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Does the universe have a birthdate?

Via jaylake , Andrew Wheeler notes that yesterday was the 6012th anniversary of God's creation of the Earth, according to James Ussher's chronology.

These days, of course, the enlightened view is that God did not create the Earth 6012 years ago, but rather that the universe sprang into existence for unknown and possibly unknowable reasons approximately 13.7 billion years ago.

But thinking about Archbishop Ussher got me wondering: Whether or not it could ever actually be calculated, does the universe, under Big Bang theory, have a birthdate? Your typical Big Bang chronology lists various events -- e.g., the formation of the first atoms -- occurring X number of seconds or minutes after the Big Bang, which suggests that time as we understand it goes back to the beginning, which further suggests that at least in principle, you could extend modern-day calendars backwards and say "Yeah, the universe began on such-and-such a Friday in the Year Whatever, BCE." (In practice, of course, the information you'd need to do this might not be obtainable.)

Modern physics is nothing if not counterintuitive, though, so the above is quite possibly wrong. Anybody out there know?

Comments

( 5 comments — Leave a comment )
wcg
Oct. 23rd, 2009 02:37 pm (UTC)
While we have a pretty good idea of what was going on in the first few minutes, there's a big gap in knowledge after that. Wikipedia has a fairly decent timeline as it's currently understood. The earliest light that we can study, what we call the cosmic microwave background, comes from the recombination epoch when the universe was ~380,000 years old. To make things even more uncertain, we're not exactly sure how long ago the recombination epoch was from us.

My point is that right now we can give you the age of the universe to the nearest +/- hundred million years, but that's as close as an honest astronomer will get. When I first got into the astronomy biz back in the 70s we were saying it was somewhere between 10 and 20 billion years old, so you can see that we've made some progress on narrowing things down. The COBE and WMAP missions gave us the clues we needed to tighten things up to the canonical 13.7 billion year number that's all over the literature now. The Planck mission, currently doing its thing, may help us tighten things up a bit more via observations of the Sunyaev-Zeldovich effect, but of course that's still in the future. Even if the Planck mission succeeds beyond all expectations, we'll still have an uncertainty on the order of tens of millions of years in the age of the universe.
matt_ruff
Oct. 24th, 2009 07:31 pm (UTC)
Re: the uncertainty, what I was trying to get at with my question was which of the following was the case:

(a) We can't say exactly how old the universe is because we don't have enough information.

(b) The nature of time is such that the universe doesn't have an exact age.

From zarathud's answer, below, I see it's apparently (b).
wcg
Oct. 24th, 2009 11:37 pm (UTC)
Yes, (b) would figure strongly if we ever got to the point where we'd used up all the uncertainty caused by (a).
zarathud
Oct. 23rd, 2009 04:02 pm (UTC)
When you talk about cosmology, the principles of special and general relativity are fully in play. In particular, our notion of simultaneity is tossed out the window.

http://en.wikipedia.org/wiki/Relativity_of_simultaneity

Since there are so many different space-time trajectories from the big bang to us, there are many different answers for how long ago it was.

Sure, the universe's geometry isn't really that crazy, and one can make some arbitrary assumptions to get a coarse notion of time since the big bang, but I doubt it would be accurate or meaningful to within a day in the age of the universe
matt_ruff
Oct. 24th, 2009 07:10 pm (UTC)
Thanks, I suspected the answer would be something like this.
( 5 comments — Leave a comment )

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