So, you’re saying that a patch of sky much bigger than the full moon being as bright as the full moon is equivalent to every square milliarcsecond of the sky being filled with the surface of a star?
No, it doesn’t say that. It says the combined light of all the stars located toward the galaxy’s core. The galactic core is massive, and covers several square degrees in the sky. The Moon, on the other hand, covers a small fraction of a square degree.
So even if the galactic core plus all the other stars shone as brightly as the full Moon, each square degree would be much dimmer than the full Moon.
The dispute is not over the brightness of 200 billion stars, it’s over the assumption that dust isn’t obscuring them.
It doesn’t matter if you add on “if the universe were infinite and eternal”, that has nothing to do with the here and now, where the Milky Way is not bright, when it should be.
http://www.straightdope.com/columns/read/1356/why-is-the-night-sky-dark
“The dust would absorb so much light it’d eventually start glowing itself.”
I clearly stated that part is wrong. If it weretrue , the dust obscuring the nearby mass of hundreds of billions of stars should glow brighter than the full moon. The dust and the stars are almost as old as the Universe. The dust doesn’t glow as bright as the stars.
It’s an assumption somebody made, but what we observe does not match. There isn’t any part of the Milky Way that we can see, where obscuring dust glows brightly, like starlight. We can check this looking at Andromeda as well. It’s 300, maybe 400 billion stars (estimated), with a huge center. The center should glow bright like a star, but it doesn’t.
While appearing much smaller than the Milky Way core, it should still be quite bright. But it is very dim instead. Returning to the explanation.
http://www.straightdope.com/columns/read/1356/why-is-the-night-sky-dark
That may be true, but it doesn’t explain why the regions of the sky that are full of stars (or very nearly so, we don’t actually know), also appear dark. Not a mass of glowing starlight. It’s the dust.
To make it real simple. If there were 200 billion stars not obscured by dust, and they were near us (like in our Milky Way) the sky would not appear dark when looking at them. In fact, it would be much brighter than a full moon out. We can only see a small fraction of the stars looking towards our own galaxies center. If dust were not blocking the light, it would be very bright. The dust does not glow as bright as the star light it blocks.
The question isn’t “why isn’t the night sky as bright as it is when there’s a full moon?”. The question is “why isn’t the entire night sky blazing with the light of the Sun?”.
No, it’s “if the Universe is infinite, then why doesn’t every last point we observe have a star visible?”
Yes.
It does.
The dust absorbs the light and re-radiates it. Because there is so little light from the galaxy (only a full-moon’s worth, at most) it re-radiates it at a low temperature. The luminosity of the dust is the same as the stars it conceals, except at a different wavelength.
If the luminosity of the dust were not the same as the stars inside it, the dust would heat up until it was.
Given an infinite and eternal, non-expanding universe, the amount of light re-radiated would equal the incident light, so the dust would be as hot (and as bright) as a star.
FXMastermind pointed at this ongoing discussion in a GD thread.
Did FX just dissed [del]Cuthulu[/del] Cecil? 
As the Bad Astronomer points out there are still better explanations other than just dust:
http://blogs.discovermagazine.com/badastronomy/2012/10/01/why-is-the-sky-dark-at-night/
A more detailed explanation can be found here by John Carlos Baez, American mathematical physicist and a professor of mathematics at the University of California, Riverside in Riverside.
You switched from brightness to luminosity.
The assumption that was used to declare Olbers wrong, was that the dust would glow as brightly as the star light it blocked. Not "the dust will re-radiate the star light as infrared, which we can’t see, so the sky will seem dark ". If that is the reasoning, it means Olbers was right, when he decided it was dust blocking the light from distant stars.
Olbers was explaining why a sky full of stars (an infinite number) wouldn’t appear bright. If the sky was indeed a star in every last point of space, it wouldn’t be bright. Because of what we know from our own galaxy. The dust blocks the light.
I didn’t see your post before my previous post. The dust is being discussed because it does block our own galaxies light, but doesn’t glow brightly, like the stars it is hiding from sight.
This is just an observation of reality, as it appears in our sky, right now.
Certainly the galactic center of our Milky Way would be a very bright thing except for the dust. Remember we can only see 6000 light years towards the core. It’s maybe 25,000 light years away. There is no doubt that right now, there is no evidence that dust that blocks stars ever glows as bright as the stars.
Olbers was wrong. If the sky was full of stars then the dust would absorb the heat and re-radiate it at the same temperature, because there would be nowhere for the heat to go. You can only radiate the heat into a dark sky; if you try to radiate into a bright sky the flux inwards will be the same as the flux outward.
Still wrong, no matter how many times you say it.
The brightest estimate you have found so far is that the entire centre of the galaxy would be as bright as the Full Moon, if there were no dust; the galactic bulge subtends an area about 25° × 10°, whereas the Moon is only half a degree across. Each square degree would shine with about 1/500th the brightness of the Moon, assuming no dust.
Not enough dust, and it does not explain why in the many more areas of the observable universe outside the galactic plane, with less dust, is that we cannot see more stars.
As I see what they are teaching currently in universities about Astronomy, I do not think this dust theory can hold a candle to what Edgar Alan Poe realized just by intuition, before Hubble and others could explain it scientifically:
You are required to provide the source when you quote somebody.
https://www.e-education.psu.edu/astro801/content/l10_p2.html
That claim is even easier to debunk. The nearby Andromeda Galaxy isn’t bright. In fact, if the entire sky was filled with galaxies that close, the sky would still seem dark.
You are talking about the actual issue of the number of galaxies we can see (because outside of our galaxy, you won’t ever see a regular star).
That isn’t the question about the dust. Both the Milky Way and the Andromeda galaxy do not appear bright, nor does the obscuring dust glow like star light.
How bright do you think the Andromeda Galaxy would be if there were no dust obscuring its light? If it has 400 billion stars, with an average brightness similar to the Sun, and assuming no dust, the total brightness turns out to be mag. 0.2, about the same as Rigel.
In fact, because the Andromeda Galaxy is turned sideways on to us, the dust inside it does not obscure the light of its stars very efficiently. Dust is not sufficient to explain the obscuration of galaxies.
This is the same thing as what I said. If every last point we observed had a star visible, then the entire sky would blaze like the surface of the Sun.
Indeed, and I have to apologize for forgetting the source, in any case, FX pointed at it but he is missing another point, almost all the experts and academics do not agree with him. As usual.
No, that isn’t what the article said.
EarthSky | What the center of the galaxy looks like
That is exactly what my point about dust was about. First, if there were no blocking dust, the sky would be much much brighter, just looking towards the core would be brighter than the full moon. (the rest of the galaxy, especially the stars closer to us, would be much brighter as well)
Second, even with the dust and stars being almost as old as the Universe, there is no dust blocking out the stars, glowing as bright as stars.
Herschel dismissed the very idea that dust could be a reason for the sky to be dark, and I am showing that reality does not match this.
You change the goal post to “in an infinite Universe with infinite stars it would”, and I say from the view of reality, that does not mean what I pointed out is wrong. In reality, dust is exactly why the areas of our sky, that we know are almost a solid mass of stars, (like the paradox deal with), doesn’t glow brightly. And dust is the reason. And the dust does not heat up and glow as bright as starlight.
The paradox may very well be resolved by the fact there isn’t an infinite Universe, and there aren’t enough stars, and the redshift dims distant galaxies, but none of that changes the facts about obscuring dust. If there actually were a solid sky of galaxies, no redshift, the sky were solid stars, like Andromeda and the Milky way, in every last direction we can see, it would still look dark. Just as the Milky Way and Andromeda look dark, in the actual real sky at night.
A sky lit by the equivalent of a full moon is still a night sky, and it’s still by most standards dark. It is not even remotely similar to a sky blazing with the fire of the Sun, which is what Olber’s paradox is about.
And if that did not screw you people up I will mention and you will agree when you to discover what sound really is, is that sound is much faster than light.
PS - my education is grade eight, nine if they had not failed me!