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Damien99

Basic astronomy

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Damien99

So took the advice of a few people was was watching basic astronomy video and sites. Something struck me as odd. 
 

so the estimate of the universe age is about 13 billion years old or so but it said we can see about 24-26 billions years of the universe. So how can we see that much but universe is half the age. 

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zep73

It's because, compared to the expansion at the big bang, light is very slow.
Light from the furthest objects apart, in the universe, will not reach each other until maybe in several billion years. Maybe never for some of them.
That's how incredibly huge the universe is.

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Damien99
3 minutes ago, sci-nerd said:

It's because, compared to the expansion at the big bang, light is very slow.
Light from the furthest objects apart, in the universe, will not reach each other until maybe in several billion years. Maybe never for some of them.
That's how incredibly huge the universe is.

But if we can see 26 billions years ago would that not mean universe is 26 billions years old and not 13 ish ´

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bison

Well, they presumably mean to say that since the universe expands in all directions, regardless your point of view, that this would account for about 26 billion years of expansion. 13 billion to your left, and 13 billion to your right.

The visible universe is reckoned to be about 93 billion light years in diameter. It can expand at a global speed greater than that of light, without violating relativity theory. It goes on expanding from every point of view within the three dimensional  universe, not just the point we happen to occupy. This adds to to the expansion.  

Edited by bison
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Damien99

How would that explain let say that galaxy they found 27 billions light years away then? If it’s 27 lights years away would that not mean universe been expanding 27 billions years, so how is it 13 b years old 

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zep73
29 minutes ago, Damien99 said:

How would that explain let say that galaxy they found 27 billions light years away then? If it’s 27 lights years away would that not mean universe been expanding 27 billions years, so how is it 13 b years old 

Like @bison (and common sense) said, the universe is estimated to be 93 billion light years in diameter. It is still growing. More rapidly every second.
Objects get further and further apart, so stars can move many light years away from each other, before they can see each other. That fact is considered when estimating distant stars.
Can you see now, how distance can easily get way longer than 13.8 billion light years?

Edited by sci-nerd
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Damien99
6 minutes ago, sci-nerd said:

Like @bison (and common sense) said, the universe is estimated to be 93 billion light years in diameter. It is still growing. More rapidly every second.
Objects get further and further apart, so stars can move many light years away from each other, before they can see each other. That fact is considered when estimating distant stars.
Can you see now, how distance can easily get way longer than 13.8 billion light years?

Yes but double the age of the universe?

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zep73
1 minute ago, Damien99 said:

Yes but double the age of the universe?

Not age. Distance!

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zep73

@Damien99 Shortly after the big bang, the universe was 200,000 light years in diameter, and growing very rapidly.

I found this video for you

 

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Piney
46 minutes ago, Damien99 said:

Yes but double the distance of the universe?

<--------13 billion LY----------YOU ARE HERE-----------13 billion LY---------->

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ChrLzs
57 minutes ago, Piney said:

<--------13 billion LY----------YOU ARE HERE-----------13 billion LY---------->

So... you mean Damien should ... LOOK BEHIND YOU!!!!  :D 

OK, I'm kidding, and we're going to confuse him further....  So, yeah, Damien it's a bit confusing, but as stated above, you first need to understand that a light year is a DISTANCE, and if you confuse that concept with the age of the Universe, it just doesn't work.

So the Universe is about 93 billion light-years across (but we're not really sure, as the tape measure ran out...).  That's all about DISTANCE.

But the age of the oldest stars we can see is about 13.7 billion years.  That's YEARS, ie a measure of time, not LIGHT-YEARS which is distance..
We guesstimate that age by looking at how the galaxies and stars are all mostly racing outwards, and then extrapolate that back to estimate when the BigBang happened (sort of)...

 

I know it's all the rage to learn stuff online, but if I was you Damien, I'd go to your local library (or your preferred Internet buying site) and get the book "Cosmos", by Carl Sagan.  Some of the info in it is a little out of date, but imo it's the best book ever written, and I don't just mean amongst astronomy books...

 

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Damien99

Thank you everyone

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