सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

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ning of the Kalpa, A modern astronomer, however, ques-
tions the assumption that the planets were all started at the
first point of the Zodiac, and even though they might all
have been in conjunction at that point in some remote
past, whether it was the initial point of the reported Kalpa.
Proceeding on the basis of the reported initial conjunction
of all the planets at the first point of the Zodiac, and calcu-
lating the number of days that have elapsed from the begin-
ning of the yuga, the mean positions of the Sun and the
Moon were computed. Noticing that these mean positions
did not exactly accord with the true observed positions, the
ancient astronomers tabulated the differences between those
mean and true positions. These differences were found to
be zero at two diametrically opposite points, and maximum
roughly at two points differing by a quadrant from them.
To account for these differences, the thought that occured
to their minds was that probably the Sun and Moon did
not move in a circle whose centre coincided with that of
the Earth but were moving in an eccentric circle i.e. a
circle whose centre is at some other point than the Earth's
centre. This surmise could be made because unequal
motion was accountable only on varying distance from the
Earth's centre and a celestial body appearing to move
fastest must be nearest whereas the same appearing to
move slowest must be farthest. Thus in the first place
seeing no reason for non-circular motions and also expec-
ting the celestial bodies to move only in circles, for, a
circular motion appealed to them as the most ideal motion,
the ancient astronomers later postulated an eccentric
circular motion with respect to the Sun and the Moon.
This postulation appeared to give good results as seen
below.
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