In astrophysics and physical cosmology, Olbers’ paradox, is the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. It is one of the pieces of evidence for a non-static universe such as the current Big Bang model. The argument is also referred to as the “dark night sky paradox” (see physical paradox).

Much more here. I love wikipedia!

I remember that this really puzzled me when I was a kid, that is, why the night sky looked the way it did (Olbers’ paradox actually isn’t a good place to start if you want to know that, but anyway…). I didn’t get why, if there was a lot of stars around in the sky, lighting up everything, then even if the universe was very large and the stars were far away, why was everything so dark at night? If there was a star in almost every direction I could see, then why wasn’t the sky much brigther? Also, if the universe was infinitely large (I had a really difficult time accepting that statement), then there would be an infinite number of stars too, rigth (no, that’s not right, see point a in the link. But I didn’t get that back then of course)? And if there was an infinite number of stars, they would light up the whole sky, not just bits and pieces here and there, rigth? Asking my parents didn’t really help… (I’m pretty sure it was during my “asking age” I wondered about this, that period of your life where you drive your parents insane by asking them so many questions that no human being can possibly answer all of them, but I’m also quite sure it took me a long time to pass that age, so that doesn’t really help me pinpoint the exact time).

Btw: If you were wondering, the number of stars visible with the naked eye at night-time at any given location on earth, given ideal viewing conditions, is in the neighbourhood of 3.000, as Asimov expressed it in his book Facts and Fancy (recommended): The faintest star that can be seen with the naked eye, under the best conditions, is of magnitude 6.5 and the number of stars that exist in the entire circuit of the skies that bright or brighter is just about 6000. That’s all. That’s the hard fact of it. Six thousand.

For comparison, it is estimated that the total number of stars in the observable universe is 7×10^22.


May 25, 2009 - Posted by | Astronomy, cosmology, Random stuff

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