Siddhanta Shiromani (Crown of Treatises)

Through these direct and retrograde motions, the status of the planets' positions is understood. When the distance from the Fast Apex śīghra The point of conjunction which governs the planet's faster motion is subtracted, the position of the planet is determined. Because of the relative smallness or greatness of the orbits and their proximity or distance, the speeds vary.

Due to the size of the fast epicycle, at the seventh sign, Venus and Mars original: "भृगुभूपुत्रौ" — bhṛgu-bhūputrau, and at the ninth sign, Jupiter, Mercury, and Saturn original: "जीवशशिजौ... शनैश्चर" — jīva-śaśijau... śanaiścara experience a change in motion. Their speed increases or decreases, leading to Retrograde Motion vakra Apparent backward motion of a planet or Quasi-retrograde Motion anuvakra.

When the Equation of the Fast Apex śīghra-phala is subtracted from or added to the mean motion, we determine the true daily velocity. If the Slow Equation manda-phala is negative, the motion is slower; if the Fast Equation is strongly positive, the motion is swifter. We shall explain this in great detail in the chapter on the Mean Motion of Planets madhyamādhikāra.

The Beginning of Time

Now, the author describes the commencement of the science of Time:

"In the city of Lanka, at the rising of the Sun, on the Sun’s own day [Sunday], there occurred the simultaneous beginning of the day, the month, the year, and the Eons yuga, starting from the first day of the bright half of the month of Madhu The month of Caitra, marking the beginning of Spring.."

This means that starting from sunrise in the city of Lanka In ancient Indian geography, Lanka refers to a theoretical point on the equator where the prime meridian of Ujjain intersects it, serving as the "Greenwich" of the Sanskrit astronomical tradition., on a Sunday, the various measures of time began. This includes solar, lunar, and civil days, as well as months, years, and the great cycles known as Yugas, Manvantaras, and the Kalpa A 'Kalpa' is a vast cosmic period, often called a 'Day of Brahma,' totaling 4.32 billion years..

All of these began simultaneously. This implies that at the very start of the Kalpa, all the planets were positioned exactly at the beginning of the zodiac—at the first point of Aries meṣādi.