When younger, I learned the redshift explanation to resolve the paradox.
While I accept the newer explanation, I wonder:
If you assume an arbitrarily old (infinite age), steady-state universe, would redshift alone be enough to permit dark skies as we see them?
That has nothing to do with why right now, in our view, the sky is so dark. Right now, the starlight is blocked by dust, which is why even an area that actually is all stars, isn’t bright. While Olber (and many others) wo’ndered about the entire sky, it’s obvious that even the nearby areas that actually are solid stars don’t shine with the light of a solid mass of stars. Claiming the dust would glow as bright as the stars is the error.
Our finite-age Universe has dark skies. A universe of infinite age would not have dark skies. Therefore, we can say that the reason our skies are dark is because the Universe is of finite age.
I shudder to think of the textbooks you must have learned from. The correct answer has been known since the days of Edgar Allen Poe (who, yes, was the first person to give the explanation).
Are you being ironic? Is that a joke?
IIRC, it was an Asimov essay.
I think that you are saying, “No, redshift alone is not adequate.”
A paradox is a statement that contradicts itself or a situation which seems to defy logic. Olber’s paradox is created by assumptions, which is why it’s a paradox.
Partial quotation below
http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/cs_paradox.html
There is the essential paradox, along with the solution to it. Except Olber’s solution is rejected, which is where it gets complicated.
You see it there plainly. The assumption that obscuring dust would eventually heat up, and radiate the exact same energy, so even if dust was blocking the light, we would still be receiving the same amount of energy. This is simply not true at all. There is no evidence that the vast dust clouds blocking an extreme amount of starlight has heated up, and is radiating the same amount of light as it blocked.
It’s why I pointed out that both the Milky Way, as well as Andromeda are both regions of the dark sky that should be as bright and as hot as the sun, a solid mass of starlight, no darkness in between the stars at all in large areas of the sky. If the idea were true, that it can’t be dust reducing the light, because it would heat up and be just as bright as the stars it is blocking, then we would observe this.
Yet there is very little light seen, even the center of Andromeda, which is so thick with bright stars, there is no way to see through it, does not appear like a sun in the sky. Same for the center of the Milky Way, which is much much closer. With out dust blocking the light, it would be far brighter and hotter than the sun. If the dust heats up and shines as bright as the stars, we would still see this incredibly bright, and hot, galactic center in the sky.
Now obviously you can claim there hasn’t been enough time for the dust to heat up enough to glow brightly yet, but that does not change anything in regards to the dust being the cause of the dark sky.
In other words, our own galaxy isn’t subject to any red shift, and it doesn’t appear like a bright hot wall of stars, and it is quite close to us. It has to be the light years of dust shielding us from what would otherwise be a blinding hot mass of stars in the sky, day or night. Objecting to this by saying it can’t be dust dimming the light, or the dust would become as bright as the stars, is absurd, since we know it isn’t.
Certainly one could say it will be in the future, but that doesn’t change the facts of right now, in which it is obvious the Milky Way is dim, not bright as the sun.
FXMastermind as I said earlier in the thread the paradox is that observed reality doesn’t match what we would expect to see under the assumptions made. Under the assumptions made we would expect to see the interstellar dust heated to at least the temperature of the stars (the point being under the assumptions of the paradox there is enough time for the interstellar dust to heat up). Therefore the observation that the dust in our Universe is much cooler is simply part of the statement of the paradox and not its resolution.
This is a tricky question, after all; in an infinite, eternal, non-expanding universe, the stars would heat everything to a particular temperature, including themselves; the universe would be in thermal equilibrium. But this equilibrium will probably be hotter than the normal temperature of a red dwarf, which is the most common star in the sky; so the red dwarfs will heat up, expand - and therefore fuse more slowly. This heating would therefore slow down the average rate of fusion in the universe.
Ow- my head hurts.
Of course an eternal and infinite universe would need some cosmological mechanism to create new stars, when the old stars die and turn into white (or eventually black) dwarfs. There would also need to be a mechanism to remove the black dwarfs, and the abundance of metals they carry, as well.
No, that was not an assumption of the original paradox at all. Olber solved the original paradox by saying “the light is obscured by dust, that’s why the sky seems so dark”
It was after that conclusion that somebody claimed that the dust would heat up to the same temperature as the stars it was blocking, and we would still see and feel the exact same amount of energy, meaning the sky would still be completely bright and hot, like the sun appears. It doesn’t matter if you add “in an infinite universe over an infinite amount of time”, right now we do not observe this at all. So it does not counter his observation and conclusions at all. In any way.
A theoretical idea about what would happen “if the the Universe was …” does not counter the reality of what we now are experiencing, and that is a sky obscured by so much space dust that even the nearby galactic center is dark, rather than a blazing hot mass of stars.
It doesn’t matter what you claim about red shift, the age of the Universe, or any other theoretical idea, in reality right now, the sky is dark because far away stars (and everything else) is obscured by a huge amount of matter blocking out most of the radiation, including visible light.
This is quite simply incorrect.
That isn’t helpful at all. Why do you claim there is no dust obscuring the Milky Way?
I do not. You claim that this dust would not heat up in an infinite, eternal universe until it is in thermal equilibrium with the stars. Please explain why this would not happen.
FXMastermind, if we could surround our galaxy with a perfectly reflective sphere, what would the temperature of the dust in our galaxy be? Would it remain cooler than the stars, or be the same temperature as the stars?
No, you said that. I said that right now, the reason the Milky Way isn’t glowing bright, a solid mass of bright sky, is due to dust obscuring the starlight. Which is what Olber said was the reason the sky isn’t a solid mass of starlight.
Somebody claimed that couldn’t be so, because the dust would reach the same temperature as the stars, and we would still see a hot bright sky. That isn’t what we observe. The dust obscuring the Milky Way center, right now, hasn’t become as hot as the stars, which is why the Milky Way is dim.
If you disagree with that, please explain why.
Why do you think that ‘right now’ is important? In an infinite universe that has existed for ever, ‘right now’ would be the same as a trillion trillion years from now, and a trillion trillion years in the past. The dust will be at thermal equilibrium with the stars, and always will be, and always has been.
In an expanding, but infinite and eternal universe, the expansion of space time would change this situation drastically; at a certain distance from Earth the Universe would be expanding so much that it would be forever beyond our cosmic c-horizon, so no light could get here from there. This would also result in a dark sky.
One could ask the reverse, why is some other time important? The questions arose becuase “now” the sky looks dark, to us, where we are. Trying to figure out why that is so was the basis of the paradox. Olber solved the issue by explaining the stars are dim, because light is being blocked by dust. Right now, in the real Universe, our skies look dark because of dust blocking out the stars light.
Somebody (I can’t discover who actually says said this) declared Olber wrong, by claiming the dust would glow as bright as the stars. Eventually. I’m pointing out that while that may be theoretically true, and there is no evidence it is, but now, in the actual Universe we observe, it hasn’t happened. And so it it is indeed the reason a massive solid area of stars, like the center of our own Galaxy, does not appear as a bright solid area in the sky. In fact, it appears quite dim.
But that has nothing to do with now, and both our nearby Andromeda galaxy, or even more important, our own galactic center. They both appear dark, and there is no redshift involved. In fact, Andromeda and our own galaxy are moving towards each other.
If a theory/idea can’t explain the nearby dimming of starlight, there is no way to say it explains all the rest of the stars. Olber explained it all, with the simple and obvious reason. That somebody said he was wrong, doesn’t make it true. You have to be able to explain why nearby stars are so dark at night, to explain why the sky is dark. Not just stars very much farther away.
In fact, you have to explain why solid masses of stars, galactic centers, are so dark. Forget the idea that there may be a star in every bit of space we look at. Just look at the nearby area, the center of the Milky Way, where we know for a fact every bit of sky is filled with stars. And they aren’t that far away. Why isn’t that completely bright?
Houston, we have a problem. The assumption that there may be a star in every bit of space we look at is an** essential part of, and in fact is the heart of, the paradox**.
