# Senthil Kumaran

## Book Review: Indian Astronomy - A Primer

Indian Astronomy - A Primer by Dr. S. Balachandra Rao
My rating: 5 of 5 stars

I read this book after I had completed reading the book The Greatest Inventions of the Past 2,000 Years. In that, I noted down the contributions of The Indo-Arabic Number System as one of the significant inventions in the past 2000 years.

The important thing to note was, the positional value number system along with 0 was invented a 1000 years before the birth of Christ and it was systematized by Aryabhatta in the year 499 CE.

This greatly increased my curiosity for Indian mathematics. The book was a boon in that regard. It dwells with the Indian Astronomy, mathematics with a verifiable accuracy. We are given a survey of Astronomy in , Vedanga Jyotisa , Siddhantha (established truth), and giving the information about Aryabhatta I, Bhaskaracharya. It goes into details about Zodiacs and constellations (as calculated by the astronomers), Yuga System and Eras.

I came to know that Kali Yuga commenced on 17/18 February 3102 BCE, at the demise of Krishna.
So, as of this writing of the review, we have been living in **5119 years** since the start of Kali Yuga (an epoch).

The book also introduced me to the concept of Luni-solar months, were lunar months are pegged upon to solar months. The metric value is called Ahargana,. In Sanskrit 'ahoratra' means one full day and 'gana' means count. Hence, the Ahargana on any given day stands for the number of lunar days that have elapsed starting from an epoch.

This is the counting system used in Indian calendars. After giving details about this, book then talks about Co-ordinate systems, Rasi and Naksatra systems, Panchanga (Panchaga means 5 parts which are Tithi, Naksatra, Vara, Yoga and Karana) and gives the reference for the calculation mean positions of Sun, Moon and Planets.

Given the words like "Panchanga", "Tithi" etc, one would expect this book to be written by some astrologer or might have some preachiness to it. This is where, I think, the book shines. No, it has none of the preachiness, it has none of the emotional or venerable expressions towards those concepts. Instead, those are presented as Indian mathematics, by done mathematicians in India when as they pursued their understanding of the universe and recorded them.

The book is written by Dr. S. Balachandra Rao is was a professor of Mathematics, who has published around 20 books in subjects ranging from Numerical methods, differential equations, calculus, Indian Astronomy, and mathematics.