (Bhismaparva 3.11). “Rahu is approaching the sun” (Bhismaparva 141.10).”Rahu swallowed the sun most untimely” (Salyaparva 55.10). “Rahu eclipsed the sun and the moon simultaneously” (Asvamedhaparva 76. 15, 16, 18). Meteors (ulka) and earthquakes are also similarly invoked. As part of the celestial foreboding it is stated that a very dangerous Dhumaketu has overcome the naksatra Pusya. This will bring destruction to both sides. (This ill-omen appears in the 4th century CE Buddhist text Sardulakarnavadana as well; see below).

Continuing, his listing of ill omens, Ved Vyasa tells Dhrtarastra that the sveta graha (white planet) has transgressed Citra, while the parusa graha (harsh planet) has established itself between Citra and Svati (Bhismaparva 3.11, 16). The translators have exercised their own discretion in rendering these terms. Sveta graha has been left untranslated (Sathe et al. 1985, p.39) or equated with Ketu (Ganguli 1884-1896, Book 6, p.12). Parusa graha has been identified with Rahu by one translator ( Ganguli 1884-1896, Book 6, p.12) and with Ketu by ANOTHER (Sathe et al. 1985, p.39).. The arbitrariness is obvious. As we have argued it would be anachronistic to associate Rahu and Ketu with a planet in pre-Varahamihira times.

Greek astronomical elements made their documented appearance in India in 149 CE when a Greek astro-text was translated into Sanskrit by Yavanesvara. It was versified in 269CE by Sphujidhvaja under the title Yavanajataka (Pingree, p. 1959). The versification was a significant development, because it signifies assimilation of Greco-Babylonian elements into Indian tradition. And yet, Vedic astronomical tradition remained extant even after the introduction of Yavana texts, as can be seen from passages in Sardulakarnavadana, already referred to. “Irrespective of the naksatra, when the sun or the moon is seized by Rahu, the king along with his subjects comes to pain.” “Irrespective of the naksatra when Ketu enters the moon, the neighbouring enemy king gets the upper hand.” “When Dhumaketu establishes itself in the Pusya naksatra, then defeat in enemy’s assault from all four directions is guaranteed” (Vaidya 1999, p. 374, couplets 462,463, 466). As we have already noted, Dhumaketu in Pusya as a bad omen is mentioned in the Mahabharata also. It is significant that Ketu and Dhumaketu are listed separately and along with Rahu under utpata.

Once the mathematical theory of eclipse was propounded, Rahu ceased to be an utpata; its predictability however did not remove the fear associated with it. On the other hand, Ketu as comet continued to be an utpata. Brihatsamhita assigns separate chapters to a discussion on eclipses under the heading Rahu and on comets under Ketu. Brihatsamhita does not mention Ketu in the context of eclipse. As mentioned earlier, it is Varahamihira’s other text Brihajjataka which twins Ketu with Rahu as the eclipse-causing shadow planets, introducing the concept of navagraha. Ketu was now given a brand new identity; the torso which had been lying lifeless after the detachment of the Rahu head was now resurrected and named Ketu.

We have argued that inclusion of the demon Rahu in the list of mathematically tractable planets took place after 499CE. Support for this conclusion comes from iconographic data. The “ first surviving depiction of Rahu occurs in a relief of the ‘Churning of the Ocean’ carved over the façade of the doorway of cave-temple number nineteen at Udayagiri in the Vidisha district of Madhya Pradesh, which can be dated to ca. A.D.430-450. Earliest known representations of Rahu as a member of the planetary deities are those on two stone lintels, 100cm by 20cm, originally from the villages of Nachna and Kuthara in the Panna district in the Bundelkhand region of Madhya Pradesh, most likely sculpted during the reign of the Uccakalpa king Jayanatha (r. ca. A.D.490-510)” ( Markel 1990, pp.11-13). If the assigned dates are correct, it is remarkable that Rahu’s planetization occurred within a decade of Aryabhata’s theory. Ketu as a planetary deity appears in about 600 CE or a little later, in Uttar Pradesh. In the eastern state of Orissa, Ketu was not counted in until the tenth century, which thus had only eight grahas till then (Markel 1990, p.21). One wonders whether it was from Orissa that Rahu as Yahu travelled to Burma as one of the eight nats (spirits).

Astronomical literature employs the term Rahu in connection with eclipse but in a number of ways. Aryabhata does not use either Rahu or Ketu; he and following him many others refer to a node as pata. Brahmagupta (b.598CE) in his long career displays signs of intellectual evolution. Taking a position contrary to Aryabhata, he in his Brahmasphutasiddhanta, prepared in 628 CE, expresses his faith in the demon Rahu as the cause of eclipse . Al Biruni noted this (Sachau 1888,Vol. 2, p.110). His later text, Khandakhadyaka (665 CE), however, calculates eclipses in a matter-of-fact way employing the technical term pata and without naming Rahu or Ketu (Chatterjee 1970, pp. 80-85).

The 689 CE astronomical handbook Karanaratna by Devacarya (Shukla 1979) uses Rahu to denote the eclipse shadow (2.2) as well as the ascending node (e.g.1.15). Significantly, at one place (1.13) the latter is called Rahumukha (Rahu head). A tersely written basic astronomical text will have no reason to mention Ketu. As comet, meteor or the like Ketu lay outside the scope of theory while as descending node it would be redundant once the ascending node Rahu or pata was mentioned.

In later Iranian (and Arabic) mythology the ascending node Rahu and the descending node Ketu become the head and the tail of the dragon Al –Djawzahr. Ketu as comet is not forgotten; he figures as al-Kayd (Hartner 1965). Rahu and Ketu as part of mathematical astronomy were introduced into China during the Tang dynasty (618-907CE), but with modified meaning. While Rahu was retained in the sense of the lunar ascending node, Ketu was used as a designation for lunar apogee (Niu 1995)

The imagery and iconography of Rahu and Ketu have evolved over time, with the latter having been more difficult to conceptualize. While Rahu has been well-defined since the days of the samudramanthana story, Ketu had in the sixth century CE the eclipse role thrust upon him in addition to the cometary ( and not the other way round as Neugebauer (1957, p.211) suggests).

The tradition of eclipse calculation has continued uninterrupted till relatively recent times. A copper plate inscription tells us about the grant of a village by the Kalachuri king Ratnadeva II to an astronomer , Jagannatha by name, for correctly predicting the lunar eclipse of 1128CE. He knew two Siddhantas and succeeded where other astronomers in the court failed. Hence the reward ( Mirashi 1933-34,p.161).Seven centuries later, a Pondicherry-based traditional astronomer calculated for the benefit of John Warren the lunar eclipse of 1825 May 31-June 1, with the help of shells, placed on the ground, and from tables memorized “by means of certain artificial words and syllables”. The results were remarkably accurate for the time. There was an error of +4 minutes for the beginning, -23 minutes for the middle and -52 minutes for the end (Neugebauer 1983, p.436). Traditional almanacs still use old algorithms for their planetary position calculations, but have taken to using modern methods for calculating eclipses as a concession to the greater time consciousness of the present times.

To sum up, the terms Rahu and Ketu have been continuously in use since the early Vedic times, but their meaning has not remained static. Rahu was an eclipse-causing demon whose name was confined to the severed head in the samudramanthana story. In the sixth century CE, Rahu was identified with the ascending node of lunar orbit and designated the eighth planet.

From the earliest time till the sixth century CE, Ketu was not a proper noun but a dictionary word used to denote phenomena like comets and meteors. This meaning continued later as well. But in the sixth century CE, Ketu was made into a proper noun by identifying it with the descending node of the lunar orbit and designating it the ninth planet. The headless body of the demon left behind from the samudramanthana days was retrospectively named Ketu. This evolutionary sequence needs to be kept in mind while interpreting textual references. More specifically, identification of Rahu or Ketu with a planet in a text prior to Varahamihira would be an exercise in anachronism.

I thank Yukio Ohashi, K.T.S. Sarao, B.V. Subbarayappa, K. Ramaubramaniam and Michio Yano for help and useful conversations.

References

(To help place an author’s work in context, date of original publication is cited in the text. For convenience, date of translation or reprint, mostly facsimile, is added.)

Bhat, M. Ramakrishna (1981) Varahamihira’s Brihat Samhita (Delhi: Motilal Banarasidass).

Chatterjee, Bina (1970) The Khandakhadyaka of Brahmagupta with the commentary of Bhattotpla, Vol. I. ( Delhi: Motilal Banarasidass).

Dikshit, Sankar Balakrishna (1896) History of Indian Astronomy (English translation by R.V. Vaidya, Pt I,1968; Pt II, 1981. New Delhi: India Meteorological Department).

Ganguli, Kisari Mohan (1884-1896) Mahabharata of Krishna-Dvaipayana Vyasa ( on-line)

Griffith, Ralph T. H. (1896 ) The Hymns of the Rgveda ( Reprint, Delhi : Motilal Banarasidass, 1973).

Hartner, W. (1965) “ Al-Djawzahar”. In :Encyclopedia of Islam,Vol.2 ( Leiden: Brill), pp.501-502.

Kane, Pandurang Vaman. (1975) History of Dharmasastra, Vol. 5 (Poona: Bhandarkar Oriental Research Institute).

Kochhar, Rajesh (2000) The Vedic People (Hyderabad: Orient Longman).

Mani, Vettam (1975) Puranic Encyclopaedia (Delhi: Motilal Banarasidass).

Ohashi, Yukio (2009) “The mathematical and observational astronomy in traditional India”. In: Science in India, Vol. 13, Pt.8 (ed. J.V. Narlikar) (New Delhi: Viva Books), pp 1-88.

Markel, Stephen (1991) “The genesis of the Indian planetary deities”. East and West, Vol. 41. pp. 173-188)

Markel, Stephen (1990): “The Imagery and Iconographic Development of the Indian Planetary Deities Rahu and Ketu”. South Asian Studies, 6:9-26.

Mirashi, V.V. (1933-34) Epigraphia India, Vol. XXII, 159-165.

Neugebauer, Otto (1957) “Notes on Al-Kaid”. J. Amer. Oriental Soc., 77, 211-215.

Neugebauer, Otto (1983) Astronomy and History : Selected Essays ( New York : Springer-Verlag).

Rao , Bangalore Suryanarain (1986) Varahamihira’s Brihat Jataka ( Delhi : Motilal Banarasidass, Reprint 2008).

Sachau, Edward C. (1888) AlBeruni’s India, ( 2 vols reprinted as one , Delhi : Atlantic Publishers)

Sathe, Shriram: Deshmukh, Vijaya; and Joshi Prabhakar ( 1983) Bhartiya Yuddha: Astronomical References ( Pune : Shri Babasaheb Apte Smarak Samiti).

Shukla, Kripa Shankar (1979) Karana-Ratna of Devacarya ( Lucknow : Lucknow University).

Vaidya, P. K. (ed.) (1999) Divyavadana ( Darbhanga: Mithila Institute).

Whitney, William Dwight (1905) Atharva-veda-samhita, 2 vols. (Cambridge, USA: Harvard University).

Yano, Michio (2003)”Calendars, astronomy and astrology” .Blackwell Companion to Hinduism (ed.:Cavin Flood)( Oxford: Blackwell)

Invited review presented at International Astronomical Union /UNESCO Symposium 260 : The Role of Astronomy in Society and Culture, UNESCO Paris, 19-23 January 2009.

Rajesh Kochhar

CSIR Emeritus Scientist, IISER:

Indian Institute of Science Education and Research,

Sector 26, Chandigarh 160019, India

[email protected]

Indian astronomical tradition has been characterized by antiquity, continuity and interaction with the outside world. Here we focus on some selected aspects of astronomy-culture interactions;

         How knowledge about astronomical universe was  used to regulate human conduct in the joint Indo-Iranian tradition.

         How the religious and the ritualistic tradition influenced the astronomical pursuits.

         How astronomical knowledge in turn modified the extant mythology.

         We also raise an important general question : when  and how does tradition gets frozen and emerge as touch-me-not

Human beings are born astronomers. Ever since they learnt to walk upright they have looked at the sky and wondered. The sky has remained the same but not its meaning.

We can distinguish between three phases in the history of humankind’s relationship with its cosmic environment: (i) propitiatory phase; (ii) negotiatory phase; and the current (iii) expository phase (this probably needs a better name). Each of these phases leads to and coexists with the next. 

To begin with, sky was home to divinities who were to be feared and propitiated. As time progressed, human beings felt more secure and became intellectually more alert. Earlier awe made way for curiosity.  Skies were now scanned for discovering patterns in the behaviour of the divinities. The knowledge so gained   was put to practical use and employed to establish a negotiatory relationship with the celestial bodies. 

The third phase ,  properly speaking, began exactly four centuries ago with Galileo. The cosmic environment was now be subjected to scientific scrutiny with a view to discovering and testing laws of nature. Earlier astronomy had measured angles; now it could talk of distances.  The sky now acquired depth literally as well as figuratively. 

There is an interesting correlation between the world geopolitics and our view of the cosmos, which does not seem to have been noticed before. For a very long time, the model universe had a centre. The pride of place first belonged to the earth and then to the sun. Even when galaxies were discovered our Galaxy was believed to be the largest. It is in relatively recent times, in the post- World War II era, that the universe has truly become egalitarian. Interestingly, this cosmic scheme has been mimicked on the earth as well. When the universe was centric, the earth, or parts thereof, also had a power centre, be it local or on a larger scale. 

The Copernican principle now applies, at least in principle, on  the earth as well.  Is this a coincidence?  Or is it  that our perception of the cosmos influences the scheme of things on the earth   just as this perception itself is fashioned by the situation on earth? 

My concern today is to discuss the interplay between astronomy and culture in general in the Indian context. Much of the discussion belongs to the negotiatory phase described above.  I have advisedly used culture in the plural in the title. This is not so much to describe the scope of this review as to draw attention to its limitations.

For a number of reasons, discussed in a different context elsewhere, most of the world attention on India’s past has focused on Sanskrit texts and the associated culture (Kochhar 2008a; Kochhar 2008b).

 We have no clues whatever to the astronomical knowledge prevalent during the various phases of the  vast Harappan archaeological tradition the roots of which go back to the very beginning of agriculture and animal husbandry in what is now Baluchistan (Kochhar2000). Also the astronomical knowledge residing in the fields rather than in the archives  and especially belonging to communities officially termed scheduled tribes needs to be examined in depth. New scholarship must go beyond the Sanskrit India. 

Source material

A discussion that involves ancient India must take note of the nature and limitations of the source material available. Scripts (Kharoshthi, Brahmi) were introduced into India about 3rd century BCE or some what earlier for writing Prakrit languages derived from Sanskrit.  Script for Sanskrit itself, the language of Hindu scriptures, was adopted much later.  Writing material came from plants or trees and had a short life. Paper was not introduced into India till about 8^th century CE. The Vedic texts were in any case forbidden to be written.  

Ancient Indian intellectual tradition has been oral. Texts were in the custody of specialist caste groups who memorized them and transmitted them to the next generation by word of mouth. The extant texts would have been supplemented with explanatory “notes” to serve an immediate purpose. What was not considered worth preserving was lost for ever. Also, it is not possible to assign firm dates to any early event or development. It is therefore not possible to construct a connected account about any aspect of early India. 

We must cull relevant information from a variety of literary sources. Sanskrit provides texts at three levels. (i) The most important of these is the Vedic corpus, comprising priestly books composed by a large number of authors over a long period of time, which could be as much as two thousand years, say from 1700 BCE to zero CE (Kochhar 2000).The importance of the Vedic texts lies in the fact that scrupulous care was taken to preserve them in their original form. They are thus truly representative of the time of their composition even if that time is largely indeterminable.

The pride of place in the Vedic corpus goes to the oldest and the stand-alone text, Rigveda, containing about ten thousand stanzas. According to Kochhar (2000) it was composed over a period extending say from 1700BCE to 900BCE, although its earliest portions probably contain memories of still earlier time. (Some other texts, though closed later, may contain much  older matter. ) 

There are a few stray astronomical references in the Rigveda, but for our purposes the more useful is the Yajurveda which is a manual for actual performance of ritual. It contains some observational material, such as bright  stars visible on the journey of the moon ( the nakshatras)  as also reference to  the colures.

There is a solitary Vedic text, Vedanga Jyotisha, devoted exclusively to astronomy. It is the least understood of the whole corpus, partly because it was overtaken by developments. The oldest portions could be as old as 1400 BCE. Interestingly it deals only with the movements of the sun and the moon. Zodiacal signs and week days and other pre-Ptolemy elements would be introduced into India about 100 BCE, as part of interaction with the post-Alexandrian Greco-Babylonian world; see below. (Western scholarship especially during the colonial period tended to deny antiquity or originality to ancient India. As a backlash, many researchers have tended  to    unduly stretch  the chronology backwards.)

 The Vedic texts constitute the heritage of Hinduism. The youngest texts, like Manava Dharma Shastra, or Manu Smriti, which could be as recent as zero CE plus minus, represent transition to Hinduism proper. 

(ii) The texts associated with Hinduism as practiced are the Puranas and the two epics, Ramayana and Mahabharata. They were narrated to the public at large and used to be recast to suit the prevailing requirements of the narrators as well as the listeners.  Interestingly only additions were made, no deletions. 

(iii) In addition there are scientific corpus dealing with astronomy ( as also with health care, that is Ayurveda) which  underwent deletion as well as addition.

So far we have listed sources in Sanskrit ( the term is used loosely to include pre-Sanskrit). (iv)  In addition valuable information comes from Buddhist and Jain sources. The former include material from outside India. 

Cosmic order and human ethics 

The eternity around us has stood in sharp contrast to the short time-span of the human beings themselves. This chasm has been sought to be bridged by denying death finality. The “burial cultures” have postulated the physical rising of the dead, while the “cremation cultures” have distinguished between the body and the soul, and spoken of the indestructibility of the latter. 

There is a beautiful concept linking the divine with the human that goes back to the joint Indo-Iranian times. Called rta in the Rgveda and arta (or asa) in the Avesta, it refers to the cosmic order, not in the sense of impersonal laws of nature as ascertained from the outside, but as an example of righteous cosmic conduct which the humans should emulate. 

The sun, moon and other geocentric planets dutifully and predictably orbit around the earth. (Their predictability was a source of comfort, in contrast to the  sudden ill-omened appearance of comets, meteors, etc.) The laws regulating the behaviour of these divinities are inbuilt into the system. But similar regulation of human conduct can come only from an explicit prescription of a code of ethical conduct. Emphasis on rta / arta is far more pronounced in the Avesta than Rigveda. 

To bring the terrestrial and the celestial closer together the Vedic people assigned the attributes of one to the other. Planets return to their place in the sky; so do seasons on the earth. But human beings are born and die. In analogy with the planets, human beings should also have continuity. To achieve this, the concept of reincarnation was introduced. But in a certain sense planets are condemned to a life of incessant motion. An endless cycle of birth and death would be a punishment rather than a boon. Therefore the concept of what we may call truncated eternity was introduced, under the name moksha or nirvana, whereby a soul is liberated from the constraints of future birth. 

The cyclic time

Far more important were the human attributes assigned to the gods. The concept of age, birth and death was introduced for the cosmos as a whole, and a cosmic chronology in the form of the yuga system was constructed by suitably scaling up the human calendar. The eternity of the planetary orbits was generalized to set up an oscillating universe without beginning or end.  

For the mathematically oriented brave hearts, the technical details are explained in Appendix I. Here we may notice some important features of the scheme.  

In the Vedic period, a year was taken to comprise 12 months and 360 days. Multiply these two numbers to get 360×12=4320. Now, suffix this number with the requisite number of zeroes to produce long structured time-spans. The basic unit is a mahayuga (mega-age): 

              1   mahayuga=4.32 million years.

A still bigger time-span, Brahma’s “twelve-hour” day (or night), or a kalpa, is defined as equal to 1000 mahayugas:

1  Brahma’s day=4.32 billion years. 

Ancient Indians were probably the only people talking of such large numbers and of the endlessness of the universe. These numbers have been noticed by modern cosmologists in their textbooks as the cosmological timescales indeed turn out to be of the order of billions of years. 

A maha-yuga, in turn, is composed of four ages or yugas :  Satya or Krta;  Treta;   Dvapara; and   Kali. The scheme has some interesting attributes: 

ü                Virtue decreases down the ages in the ratio 4:3:2:1.

ü                Duration of the individual ages also decreases in the same ratio.

ü                Kaliyuga is thus the shortest.

ü                We are currently in the kaliyuga. 

The scheme must have  been found very attractive because it was used in entirely different contexts with the same terminology. These long ages were employed in astronomy. The terminology of the four yugas was also employed by the Puranas to periodize   political history going back about 100 generations. This has caused much contemporary confusion.

          The scheme was formulated in the kaliyuga itself. It is significant that the present age was postulated to be the kaliyuga. We are now in the worst of times. Things can only improve. Imagine, if we had been placed in any of the earlier yugas, things would have had to deteriorate further before they could improve. It is thus an inherently optimistic scheme. During the movement against the British rule in India, the dark kaliyuga’a making way for satyayuga was repeatedly  invoked  to enhance nationalist consciousness. 

 A pioneering name in the  systematization of the post-Vedic astronomy  was Aryabhata (b. 476 CE). Indian mathematical astronomy , which we may call Siddhantic (since the astronomical texts were called Siddhanta, proven in the end), focused on calculating geo-centric planetary orbits and especially the lunar and solar eclipses. 

From 6^th century CE till Kepler’s time , Indian astronomers were probably the only ones who could calculate eclipses with any degree of accuracy. The unbroken tradition was alive till as recently as 19^th century. A Tamil astronomer computed for John Warren , a French astronomer in the service of British East India Company, the lunar eclipse of 1825 May 31-June 1 with an error of +4 minutes for the beginning,-23 minutes for the middle, and -52 minutes for the end ( Neugebauer 1983:435).

An Indian astronomer adjusted his parameters and obtained satisfactory match between the calculated sky and the actual sky. This match  would  disappear in a few centuries. A brilliant astronomer then appeared on the scene ,  and reworked the mathematics. Remarkably although the physical  goal was the same different astronomers ended up setting up and solving different equations. Mathematics was a tool for planetary calculations. There are very few full-time mathematicians in the Indian tradition ( Kochhar 1993). 

Sacred texts influence science

Use of early astronomical data in the ritual profoundly influenced the later course of astronomical developments. The yuga system with its nomenclature was borrowed by the astronomers. Thus the Surya Siddhanta would say that there were 146,568 revolutions of Saturn in a mahayuga, implying an orbital period of 29.4743 years. 

Interestingly,  at places Aryabhata   chose to  deviate from the Vedic yuga scheme. He split a mahayuga into four equal parts. Also , he  set his kalpa equal to 1008 mahayugas (instead of the Vedic 1000). Since 1008 is divisible by seven, all  kalpas,  each 4.32 billion years apart   will begin on the same day of the week. Some far sight indeed ! 

Like the  (( divine) Rigveda  astronomical texts were composed in verse, so that an astronomer had to be a Sanskrit poet first. Constraints of metre forced astronomers to use synonyms and take recourse to allusions. This introduced ambiguity at places. More importantly only   conclusions were preserved  and not the arguments leading to them. Generally speaking there was a tendency to present astronomical results as revealed knowledge rather than deduced.

Aryabhata believed in the spin of the earth and said so in his work.  This however never became a part of the mainstream. He was severally criticized for this by his “adversaries”. Even later astronomers belonging to his  own school felt so embarrassed that they tried to change a  word here and there in his work to convey the impression that the great master like everybody else took the earth  to be non-spinning.  Today we give great credit to Aryabhata for his belief in earth’s spin. But it is important to keep in mind that our source of knowledge is his critics who were putting Aryabhata’s lapses on record. (As a belated compensation Aryabhata’s glorifiers now falsely credit him with belief in heliocentrism.)

 As an analogy, we may note that we know about the deeds of  revolutionaries  fighting for India’s freedom from the charge sheets filed against them by the colonial government. 

If astronomy had followed a prose tradition (as was the case with post-Vedic Upanishads) some later scholars could have revived and expanded on Aryabhata’s hypothesis. 

Indian astronomers were not aware of the precession of equinoxes. A creative astronomer would adjust his parameters so that his computed planetary orbits matched the observations. With the passage of time the  computed sky would differ from the actual. This ar necessitated the arrival of  a new mathematician – astronomer on the scene.

 Ancient India astronomical effort was society oriented rather than sky oriented. Its aim was to prepare almanacs pinpointing auspicious times for social and religious purposes. It is certain that most if not all students who learnt astronomy did so to become practising astrologers. 

The ancient astronomical texts were unambiguously attributed to their named authors. But at the same time their contents were incorporated into traditionally-named texts that were passed off as having been revealed to the chosen ones (e.g. Surya Siddhanta). This pretension to divine connection no doubt increased the astrological market value                                                                                                                                                                                                  of the texts and ensured funding of astronomical activity by the society. 

(It is noteworthy that Buddha was against astrology. As long as Buddhism held sway astronomy went in decline. It is only on resurgence of Hinduism that astronomy revived. By the time Buddhism was exported, astrology had become part of it.) 

Aryabhata’s influential and pioneering work  closes with the stanza : “This work , Aryabhatiya by name,is the same as  the ancient Swayambhuva [i.e. revealed by Swayambh] and as such it is true for all times. One who imitates it or finds fault with it shall lose his  good deeds and longevity “. It has been argued-and with justification-that a man of  Aryabhata’s   known scientific approach could not have made such a pompous and intimidating statement. While this argument exonerates Aryabhata, it does indict his                           later-day followers , and tells us about the  atmosphere in which such a statement could be made and attributed to Aryabhata himself (Kochhar 1993).

Old astronomical knowledge  has remained a living tradition even if its role is not so obvious now. Spring and autumn equinoxes as well as winter solstice ( but not the summer solstice) are still celebrated as religious festivals. (Thus  spring and autumn equinoxes are honoured by nine-day celebration each, called navaratri. Makar samkranti, the sun’s ingress into Capricorn , on about 14 January,  is nominally celebrated as northward turning of the sun . Jupiter’s 12-year orbital period is commemorated by the Kumbh festival, marking Jupiter’s computed ingress into Aquarius.) 

Traditional  almanacs in  current use still use old prescriptions. They have accumulated an error of 23 days due to precession of equinoxes, but nobody seems to mind. The reason is that phenomena like ingress into a zodiacal sign are not visible to the eye. Since eclipses can be timed now with great accuracy, their computation is  not done traditionally but    on the basis of modern algorithms. 

Much of the contemporary interest still centres on the astrological universe.( Use of high technology as represented by the computers  along with the  insecurities  introduced by globalization  seems to have  lent new legitimacy  to astrology.)  The  interest in  the  progress since, for some reason,   extends only to black holes and the origin of the universe. This is probably so because here the difference between the layperson and the expert gets blurred. All  astronomical developments in between  commonly leave the laypersons rather unenthused.

Science modifies sacred texts

We have  already seen how astronomical tradition was influenced by the Vedic. But  the traffic was two-way. Early  Vedic mythology attributed the eclipses to a demon Rahu, who is explicitly named in  Atharvaveda. Chhandogya Upanishad declares that a  soul which has  acquired pure knowledge is liberated  from the body   like the moon becoming free from Rahu. ( Kane V.1: 569) The correct mathematical theory of eclipses, which probably made its appearance in India about 100 BCE or so , points out that for an eclipse to occur the moon should be at one of its nodes, that is, at one of the two points where the lunar orbit intersects the ecliptic. The term Rahu was borrowed from the Vedic texts and applied to the lunar node, especially the ascending node (when the moon crossed the ecliptic moving northwards). The other node was termed Ketu. Maitrayani Upanishad mentions both Rahu and Ketu ( Kane  V.1:569). Incidentally this also tells us that the  Vedantic part of the  corpus was still open say about zero CE. 

At a more popular level  an elaborate  mythology was created to cut the old single demon Rahu  into two . The head retained the old name  while the  torso  was called Ketu. Subsequently the concept of Rahu and Ketu travelled outside India also. Burma knew of Rahu as Yahu ( Kochhar 1990) Interestingly,  in China while Rahu stood for the ascending node, Ketu denoted the lunar apogee, an identification not known in India.

 It is noteworthy that no religious, spiritual or revealed text or folklore has ever contradicted what the people at the time accepted as scientific knowledge. There is a basic difference between scientific tradition and the  other societal traditions. Science is inherently progressive. It continually updates itself.  There is no concept of frozenness associated with it.  On the other hand  the textual content of sacred tradition or folklore remains open for a while during which it takes note of contemporaneous scientific developments. But then it  becomes static and at times even may see later scientific developments antagonistically. (Hindu society has tended to accept modern scientific discoveries through the side door, by pretending that they were known to the ancient scriptures!) 

Appendix 1: Creation chronology 

The Rgveda uses yuga in the sense of a time-span, an age, or a generation. Vedanga Jyotisha refers to a five-year yuga. Atharvaveda  mentions in order 100 years, 1000 years, ayuta (10,000 years) and then two, three or four yugas. This suggests that a yuga here means an ayuta. The yuga-system as now commonly understood is set forth in the relatively late Vedic text Manusmrti (1.68-1.86), and expanded in the various Puranas.

In the Vedic times, a year comprised 12 months and 360 days. A human year was set equal to a day of the gods, so that a divine year (Dyr) would consist of 360 human years (yr).The divine year in turn was used to construct an elaborate chronology.

A mahayuga or chaturyuga (great age or four-age) was postulated as made up of four sub-ages or yugas: kaliyuga, dvaparayuga, tretayuga and krtayuga, with lengths in the ratio 1:2:3:4. The names are significant. The two middle ones obviously refer to the second and the third. The names of the two end yugas are taken from the game of dice, kali referring to one, and krta to four. The numbering is thus backwards, kaliyuga being the shortest and the latest.

It will be convenient to use mathematical notation to properly understand the formulation of the yuga system. A kaliyuga is said to contain 1200 Dyr. Let us denote the duration of a kaliyuga by the symbol k and of a mahayuga by m. dvapara, treta and krta are then 2k,3k and 4k respectively, so that

m=k+2k+3k+4k=10k.

For later reference, let us denote a krtayuga (=4k) by s. Then

6m=60k=15s.

We now construct a still bigger time-span called kalpa, comprising 1000 mahayugas. To complicate matters, let us introduce structure into a kalpa as follows:

1 kalpa 

      =1000m

      = 994m+6m     

       =14 x 71m+15s   

        =14x71m+14s+s  

        =s+14(71m+s).

Let us call 71m a Manvantara (Manu’s interval) so called because this span is presided over by a ruler designated Manu. (There are thus 14 Manus.) We can now describe a kalpa in words. A kalpa begins with a dawn equal to a krtayuga. This dawn is followed in succession by 14 Manvantaras, at the end of each of which there occurs a deluge (pralaya) lasting a krtayuga. This complex scheme has perplexed many modern-day commentators. Thus, Ebenezer Burgess in his famous 1860 annotated translation of the Surya Siddhanta declared: “Why the factors fourteen and seventy – one were thus used in making up the Aeon [kalpa] is not obvious” (Ebnezer 1860:11). I think this scheme was constructed working backwards from the neat round figure of 1000.

To sum up so far, a kalpa comprises 1000 mahayugas, with one mahayuga equaling in length ten kaliyugas. It now remains to give recognizable values to these numbers. A kaliyuga was set equal to 1200 divine years. Recalling that a divine year consists of 360 (human) years, we can express the yugas in human years:

      Kaliyuga   =4, 32,000 yr

      Mahayuga=4.32×10⁶ yr

      Kalpa       =4.32×10⁹  yr.

Kalpa becomes the basis for constructing a chronology for Brahma, the supreme creator. A kalpa is set equal to Brahma’s day or night. 360 kalpa pairs define Brahma’s year, 100 years making his life-span. Currently, we are in the midst of Brahma’s life. He has completed 50 years of his life. In the current kalpa seven out of the fourteen Manvantara are over, and so on.

References

Burgess, Ebenezer (1860) The Surya Siddhanta (reprint; Delhi: Motilal Banarsidass, 2005)

Kane, P.V. (1977) History of Dharmasastra, Vol. V. ( Poona : Bhandarkar Oriental Research Institute)

Kochhar, R.K. (1990) “Rahu in Burmese tradition (Correspondence) ”. Quart. J. R. Astr. Soc., 31,257

Kochhar Rajesh (1993) “ Historical perspective”. In: Astronomy in India : Past, Present and Future ( eds.: Rajesh Kochhar and Jayant Narlikar) ( Pune : IUCAA)

Kochhar, Rajesh (2000) The Vedic People: Their History and Geography (Hyderabad:Orient Longman)

Kochhar, Rajesh (2008) “Cultivation of science in the 19^th century Bengal”. Indian Journal of Physics, 82(8), 1003-1082. (Akshoy Datta Memorial Lecture at Indian Association for the Cultivation of  Science, Kolkata.)

     Kochhar, Rajesh (2008) “Seductive orientalism: English education and modern science in colonial India”. Social Scientist, 36:45-63. (S.C.  Mishra Lecture at 68^th Indian History Congress,   Delhi.)

Mani, Vettam (1975) Puranic Encyclopaedia (Delhi: Motilal Banarasidass)

Neugebauer, Otto (1983) Astronomy and History: Selected Essays (New York: Springer)//