How is the age of the Universe determined?

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Offline chris

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How is the age of the Universe determined?
« on: 26/06/2015 14:05:35 »
We are told that the Universe is 13.8 billion years old. But how is that determined? How do you date the Universe (apart from asking it out, of course!)?

I never forget a face, but in your case I'll make an exception - Groucho Marx

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Offline jccc

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Re: How is the age of the Universe determined?
« Reply #1 on: 05/07/2015 04:17:15 »
if we measure the red shift of star light, we can tell the distance.

from the distance we can measure the time needed for light to travel.

then we know the star is older than that time.

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Offline PmbPhy

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Re: How is the age of the Universe determined?
« Reply #2 on: 05/07/2015 08:57:57 »
We are told that the Universe is 13.8 billion years old. But how is that determined? How do you date the Universe (apart from asking it out, of course!)?
I think that we basically extrapolate the big bang back in time to when it was a point and figure out how long that took.

See: https://en.wikipedia.org/wiki/Age_of_the_universe

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Offline evan_au

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Re: How is the age of the Universe determined?
« Reply #3 on: 05/07/2015 14:47:11 »
By looking at the elemental composition of stars, and knowing the rate that these stars are burning their nuclear fuel, it is possible to spot some stars that are older than their neighbours, and this puts a lower limit on the age of the universe.