Atri's Solar Eclipse

In the 5th Mandala of Rig Veda, the 40th sukta and 5th Rik, Rishi Atri describes a total solar eclipse.

Rig Veda- HYMN XL. 5.
Indra. Surya. Atri.

O Surya, when the Asura's descendant Svarbhanu, pierced thee through and through with darkness, All creatures looked like one who is bewildered, who knoweth not the place where he is standing.

Vedic astrology refers to moon’s ascending node or descending node at time of potential solar eclipse as Rahu or Swarbhanu, a demon. The passage certainly describes a total solar eclipse, magically imposed by Rahu, and people and animals being scared of the solar eclipse event .The same material is expanded in Kaushitiki or Sankhyayana Brahmana. 24.4.

In this segment reference is made to eclipse occurring three days before autumnal equinox. In Vedic times, equinoxes and solstices were well understood. Devayana (period of sun motion of gods) referred to time from spring equinox to autumnal equinox when sun stayed north of equator. Pitrayana (period of ancestral sun motion) referred to time from autumnal equinox to spring equinox when sun stayed south of equator. Gradually at later periods, but still historically at an old time, the Uttaraayana (Northerly motion of sun) from winter solstice to summer solstice and Dakshinayana (Southerly motion of sun) from summer solstice to winter solstice replaced the Devayana-Pitrayana use. Atri’s reference to Vishuvantam or autumnal equinox in context of Atri’s solar eclipse is significant and explicit. Though Vishuvat stands for both equinoxes, the use in this context is taken to be autumnal because of beginning of Pitrayana.

Thus Atri’s RV 40-5 and Sankhyayana 24-4 provide us with details of a total solar eclipse occurring three days before autumnal equinox. Is this data unique enough to retro date the solar eclipse event and Atri’s time?

When European Indologists could translate and understand Rig Veda in late 1800’s Atri’s Solar eclipse and its astronomical implications caused a lot of excitement. Efforts were made to date the eclipse and hence Rig Veda. However, in those days without computers and precise mathematical models of sun-earth-moon motions currently available (in this present satellite era), retro dating of eclipses was difficult and results were ambiguous and unsuccessful. Dominance of Saros cycle approach resulted in too numerous solutions. B.G.Tilak, in his book Orion, describes the various efforts during his time.

Retro eclipse dating of eclipse events is a new approach to date historical events based on declared eclipses and their circumstances. Modern computer modeling of finely tuned heavenly body motion allow very precise calculation of the terrestrial eclipse times in ‘Universal Time’ frame. The only issue in retro dating is that there is a difference between ‘Universal Time’ and ‘Terrestrial Time’. Because of continuously changing difference, retro dating has some uncertainty. The earth’s rotation is inertial. Earths rotational momentum is always conserved, but the rotational speed varies with inertial distribution as mass on earth, which can slightly redistribute. This is similar to an ice skater changing spinning rate by inertia adjustment through hands. As the magma inside the earths core, ice ages, earthquake (like recent Indonesian Tsunami of 2005), all make miniscule changes earth’s inertia. This results in changes to earth’s rotational speed. Rotational speed change results in terrestrial time shifts relative to universal time. The time error is not large but can integrate to big numbers over thousands of years. This is called the delta T problem.