Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c15.s2.1

v2.c15.s2.1

We have already seen the various phases through which our growing science of astronomy has passed. If works compiled before Varāha mihira and those in the intervening period between Brahmagupta and Rājamṛgāṅka would become accessible, we would know more of the history of the science. Research work in the Saṃhitā Branch came to a standstill very soon after Varāha. The mathematical branch was in a flourishing condition till about Śaka 1000. Bhāskarācārya’s treatises threw into the shade most of the previous works and from that time onwards the theory propounded in Bhāskara’s works came to be regarded as the alpha and omega of the knowledge of astronomy. As the divorce between planetary calculations and the realities of the heavens became more palpable in course of time, there appeared on the scene some annonymous bīja*-finder of the Sūrya Siddhānta, as also Keśava Daivajña and Gaṇeśa Daivajña, and they rectified the elements of the planets. They could not, however, revitalize the science and ensure its future growth. The corrections (bīja-saṃskāras) proved to be mere makeshifts of the moment in the absence of the tradition of recording observations, and these corrections were in certain respects not quite accurate. Another great drawback of such corrections was that they led to the general belief that the difference between the results of calculation and those of observation was due to a cumulative error traceable right back to the beginning of the Kaliyuga, and hence the corrections were so devised that the error which had really accumulated in a few years was spread over a very long period. Consequently the corrections could not remain valid for a long time, and in certain cases they proved useless from the very beginning. A glaring instance of this is that the year-length once handed down in the remote past was never corrected later, with the result that at present the correction of the year-length has become the toughest problem affecting the question of calendar reform. Even though Brahmagupta noticed that the equinox receded a day, he distributed the difference over a period of 3700 years according to the traditional belief, that all variations originated at the beginning of Kaliyuga, though in reality the difference was the result of the error accumulating since Āryabhaṭa's time, that is, a period of about 150 years. Otherwise, Brahmagupta himself could have introduced the measure of the tropical year; and once he had introduced it, calendar reform would not have been an uphill task as at present. Even the observations of Keśava and Gaṇeśa proved to be of little use. Had there been a record of past observations, it would have been of much use to them for comparing results. In short, although corrections were applied from time to time, they could rectify the planetary elements only for the time being.