Page:Aryabhatiya of Aryabhata, English translation.djvu/82

52 The word ucca refers both to mandocca ("apsis") and sighrocca ("conjunction").

Parameśvara explains that the number of revolutions of the epicycle of the apsis of the Moon is equal to the difference between the number of revolutions of the Moon and the revolutions of its apsis; that since the apsides of the six others are stationary, the number of revolutions of the epicycles of their apsides is equal to the number of revolutions of the planets; and that the number of revolutions of the epicycles of the conjunctions of Mercury, Venus, Mars, Jupiter, and Saturn is equal to the difference between the revolutions of the planets and the revolutions of their conjunctions.

As pointed out in the note to I, 7, the apsides were not regarded by Āryabhața as being stationary in the absolute sense. They were regarded by him as stationary for purposes of calculation at the time when his treatise was composed since their movements were very slow.

5. The revolutions of the Sun are solar years. The conjunctions of the Sun and Moon are lunar months. The conjunctions of the Sun and the Earth are [civil] days. The revolutions of the asterisms are sidereal days.

The word yoga applied to the Sun and the Earth (instead of bhagaņa or āvarta) seems clearly to indicate that Āryabhața believed in a rotation of the Earth (see IV, 48). Parameśvara's explanation, ravibhūyogaśahdena raver bhūparibhramaņam abhihitam, seems to be impossible.

6. Subtract the solar months in a yuga from the lunar months in a yuga. The result will be the number of intercalary months in