I think you are on a slippery slope when you want to flirt with science, cosmology and religious text et all in one and the same thread. Let me try to elaborate: First let us take the case of science or big bang theory. Let us assume the theory is fully explained and accepted by all. Once this is achieved, the question will arise as to what caused the big bang and was it possible for such a cause to exist before, whether such big bangs did occur in the past and whether such past big bangs resulted in life or not. If it did, where are/were such life forms? If such big bangs did not result in life, why not? . Now let us take the varaha avatar episode. Who is that person who is narrating the episode? Where was he stationed when Maha Vishnu took out the earth from deep under waters (when there was no land mass)? Why was the narrator not consumed by the preceding maha pralaya? Was the narrator reporting the current developments or was he reporting the past incidences? Were the past incidences actually seen by him or were they narrated to him? If the original episode was narrated based on direct testimony of Maha Vishnu, the narrator should have been extremely fortunate to converse directly with Vishnu. What good deeds or karma did the narrator do to merit such such a face to face conversation with Vishnu.