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Olbers' Paradox

en.wikipedia.org

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Re: Olbers' Paradox

#11

Post by bmn__ »

pingpongrandom wrote: post #2

Cool concept, but doesn't consider planets, or nebulae, or other space objects that can block light. I have no expertise to speak with authority on this, so please, weigh in on this consideration. But wouldn't this break the "homogeneity" assumption? EDIT: Thinking about this further, could you make approximation rules about the things that block light, too? e.g. By the nature of a star's mass, you can assume that so…

> but doesn't consider planets, or nebulae, or other space objects that can block light

This is addressed in the article. ctrl+f cloud

Re: Olbers' Paradox

#13

Post by bckr »

nusaru wrote: post #12

So basically, we don't exactly know why the night sky is mostly dark? (At least, that's what I got out of this)

> The darkness of the night sky is one of the pieces of evidence for a dynamic universe, such as the Big Bang model. That model explains the observed non-uniformity of brightness by invoking spacetime's expansion, which lengthens the light originating from the Big Bang to microwave levels via a process known as redshift; this microwave radiation background has wavelengths much longer than those of visible light, and so appears dark to the naked eye.

Re: Olbers' Paradox

#14

Post by nusaru »

bckr wrote: post #13
nusaru wrote: post #12

So basically, we don't exactly know why the night sky is mostly dark? (At least, that's what I got out of this)

> The darkness of the night sky is one of the pieces of evidence for a dynamic universe, such as the Big Bang model. That model explains the observed non-uniformity of brightness by invoking spacetime's expansion, which lengthens the light originating from the Big Bang to microwave levels via a process known as redshift; this microwave radiation background has wavelengths much longer than those of visible light, and…

> The redshift hypothesised in the Big Bang model [...]

Doesn't sound to me like it's more than a hypothesis, but I could be wrong.

Re: Olbers' Paradox

#15

Post by mhh__ »

pingpongrandom wrote: post #2

Cool concept, but doesn't consider planets, or nebulae, or other space objects that can block light. I have no expertise to speak with authority on this, so please, weigh in on this consideration. But wouldn't this break the "homogeneity" assumption? EDIT: Thinking about this further, could you make approximation rules about the things that block light, too? e.g. By the nature of a star's mass, you can assume that so…

If you imagine a curve of the light from a star, the dip in the curve from a planet passing in between us and the star is actually relatively small. They don't block that much light (and what they do block heats the planet, which in turn will radiate lower energy light)

Re: Olbers' Paradox

#17

Post by AnotherGoodName »

nusaru wrote: post #14
bckr wrote: post #13

Earlier quoted context omitted.

> The darkness of the night sky is one of the pieces of evidence for a dynamic universe, such as the Big Bang model. That model explains the observed non-uniformity of brightness by invoking spacetime's expansion, which lengthens the light originating from the Big Bang to microwave levels via a process known as redshift; this microwave radiation background has wavelengths much longer than those of visible light, and…

> The redshift hypothesised in the Big Bang model [...] Doesn't sound to me like it's more than a hypothesis, but I could be wrong.

Well redshift alone explains the paradox. You don't even need to accept the big bang theory. You can just say "stars that are further away are more redshifted" and that alone explains this. Which we know is true. That's not a hypothesis, redshift can be observed directly. And that fact alone explains the apparent paradox. The most distant stars are redshifted away.

To quote the above article

>The redshift hypothesised in the Big Bang model would by itself explain the darkness of the night sky even if the universe were infinitely old.

Redshift is what explains this. There could be different explanations for the redshift but redshift is 100% an observed phenomena.

Re: Olbers' Paradox

#19

Post by trhway »

thechao wrote: post #4
pingpongrandom wrote: post #2

Cool concept, but doesn't consider planets, or nebulae, or other space objects that can block light. I have no expertise to speak with authority on this, so please, weigh in on this consideration. But wouldn't this break the "homogeneity" assumption? EDIT: Thinking about this further, could you make approximation rules about the things that block light, too? e.g. By the nature of a star's mass, you can assume that so…

There's no "blocking light": anything that "blocks light" would get hot from absorbing that light and, then, reradiate. By this time (some point along the curve of "infinitely old universe") everything should be radiating a lot.

Or the energy may get captured and stored as chemical for example.

Re: Olbers' Paradox

#20

Post by vikingerik »

WinterMount223 wrote: post #9
AdamH12113 wrote: post #7

A more concise explanation can be found in the Usenet Physics FAQ: https://math.ucr.edu/home/baez/physics/Relativity/GR/olbers....

> too. It does act like a radiation shield, exponentially damping the distant starlight. This is wrong, damping is not exponential but to the fourth root.

A root is a fractional exponent; I can see that as a valid description.
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