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

322 BRAHMAGUPTA A GREAT CRITIC Maṅgalavāra (Tuesday), (Budhavāra) (Wednesday), Guruvāra (Thursday) Śukravāra (Friday) and Śanivāra (Saturday). Thus Āryabhaṭa gives the same order of days as other authorities and there is no reason why he should be criticised. Certainly what is Sunday for Laṅkā, may not be Sunday at the same time for Siddhapura; and Āryabhaṭa should have emphasised that the day (Monday, Tuesday etc.) is not cons- tant for all the places.¹ 10. Brahmagupta expresses surprise why Āryabhaṭa, in two of his treatises propounds two different systems of reckoning one from the Sunrise in Laṅkā and the other from the Midnight in Laṅkā.² This causes a difference of one-fourth of the daily- motion in the two reckonings of the motion of planets.³ 11. Brahmagupta criticises Āryabhaṭa on the point of dia- meter of the Earth. In the Gītikāpāda, 5 and 6, Āryabhaṭa states that one yojana = 8,000 × puruṣa, and 1 puruṣa = 4 hasta, thus 1 yojana = 32,000 puruṣas, and the diameter of the Earth is 1050 yojanas. Brahmagupta further says that an error in the diameter of the Earth would cause an error in deśāntara or longitude and thus also in the true tithi and consequently in the calculation of eclipses also.⁴ 12. Āryabhaṭa has rightly stated that the Earth is in motion and the Bhagaṇas are stationary. Brahmagupta's objec- tion is that if the Earth is in motion, birds would not be able to return to their nests, and if the Earth's motion is upside-down,

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1. सूर्याद्यश्चतुर्थी दिनवारा यदुवाच तदसदार्यभटः । लङ्कोदयो यतोऽर्कं स्यास्तमयं प्राह सिद्धपुरे ॥ — BrSpSi. XI. 12
2. अधिकैः शतैश्चतुर्भिर्वर्षसहस्रै रचतुर्दशभिरेकः । युगपाद्दिनवारान्तर मौदयिकार्ध रात्रिकयोः ॥ — BrSpSi. XI. 13.
3. औदयिकाद्दिनमुक्त गत्यंशो नार्ध रात्रिको भवत्यूनः । कतरं स्फुटं न निश्चितमनयोः स्फुटमेकमपि नातः ॥ — BrSpSi. XI. 14
4. षोडशगणितोजनरिधिं प्रतिभूव्यासं पुलावदतः । आत्मानं र या.पितमनिश्चयस्तनि कृतकन्द्यात् ।। भूव्यासस्याज्ञानाद् व्यर्थ देशान्तरं तदज्ञानात् । स्फुटतिथ्यज्ञानात् तिथिनाशाद् ग्रहणयोर्नाशः ॥ — BrSpSi. XI. 15-16