A Concise History of Science in India c6.s3.4

c6.s3.4

Accurate study of heavenly bodies, in which the planets were gradually to be incorporated, involved the application of more sophisticated mathematics, adoption of a system of co-ordinates, and more reliable determination of their periods of revolution, the sizes of the earth, the relative sizes of the sun and the moon, and so on. Although interest in the eclipse phenomena had been very ancient and recorded at several places in the earliest *Saṃhitās* and the *Brāhmaṇas*, their calculations and predictions were beyond the scope of the kind of astronomy so far practised and taught. All this must have occupied the serious attention of the astronomers of this period, for by about A.D. 400 or even earlier we for the first time come across an altogether new class of astronomical works called *siddhāntas* dealing with matters and methods unknown in the works of any previous period. This new class of works is characterized, among others, by the replacement of the *nakṣatra* system by the 12 signs of the zodiac, the correct length of the year, the correct rules for calculating day-lengths and oblique ascensions, the determination of mean longitudes by the *ahargaṇa* method, the study of planetary motions by reference to a celestial sphere, the system of great and small circles and the geometric models of eccentric circles and epicycles, the ideas of parallax and its calculation, and the calculation of solar and lunar eclipses. The emphasis on computations also opened the way to new methods of analysis. Integral solutions of indeterminate equations, rudiments of plane and spherical trigonometry, besides common geometrical, arithmetical and algebraic practices, became integral parts of the new science. Increasing mathematization very soon necessitated the incorporation of a few chapters on mathematics into most treatises on astronomy, and the practice was carried to such an extent that astronomy and mathematics became inseparable for several centuries to come.