Rajesh Kochhar

ASTRONOMY
THE SCIENCE OF DIWALI

Divine Stargazing

For the devout Hindu, the period from Navratri to Diwali is the most important. Does it have an astronomical significance? Rajesh Kochhar, astrophysicist and director of the Delhi-based National Institute of Science, Technology and Development Studies, argues so. The two Navratris in a year, Kochhar said in a recent lecture, correspond with the equinoxes.

The Siddhantic calendar, the basis of all Hindu rituals, uses a lunar month. So does the Islamic Hejira calendar. A Hejira year, however, ends after 12 lunations-the time between two successive new moons, roughly corresponding to four weeks. The Siddhantic year occasionally-seven times out of 19, to be precise-allows for 13 months, “so that the year remains as close as possible to the 365-day solar year”. Each Siddhantic month has 30 tithis, “days” of unequal duration.

The last full moon of a Siddhantic year is celebrated as Holi. The new year is ushered in with a nine-tithi Navratri I, ending in Ram Navami. Six months later comes Navratri II, heralding the month of Ashvina, which contains the vernal equinox. The eighth and ninth tithis of Navratri II are dedicated to Durga. The next tithi is Dussehra. The new moon following Dussehra is Diwali. The next full moon is Nanak Jayanti.

The Siddhantic cycle repeats itself after 19 years. So the calendar for 2001 will recur in 2020. “The Siddhantic calendar,” Kochhar concludes, “is a fascinating living document because its elements have been calculated orally for 1,500 years. It deserves a close look from a civilisational and intellectual point of view, not merely for the sake of festivals and gazetted holidays.” Amen.