Indian Science and Technology in the Eighteenth Century: Some Contemporary European Accounts c9.54

c9.54

33. The equation of the sun’s centre is an element in the Indian astronomy, which has a more unequivocal appearance of belonging to an earlier period than the Calyougham. The maximum of that equation is fixed, in these tables, at 2°, 10′, 32″. It is at present, according to M. De La Caille, 1°, 55½′, that is, 15′ less than with the Brahmins. Now, M. De La Grange has shown, that the sun’s equation, together with the eccentricity of the earth’s orbit, on which it depends, is subject to alternate diminution and increase, and accordingly has been diminishing for many ages. In the year 3102 before our era, that equation was 2°, 6′, 28½″; less, only by 4′, than in the tables of the Brahmins. But if we suppose the Indian astronomy to be founded on observations that preceded the Calyougham, the determination of this equation will be found to be still more exact. Twelve hundred years before the commencement of that period, or about 4300 years before our era, it appears, by computing from M. De La Grange’s formula, that the equation of the sun’s centre was actually 2°, 8′, 16″; so that if the Indian astronomy be as old as that period, its error with respect to this equation is but of 2′.53