Chapter on Mean Motions

It is not explicitly stated what is meant by "clearly explained," yet because the values for planetary revolutions and other measurements are identical, Brahmagupta accepted the Brahma-siddhanta found within the Vishnudharmottara Purana as his authoritative source original: "Agama," meaning sacred tradition or authoritative source. In the chapter titled "Examination of Tantras," while describing the views of the compilers of the Samhitas—such as the idea that "a Yuga consists of five years"—it becomes clear that in Brahmagupta’s view, the Jyotisha Vedanga The ancient astronomical auxiliary to the Vedas is not the same as the Brahma tradition. Expert mathematicians should understand that this differs from the opinion of Varahamihira. This is also proven by the statement of Kamalakar in the Siddhanta-tattva-viveka: "Alas, even the Vishnudharmottara was not properly understood." It is not found anywhere in the Brahmasphuta-siddhanta exactly how the original Brahma-siddhanta became corrupted or loosened over the vast passage of time, nor how Brahmagupta specifically rectified those errors. Whether his claims are factual or otherwise is for discerning mathematicians to judge. || 2 ||

Now, the reason for beginning this work is stated.

Hindi Commentary: The planetary mathematics narrated by Brahma (the Brahma-siddhanta) became "worn out" or corrupted original: "khilatva," referring to a text becoming obsolete or full of errors over time due to the long passage of time. Therefore, I, Brahmagupta, the son of Jishnu, am stating it clearly. At present, three versions of the Brahma-siddhanta are available: first, the one within the Shakalya Samhita; second, the prose version within the Vishnudharmottara Purana; and third, the version describing a five-year Yuga found in Varahamihira’s Pancha-siddhantika.

Among these three, Brahmagupta does not explicitly say which one he is clarifying. However, because the planetary revolution counts match, he accepts the Brahma-siddhanta from the Vishnudharmottara Purana as his authoritative tradition. It is clear that Brahmagupta does not consider the Jyotisha Vedanga to be the true Brahma tradition, as he critiques the "five-year Yuga" mentioned by the Samhita authors. This contradicts the view of the teacher Varahamihira; mathematicians should reflect on this. This is also evident from Kamalakar’s remark in the Siddhanta-tattva-viveka: "Alas, even the Vishnudharmottara was not properly understood." How the Brahma-siddhanta lost its precision over time and how Brahmagupta corrected it is not detailed in this text. Discerning astronomers should judge if these statements are correct. || 2 ||

Now he describes the motion of the celestial sphere, including the planets, which is the foundation of the science of light (astronomy).

The celestial sphere, bound to the Pole Star, was created by Brahma in the beginning, moving eastward, along with the planets situated at the junction of the constellations Revati and Ashvini. || 3 ||

Sanskrit Commentary: "At the junction of Revati and Ashvini" original: "Paushna" refers to the star Revati; "Ashvini" is the first nakshatra means the planets (the Sun and others) were placed at the meeting point of these two constellations. "The celestial sphere bound to the Pole Star" refers to the circle of lights—the luminous stars and other celestial bodies (the Zodiac)—which is fixed to the axis or rod passing through the two poles.