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Author Topic: Why is the night sky not white?  (Read 2805 times)

Offline colin thrower

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Why is the night sky not white?
« on: 09/07/2010 18:30:02 »
colin thrower  asked the Naked Scientists:
   
Hello Chris

When we look at the clear night sky, why are we only seeing a certain
number of stars....what I mean is if, as I believe, the universe has
always been there, then the light from all the billions of stars out
there will have had time to reach us, so the night sky should be a
brilliant white, should it not?

I have lots of theories
That they are moving away beyond the speed of light
That there are black holes in between
That their light has dissipated
That many billions of them are fading

For that matter, why does any starlight reach us at all?  After all,
sound quickly fades over very short distances.

Thanks in advance

Colin Thrower

What do you think?
« Last Edit: 09/07/2010 18:30:02 by _system »


 

Online syhprum

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Why is the night sky not white?
« Reply #1 on: 09/07/2010 19:07:57 »
The night sky is not free of electromagnetic radiation but due to the finite age of the universe and its continual expansion the the energy is redshifted down to an equivalent temperature of 2.7K that we recognize as the CMBR

http://en.wikipedia.org/wiki/Olbers'_paradox
 

Offline Murchie85

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Why is the night sky not white?
« Reply #2 on: 09/07/2010 22:01:51 »
Only light from 14 billion years ago has reached us so far, if there is anything further away than that then its light has not yet reached us and therefore has not yet been observed.
 

Offline Stefanb

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Why is the night sky not white?
« Reply #3 on: 14/07/2010 05:44:59 »
If the universe has, as you say, "always been there", then the skuy would perhaps be Moor wheite, unless, as you also sugjested, black wholes were in the whey. However, the outward movement of many stars and galaxies would eventually push all light so far out that the speck it created (as we on earth could see it) would be diminutive. It all depends, really, on how many stars there are, and how close they are to us.
 

Offline Bored chemist

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Why is the night sky not white?
« Reply #4 on: 14/07/2010 07:00:43 »
You are not the first to wonder about this.
http://en.wikipedia.org/wiki/Olbers'_paradox
The thing I don't understand is how come you see the dark sky at night yet you ignore this evidence and say  "as I believe, the universe has always been there".
Moving faster than the speed of light doesn't work as an explanation.
There would need to be an infinite number of black holes so the universe would collapse under their gravity.
Where would the light dissipate to?
Billions of what are fading?
 

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Why is the night sky not white?
« Reply #4 on: 14/07/2010 07:00:43 »

 

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