Genesis' cosmogony

This essay discusses what the Torah and it's mainstream medieval jewish interpreters have to say about creation and the age of the universe 

There is a fundamental disagreement about how to render the very first word in the Torah, and by extension, the first few pesukim, with wide ranging implication. 

Rashi and his grandson Rashbam interpret it as "At the beg. of God's creating heaven and earth (end of verse 1) and the earth was desolate and empty . . ". 

Ramban and Radak read it as the more familiar "In the beginning, God created heaven and earth". 

The ta'amim concur with the latter opinion (there is a disjunctive tipcha under "bereishis"). 

Rashi famously kicks off his commentary by citing a midrash to the effect that the Torah should rightfully have started with the first mitzvah and skipped all the historical drama, see there. Ramban rejects its plain reading as for Ramban it is axiomatic that God created the world, as otherwise (in an eternal universe model) Judaism falls, see there his creative reading to have it conform with his opinion.

Ramban's reading of the first pasuk also furnishes him with an explicit pasuk affirming the belief of creation ex nihilo. 

Ramban also rejects any non literal reading of the first six days of creation, giving us a world less than six thousand years old. 

Otoh, Rashi & Rashbam's reading leave the door open to a potentially long existing (Rashbams language is הן זמן מרובה הן זמן מועט) and unfinished shamayim and aretz which are now the subject of Gods finishing touches.

Aristotle's conception of an eternal and static universe held sway for about two and a half thousand years (with Rambam famously saying that were it to have been sufficiently proven [or demonstrated, to use the lingo] he wouldn't have any more issue reading it into the Torah than any of the many anthropomorphisms that he reinterpreted in light of his belief in God's incorporeality), right up until the early decades of the 20th century when Einstein's equations and Hubble's telescope showed that the universe was expanding and in perpetual motion—a death knell for Aristotle. 

It took the scientific community (including Einstein himself) time to warm to the idea, especially as it points toward a starting point which in turn indicates a Starter which seems uncomfortably reminiscent of—gasp!—a creator God. 

Ramban writes that והנה בבריאה הזאת, שהיא כנקודה קטנה דקה ואין בה ממש, נבראו כל הנבראים בשמים ובארץ. 

If we combine Rashbam's murky timeframe with Ramban's conception of creation's mechanics, we emerge with something potentially approximating the age of the universe according to current scientific belief as well as its prevailing cosmogony—the big bang theory (albeit with a Big Banger).

However, what is truly important, even if there is debate on the details, is that HaShem intentionally created and shaped the world as we know it and that there is meaning and purpose to our lives.