152 EPICYCLIC THEORY OF ANCIENT INDIANS a mean inferior planet or the mean Sun. EA the direction of the V apogee of apsis and ES that of the sighra. The inequality of the apsis takes the mean geocentric planet from M to M₁, such that MM, is parallel to EA. Let EM, be joined cutting the con- centric at M₁ M₂ is taken as the centre of the sighra epicyle or the real circular orbit in which the appa- rent planet moves. 1 E A Fig. 18 With M, as the centre and the radius of the inferior pla- nents' ghra epicycle as radius, describe the circle NVU which is here the fighra epicycle or the real circular orbit. In it draw the radius M₂V parallel to ES; then VP is the geocentric position of the inferior planet. Here the first displacement MM₁ is due to the inequality of apsis and is for finding the position of M, the centre of the real circular orbit. The idea was that the apparent planet moved in a circular orbit of which the centre was very near the mean position of the Sun, the first operation in this construction was calculated to determine the centre of this so-called circular orbit of an inferior planet. The saghra of an inferior planet moves round the Earth at the same mean rate in which the inferior planet moves round the Sun; hence the line ES in this figure is always parallel to the line joining the Sun to the mean heliocentric inferior planet, and in our construction, it is parallel to M.V. This in brief is an outline of the Indian idea of planetary motion as taught by Aryabhata I, Brahmagupta and Bhaskara II. Reference P.C. Sengupta: The Khandakhadyaka. 1934.
