The Suryasiddhanta: The Astronomical Principles of the Text

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The Asiatic Society feels proud in publishing the Surya-siddhanta, the much acclaimed astronomical text written in Sanskrit in between 10th and 11th Century A.D. Professor A.K. Chakravarty has done a Herculean task by arranging the contents and recasting the chapters of the text. He has moved heaven and earth to get in touch with various commentaries written on this valuable text and to develop his research-work after consulting the observations made on the Surya-siddhanta by Burgess, Swami Vijanananda, Sudhakar Dvivedi, K. S. Sukla, as well as the relevant papers published in different journals. Sanskrit literature on Technical Science was very rich and it started from 5th-6th Century A.D. But because of its archaic nature and form, the texts in this branch can only be explained or interpreted by scholars having scientific acumen aid at the same time possessing enough proficiency in Sanskrit language. Fortunately Professor Chakravarty is endowed with both the faculties for which his strenuous effort has reached a complete success. The complete text has been included in the Journal of the Asiatic Society, Vol. XLII, Nos. 3-4, 2000, now it is getting the shape of a book. I believe his book will add a special glory to the Department of Publication of the Asiatic Society and scholars will certainly be benefited by this esteemed work.

The Surya-siddhdnta, also called the modern Surya-siddhdnta, has the largest number of commentators among all the astronomical texts written in India, it has been translated into almost all the regional languages of India. In all Sanskrit Colleges where Jyotisa is included in the curriculum the Surya-siddhdnta is followed as a class room text book, and so, plenty of explanatory notes on it, either in manuscript or in printed form are also available now. And so we perhaps owe an explanation as to why we are writing another edition of it.

Despite the inherent beauty of the text written in the 10th or 11th century, the chapter-wise distribution of the subject is neither uniform nor systematic. Observes Rev. Burgess: "The treatise, however, is now here distinguished for its orderly and consistent arrangement". In most cases the chapters are not self-contained, precise definitions are often wanting, and conjectural metaphysics has often been invoked. The chapter wise distribution of topics in this text differs so sharply from that as found in present day class room text book on astronomy that a reader even after completing a college course on spherical astronomy can hardly follow the entire text.

We, instead of giving verse—for-verse English translation of the text with annotations, have only redistributed the entire content of the text following the conventional chapter wise distribution of the subject as followed in standard text books on astronomy, but in all cases we have given reference to the original verse of the text in braces e. g., (Ill, 16-17) will mean verses 16 to 17 in chapter III of the text. We make a special mention of it so that the reader may not confuse with the reference numbers we have used in our equations.

Proofs of many of the statements become immensely simplified by application of formulae of spherical trigonometry. Some modern commentators have also used spherical trigonometry in their annotations. But the mathematical formulations used by conservative commentators are limited to application of Pythagoras' theorem and similarity of triangles. We have, willingly, avoided spherical trigonometry and have used the technique of the commentators. The text has given a table of sines, but this table has been used in the text only for reducing half chords to arcs or the other way, and formulations of spherical trigonometry have nowhere been used in the text. To maintain this tradition of the text we have not used spherical trigonometry.

Some verses are sufficiently clear in meaning and do not require any elaboration, and, in such cases, we have only reproduced the concerned verses without any explanatory notes.

Many of the verses of the text are incomplete or erroneous, only the commentator has rectified or elaborated them. In such cases we have followed the commentator, but have also mentioned the original statement of the text.

We have given in braces the Sanskrit equivalent words of the technical terms, but such equivalent words are not uniform. Vrtta has been used to denote both great and small circles, often the term Mandala has also been used in the same sense. Sanku may mean a standard gnomon of length 12 angulas or the vertical height of the sun or a planet from observer‘s horizontal plane and so on. We have taken care so that the reader may not be confused in such cases.

The diagrams in the commentaries are, in most cases, projections of one or another spherical triangle in the horizontal or meridian plane, and, in some cases, the arcs of the triangle to be projected are not great circle arcs. A present day astronomy student is more accustomed to drawing diagrams of the celestial sphere than projecting a triangle in one or another plane. To avoid such diagrams of projections we have drawn diagrams of the celestial sphere with which the reader is already familiar, and this is an important point where we have deviated from the commentary.

The popularity of the Surya-Siddhanta becomes apparent from the following considerations. Till now, 26 commentaries of this text have been found in different libraries and private collections, and another 8commentaries by anonymous authors are also extant. Of all these, only two commentaries are available in printed form, one by Ranganatha (AD.1603) and another by Paramesvara (A.D. 1432). An interested reader will find a detailed account of all these commentaries and the libraries where they are preserved in K.S. Sukla’s Surya-siddhanta published by Department of Mathematics and Astronomy, Lucknow University (1957).

Apart from these two printed commentaries, another three manuscripts composed by Mallikarjun Suri (A.D. 1178), Yallaya (A.D. 1472), and Ramakrsna (1472) are often referred to in astronomical works.

Whereas the contents of all these manuscripts are, more or less, the same, still readings differ widely in all these works. For example's sake, we mention here that we have the readings : (ch I, 43) trikhanka bhargavasya (M), trikhankasca bhrgostatha (R), trikhankani bhrgostatha (Y),trikhankani bhrgostatha (Ra), trikhankasca gurostatha (P) with a note guroh daityaguroh. Such variations are of clerical nature and do not have any bearing on the context. An exhaustive account of such variations will be found in KS. Sukla's edition of the text.

We consulted the works of Burgess (Motilal Banarsidass reprint, Delhi,1989), Swami Vijnanananda (Calcutta; 1983, second edition), M.M. Sudhakar Dvivedi (Sampurnananda Sanskrit University, Baranasi, 1987),K.S. Sukla, and the several papers published in the Asiatick Researches. We, however, have followed the text of Ranganathas commentary as given in Dvivedi’s text, and the work of Burgess for English translation.

The text given in the appendix has been taken from Ranganatha’s commentary.

Our original plan was to devote equal space to the different chapters in our work, but while preparing the manuscript we could not maintain it. We, as a result, were pressed to include such topics in the same chapter in some cases which are, in fact, not mutually related. Still we have taken care, as far as possible, to see that the distribution of topics may not be unbalanced and at the same time distribution of space chapter wise may not be too uneven.

The definitions, formulations and astronomical parameters of this text are, in most cases, the same as their counterparts in the works of Aryabhata, Brahmagupta and Lalla, and in some cases they differ only slightly. But in some cases they differ so sharply that we made a special reference to them in the appendix.

So far as we are aware, no attempt was made earlier to present the contents of the text in such a form after recasting the chapters of the text. Only the reader can judge if the text has become simplified by this way of presentation.

I received some financial support from the Asiatic Society for this work, and without this support l perhaps could not have undertaken this work. I express my gratitude to the Asiatic Society for sanctioning me this financial support. I am also grateful to staff of the Library Photography section and Manuscript section of the Society for the cooperation I constantly received from them.

I thank the staff of M/s PAB computers for rendering so much satisfactory services to me in connection with the preparation of press copy.