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

20 time. Hence the estimate of their mean motion by the Hindu Astronomers naturally went wrong. Noticing that the Mandoccha of the Moon has a progressive motion which the Hindu astronomers could measure correctly, they extended the analogy to the apogee of the Sun and the aphelia of the other planets whose motion also being very slow could not be measured during the life-time of a man. So here also the estimate of their mean motions of the Sun's apogee and the planetary aphelia went wrong. Bhaskarāchārya has given proofs as to how the sidereal revolutions could be got but as we shall see later in the Spaṣṭādhikāra, his proof occasionally suffers from what is called ‘इतरेतराश्रयदोष’ ie ‘begging the question’. We shall however construct our own proofs at that place deferring them for the present, for, the proofs require an elucidation which obtains in the Spaṣṭadhikāra alone. Verse 7. The number of diurnal revolutions of the stars in a Kalpa is 1582236450000. Comm. In fact this number is that of the diurnal rotations of the earth which is equal to the number of apparent diurnal rotations of the stars, if the earth is deemed as fixed. The only Hindu Astronomer who made bold to say that the earth is rotating and not the stars came under criticism by Brahmagupta and the latter Hindu astronomers. Aryabhata said अनुलोमगतिः नौस्थः पश्यत्यचलं विलोमगं यद्वत्, अचलानि भानि तद्वत् समपश्चिमगानि लङ्कायाम् ” ie Even as a man stationed on a moving boat perceives that the trees etc on the banks of the canal, river or lake to be moving in the opposite direction supposing himself statio- nary, so also men stationed on the surface of the earth (which is like a moving boat) perceive the actually statio- nary stars to be moving directly from east to west at Lanka ie the equator ”.