Friar Bellows

In fact, interstellar dust is not even a minor reason. Dust in such a hypothetical universe would simply re-radiate the energy it absorbed, and everything would still be hot and bright. The major reason the night sky is dark is ... well, it's an interplay of various factors. The ones I would call "major factors" are the finite lifetimes of stars, the finite age of the universe, and the average number density of stars. Cosmological redshift I would place somewhere between major and minor. The rest are either minor or have no effect at all.

HeatherD

Did no one bother to read the links I posted on Olbers' Paradox? They explain all the reasons why the night sky isn't lit up with the light of trillions of stars.

Sorry to sound so bitchy, but if no one is going to read informational posts that I've gone to the trouble of researching, I won't bother in the future.

Asha'man

Yea, I read them. However, I suspect that you are right about others not reading them. You might find that your links get more attention if you selectively quote a few key sentances, so that people know what the point is.

Friar Bellows

What makes you think that?

The Scientific American link correctly identifies the two effects that are the most important. Unfortunately it doesn't properly deal with redshift, which is a small but not negligible effect. Indeed, to my amateur eyes, the following paragraph seems entirely wrong:

I thought it did happen. Perhaps one of our regulars, Shadowy Man (who is an astrophysicist), can set my mind at rest.

The Wolfram link applies the paradox not to our universe (or our currently accepted model of the universe), but to a hypothetical universe: "an infinite, static, Euclidean space". Our universe may or may not be infinite, but the evidence strongly suggests it is not static or Euclidean. So, the answers given on the Wolfram site do not necessarily apply to our universe. Indeed, only one of them, answer 2, is known to have an effect.

The two links on the Scientific American site, are very good, though. I'll put them here for the benefit of those who are interested:

http://math.ucr.edu/home/baez/physic...GR/olbers.html
http://zebu.uoregon.edu/~imamura/123...-5/olbers.html

The first link has a reference to the definitive paper on the subject (well, until evidence turns up to change our understanding). Here's a link to it:

http://adsabs.harvard.edu/cgi-bin/np...99W&db_key=AST

To be perfectly honest, it does sound a bit bitchy, especially when you don't really know if no one read your post.

Shadowy Man

Uh yes... it does happen. (I don't know what Karen Kwitter was trying to say. She's not an ultraviolet or high-redshift astronomer, but she should still know better.)

In fact, high redshift quasars are identified by their ultraviolet spectra, as observed at visible wavelengths from the ground.

There will be a lot less light available from the ultraviolet redshifted down because interstellar and intergalactic hydrogen will absorb most of it (shortward of 91.2 nanometers) until you get out toward x-ray wavelengths.