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

EARTH ROTATION 9
opinion appears nevertheless satisfactory, since planets cannot
have two motions at once : and the objection, that lofty things
would fall, is contradicted; for every way the under part of the
Earth is also the upper; since wherever the spectator stands on
the Earth's surface, even that spot is the uppermost spot.¹
Earth rotation by a current of aerial fluid
It is very interesting to see the theory once advocated by
Herakleides of Pontus transplanted on Indian soil, especially when
we remember that Seleukus, the Babylonian, had adopted that
theory. From Babylon the theory might easily find its way to
India, though it is of course equally possible that Āryabhaṭa,
quite independently of his Greek precursors, hit on the same
idea. He appears to have accounted for the Earth's rotation by
a wind or current of aerial fluid, the extent of which, according
to the orbit assigned to it by him, corresponds to an elevation
of little more than a hundred miles (114) from the surface of the
Earth, or fifteen yojana's while he put the diameter of the Earth
equal to 1050 yojanas (of 7.6. miles each²). This was in accordance
with the general opinion of the Indians, that the planets are
carried along their orbits by mighty winds with the same velo-
city and parallel to the ecliptic (while one great vortex carries all
stars round the Earth in twenty-four hours, but that the planets
are deflected from these courses by certain invisible powers
having hands and reins, with which they draw the planets out
of their uniform progress. The power at the apogee, for. instance
constantly attracts the planet towards itself, alternately with
the right and left hand (like Lachesis in Plato's Republic), while
the deity at the node diverts the planet from the ecliptic first to
one side and then to the other. And lastly the deity at the con-
junction causes the planet to move with variable velocity and to
become occasionally stationary and even retrograde. This is
gravely set forth in the Sūrya-śiddhānta, and even Bhāskara gives
the theory in his notes, though he omits it from his text.
Similarly Brahmagupta, although he gives the theory of eclipses,
affirms the existence of an eighth planet, Rāhu, which is the
immediate cause of eclipses; and he blames Varāhamihira,

1. Asiat. Res, XII, p. 227; Colebrooke's Essays, II, p. 392.
2. Colebrooke, Notes and Illustrations to the Algebra of Brahmagupta, p.
   xxxviii. Essays, II. p. 467.