ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

CHAPTER VII
Epicyclic Theory
of Ancient Indians
We shall give here some details of the Indian concepts
regarding the motion of planets or wandering bodies among the
stars. The Vedāṅga Jyotiṣa (1400 B. C. or earlier) does not speak
of this, A comparison of the astronomical constants of the
Greek and the ancient Indian systems, points unmistakably to the
conclusion that the Indian constants as determined by Āryabhaṭa
I and his successors, are almost in all cases different from those
of Greeks. Indian astronomers were highly original in their con-
cepts and treatment. The originality of Āryabhaṭa I and other
astronomers would be seen from what we are discribing below.
Apparent Motions of the Sun and Moon
We have the following passages from Āryabhaṭa :
All planets move in eccentrics to their orbits at the mean
rates of angular motion, in the direction of the signs of the
zodiac from their apogees (or aphelia) and in the opposite
directions from their Śīghroccas.
The eccentric circles of planets are equal to their concentrics
and the centre of the eccentric is removed from the centre
of the Earth.
The distance between the centre of the Earth and the centre
of the eccentric is equal to the radius of the planet's epicycle;
on the circumference (whether of the epicycle or of the
eccentric) the planet undoubtedly moves with the mean
motion.
Here the central idea was that undou-
btedly planets moved unifomly in circles
round the Earth; if the motion appeared
to be variable, it was due to the fact that
the centres of such circle (i. e. the con-
centric circles) did not coincide with the
centre of the Earth.
Fig. 15