Circular reasoning is circular?

[avevale_intelligencer]

Do we actually know that the universe is 13.7 billion years old on any other evidence than the fact that 13.7 billion light years (or thereabouts) is the furthest we can see, or is Professor Brian Cox (in the RT again) going round in educated circles here?

Comments

[legoline.livejournal.com]

I don't think that the universe is 13.7 billion years old because that means it "began" at some point. I don't think it ever began. I believe it has always been there, in whatever shape.

[aunty_marion]

I suspect the words 'at least' ought to be inserted before the numbers, to make things plausible. However, as you yourself have said: "Nothing can be proved one way nor t'other / neither would I be so bold."

[ci5rod.livejournal.com]

I believe the 3K microwave background radiation is the corroborating factor. It's at the right level for the big bang to have been 13.7 billion years ago.

[mdlbear]

Yes. It's basically because, when we look back 13.7 or so gigayears, what we see is the universe at the point where the big bang had cooled enough to become transparent to radiation.

[lexin.livejournal.com]

That's my understanding, too. Insofar as I understand it at all.

[catsittingstill.livejournal.com]

You might find this helpful. (http://en.wikipedia.org/wiki/Age_of_the_universe)

To summarize, it looks like the age of the universe can be approximated from several directions, which kind of suggests to me converging lines of evidence rather than circular reasoning.

[pbristow.livejournal.com]

Yep, that's it. We've gradually moved from a poition when we had one technique for estimating the age of the universe, and another for estimating the age of stars, and a massive contradiction between the too (some starts appeared to be older than the universe!), to now having several different approaches to meauring both things, which all roughly agree.

Note also that the phrase "the age of the universe" is slight shorthand for "the time that has passed since the point at which the physics of the early universe goes so haywire that it's currently impossible to give any meaningful picture of what happened before that, or even to be sure whether the term "before" has any useful meaning... But our simplest guess is it was only about another *this much* of a second. [HOLDS FINGERS SO CLOSE TOGETHER THAT BY ANY PRACTICAL MEASURE THEY ARE TOUCHING].

(Note also that the phrase "the time that has passed" does not even have so clear-cut a meaning as one might at first assume! =:o\ )