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

10 ASTRONOMY IN ANCIENT NATIONS
Āryabhaṭa and others for rejecting this orthodox explanation
of the phenomenon.¹
Indian astronomy some times appears to be a curious mix-
ture of old fantastic ideas and sober geometrical methods of
calculation. But it is wrong to presume that these geometric
calculations were derived from froeign contacts. Indians have
always been fond of geometry (from the earliest times of the Vedic
rituals), and they from the very beginning realised the impor-
tance of applying geometry to astronomy, Side by side we find
Greek contacts also. As remarked by Colebrooke, the absence
of the most characteristic parts of Ptolemy's system, the
equant and the details of the theories of the Moon and Mercury
seems to indicate that Greek planetary theory must have been
introduced in India between the times of Hipparchus and Ptole-
my; and with the exception of the epicycle from the circular
form, the Hindus did not modify the theory or perfect it in
any way. The precession of the equinoxes they held to consist
in a liberation within the limits of 27° (Āryabhaṭa says 24°) east
and west of its mean position, but they came much nearer to
the truth than Ptolemy did as regards the annual amount, as
they supposed the space travelled over in a century to be 1½°.
Contacts with Arabs
Notwithstanding some isolation of India from Europe
during the Middle Ages, her astronomy was destined to
exercise an indirect influence on the progress of astronomy.
Through the conquest of Persia in the seventh century,
the Arabs, like the Greeks a thousand years earlier, came
in contact with India, from whence physicians and astro-
logers found their way to the court of the Caliph already
before the reign of Harun al Rashid. We possess a detailed
account of the manner in which the Indian astronomy was
introduced at Baghdad, from the pen of the astronomer Ibn
al Adami (who died before 920), confirmed by the celebrated
memoir on India by Al Beruni, written in 1031². In the year
156 of the Hijra (A. D. 773), there appeared before the Caliph
Al Mansur a man who had come from India; he was skilled in

1. Asiat. Res. XII, pp. 233, 241; Essays, II, pp. 398, 407.
2. Hankel, Zur Geschichte der Mathematik im Alterthum and Mittelalter,
   Leipzig, 1874, p. 229; Cantor, Gesch. d. Math. I, p. 656.