<p>Let me see if I can show why your "inverse-square-law means you can't get light from distant sources" intuition is wrong.</p>

<p>For the sake of argument let's assume stars really are point sources, and look at how much light you would receive from an infinitely old, infinitely large universe uniformly filled with point-source "stars", each with luminosity <span class="math-container">$L$</span>, at some finite density <span class="math-container">$\rho_{0}$</span> (# stars per cubic light year).</p>

<p>Imagine a thin spherical shell located at distance <span class="math-container">$D$</span>, with thickness <span class="math-container">$dD$</span> (small compared to <span class="math-container">$D$</span>). Each star in that shell will give you a flux of <span class="math-container">$L / (4 \pi D^{2})$</span> (there's your inverse-square law). How many stars are in that shell? That's just the volume of the shell -- approximately <span class="math-container">$4 \pi D^{2} dD$</span> -- times the density: <span class="math-container">$4 \pi D^{2} dD \rho_{0}$</span>.</p>

<p>Now consider a shell at twice the distance (<span class="math-container">$2 D$</span>). Each star in <em>that</em> shell contributes 1/4 the flux of a star in the first shell, since they're twice as far away. <strong>However</strong>, the volume of the thin shell is <em>four times larger</em> than the volume of the first shell (<span class="math-container">$4 \pi (2 D)^{2} dD = 16 \pi D^{2} dD$</span>, and so the number of stars in that shell is <em>four times larger</em>, which perfectly cancels out the decrease in flux. So the light coming from stars in that shell is the <em>same</em> as the light coming from stars in the first shell. Since there is an infinitude of such shells in the default infinite universe of the Paradox, and each shell contributes the same flux, the total flux you get from all the stars will be <em>infinite</em>.</p>

<p>Fortunately for the hypothetical inhabitants of that universe, the fact that stars are really finite in size prevents this from happening, since the finite disk of a star <em>blocks</em> light from all the stars directly behind it. But that means that wherever you look, your line of sight intersects with the surface of a star, which is the same as looking within the disk of the Sun.</p>

CC BY-SA 4.0
2020-02-01T20:22:01.433Z
Thank you for the post! I'm very grateful that you took the time to go over this interesting topic with me. Unfortunately, the shells and integral and everything else are just a formalized version of the paradox.
Jinny Ecckle
CC BY-SA 4.0
2020-02-01T20:22:06.750Z
The crux of the issue for me is that there are physical arrangements of stars with (instant light propagation) that won't yield the paradox. This means that the amount of EM energy (per unit v) in space would be totally governed by how the stars were arranged; which seems like a ridiculous physical interpretation. This, to me, suggests that something is wrong here. The way to address this is: Messing with the geometry and noting other factors like the first law of thermodynamics. If you're interested, there's a chat on stack physics where we'll be working on this. Thank you!
Jinny Ecckle
CC BY-SA 4.0
2020-02-01T20:30:54.167Z
BTW, I **never** said anything like ""inverse-square-law means you can't get light from distant sources,"" I said the amount you'd get is the finite answer to a particular  infinite sum....
Jinny Ecckle
CC BY-SA 4.0
2020-02-01T20:33:28.800Z
Would you mind taking that out of the quotation marks?
Jinny Ecckle
CC BY-SA 4.0
2020-02-01T15:23:49.463Z
2020-02-01T15:23:49.463Z
Peter Erwin
<p>The error I think you are making in your "logical" argument is "A light [ie a star] at a distance D1 would a appear as a point of light".  If D1 is a star, it would appear as a disc of light.  A very small disc, but a disc with a finite and nonzero size.</p>

<p>We then add stars at distance D2, D3 etc.  Each star covers more of the sky. This is because each star appears as a disc and not a point. Add infinitely many discs of light and you cover the whole sky.  </p>

<p>If in every direction that you look you see a disc of a star, then every direction is as bright as a star. This is the crux of the paradox.</p>

<p>The brightness of the star (as a point source) is irrelevant, so the argument from an "inverse square law" is a red herring.</p>

CC BY-SA 4.0
2020-01-30T21:19:04.857Z
Thank you for the answer. But, unfortunately, you made a few errors, 1. $D_n$ are  distances not a light. 2.  The shape disk, sphere, or point makes no difference; the issue at hand is the inverse square law, not the shape (there are no points in reality other than maybe black holes, anyway lol).
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:24:02.527Z
The significant issue here is that you just reaffirmed the paradox without really thinking about my Q. The thought experiment gives a finite sum, at least I think so. Really imagine spacing the lights like that, it should sum finite and small. Further, if you could really create this universe, as far as I can tell, it would act as I say. If not, please explain why?
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:28:14.143Z
"If the universe were infinitely old, infinite in space and homogenous then every line of sight would, end on a star, and the night sky would be a uniformly as bright as the sun." This is the issue, every line of sight would end on a star, of course, the issue is that I can't see any reason why the sky would be as bright 'as the sun.'
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:29:06.390Z
I would genuinely like to know how / why I'm wrong, but this isn't it. But thank you for taking the time!
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:32:21.400Z
No the thought experiment gives an infinte sum.  I've substantially edited.  The non-zero size of the stars is a key factor in this argument.
James K
CC BY-SA 4.0
2020-01-30T21:33:38.407Z
I know the sum is infinite, but the answer is finite, I think, to clarify.
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:35:48.457Z
The brightness is the key factor, if the star were dim enough, you wouldn't see it.
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:40:16.310Z
Oh, I see I misunderstood something you said. To start with, picture the lights in a line and then when that's clear, revolve them.
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:41:14.887Z
My question amounts to: If a line of lights won't create the paradox, why will some other arrangement?
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:51:30.717Z
I edited my post to clarify things, would you mind looking it over and then making an answer that takes account of what I'm really describing. Once more I am really thankful for your time!
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T21:53:25.890Z
You see, the thing I find, is that the 'paradox' is always upheld by sort of vague sweeping statements or assertions that it's true. But, when you look carefully at what might really happen these end up seeming flawed.
Jinny Ecckle
CC BY-SA 4.0
2020-01-30T22:35:34.337Z
Why is the inverse square law a red herring? In Olber's model all stars are the same size & absolute brightness, i.e., we have a homogeneous isotropic eternal universe populated by average stars. A star at unit distance occupies an angular area of $a$ with apparent brightness $L$, so its brightness per unit area is $L/a$. A star at distance $d$ occupies an area $a/d^2$ with brightness $L/d^2$ due to the inverse square law, so its brightness per unit area is once again $L/a$.
PM 2Ring
CC BY-SA 4.0
2020-01-30T23:05:46.077Z
"1. The brightness of nearer stars. 2. The fact that if far enough away it would simply be impossible to see." This is what's wrong.
ProfRob
CC BY-SA 4.0
2020-01-30T23:21:43.820Z
I think it's better to think of the photons the stars emit. If you've got an infinite universe of infinite age, even if each star emitted a single visible-light photon at low periodicity, an observer anywhere would still receive infinite photons. If a gas cloud or some other object obstructed a portion of the sky, that gas cloud would observe infinite photons exciting it and it would ionize and emit light itself.
BMF
CC BY-SA 4.0
2020-01-31T10:49:18.500Z
James we can sum points to get a distance. That is calculus. We don't need any angular size, the light could come from a point source and I guess the paradox *at the time of its formulation* would have been valid anyway  The key point is the wrong assumption as already pointed out in a comment above.
Alchimista
CC BY-SA 4.0
2020-01-31T18:46:40.090Z
@RobJeffries , What's wrong with "2." You can see this via: **1.** a pen flashlight with the reflector taken out. **2.** The fact that there are stars in the real universe that can't be seen with the naked eye.
Jinny Ecckle
CC BY-SA 4.0
2020-01-31T19:15:23.663Z
I can alse see the Milky Way without being able to see any individual star within it.
ProfRob
CC BY-SA 4.0
2020-02-01T13:55:47.540Z
The probable answer is actually quite simple:

Whilst space itself is infinite, matter is likely not.
White Prime
CC BY-SA 4.0
2020-02-02T11:52:10.870Z
A final remark from my side. No, nothing gets infinite in Olber paradox. You (the OP) correctly state that the light will sum up finite. And the Olber paradox says the same. The only infinite things there are an infinite universe and an infinite number of stars (because homogeneity). The sky does not get infinitely hot, its surface brightness would be that of the stars you sum up. If you have got something different, they were wrong and not formulating the paradox as it is.
Alchimista
CC BY-SA 4.0
2020-01-30T21:10:19.137Z
2020-01-30T21:33:49.123Z
2020-01-30T21:33:49.123Z
James K
<p>Ok, this is a bold question, I know. But, let me explain: After first hearing about <a href="https://en.wikipedia.org/wiki/Olbers%27_paradox" rel="nofollow noreferrer">Olbers' paradox</a>, I found that something seemed 'off' about it, so I looked into the subject as much as my skills (and time!) would allow. And I came to the conclusion that the paradox was probably kind of like Zeno's paradox: That is, something that 1., would not correspond to physical reality, 2., would not because some concept(s) was/were 'left out' during its formulation, in Zeno's case, the concepts of basic calculus.</p>

<p>Now, of course, I'm well aware of the fact that many of the best ideas in physics are counter-intuitive: General Relativity (and Special Relativity to a lesser degree, in my view), Quantum Physics, The Big Bang, even certain Elements of Thermodynamics, etc... However, Olbers' paradox doesn't seem problematic because of its counter-intuitiveness; but instead because it does not seem to me that it would happen in a steady-state, infinite, infinitely old version of our universe. Here are the reasons why:</p>

<p><strong>1. Logical / Mathematical:</strong></p>

<p>Lets invent the universe, lol. Well, a universe with an observer, and a light <span class="math-container">$D_1$</span> distance away such that the light source appears as a <strong>Small Disk</strong> of light. Now imagine adding another light source at twice <span class="math-container">$D_1$</span> away (retaining the same x, and z), <span class="math-container">$D_2$</span>, and then 3 times as far away (retaining the same x, and z), <span class="math-container">$D_3$</span>: And, so on, <span class="math-container">$D_1, D_2, D_3, D_4....$</span>, and so on forever. Given the  inverse square law, the observer would not see a field of view filled with light. They'd see the sum of the ever fainter lights, (<strong>The answer to which, not the sum itself</strong>) would be finite and pretty faint. And this shouldn't change, as far as I can tell, if they waited forever, or if 'god' copied and revolved these light sources around a range of axes, <strong>so long as there were a finite (not too big) number of near-by light sources.</strong></p>

<p><strong>2. Empirical:</strong></p>

<p>A lot of the light would become unseen for many reasons everyone here knows.</p>

<p>Alright, Olbers' paradox is unimportant today, as the universe isn't static or infinitely old. However, I think it shouldn't be presented as a sound idea if it is invalid.</p>

<p>So, I'd like for someone to explain to me, <strong>1.</strong> Why I'm wrong, or <strong>2.</strong> if I'm not wrong, why the paradox hasn't been examined more carefully.</p>

<p><strong>Notes For Answerers:</strong></p>

<p>Please note that people tend to answer questions like this by 'adding' stars of some brightness to the sky until the sky is super bright. This doesn't make sense as a star far enough away would be invisible to the naked eye due to: 1. The brightness of nearer stars. 2. The fact that if far enough away it would simply be impossible to see. In an "Olber Universe,' it seems that the sky 'around' the visible stars would seem dark to the human eye, but with tek you could 'find' a star anywhere you chose to look. </p>

CC BY-SA 4.0
2020-01-31T09:01:53.367Z
Olber's paradox fails to take into account many elements of the real universe: the age of the universe, the distribution of stars, the finite lifetime of stars, IGM absorption,... And I have never seen it presented as a sound idea, only as an historical anecdote.
usernumber
CC BY-SA 4.0
2020-01-31T09:29:33.327Z
"A lot of the light would become unseen for many reasons everyone here knows" is too vague to be a meaningful objection, so it's difficult to see how anyone can answer you in that context. You need to be more specific.
Peter Erwin
CC BY-SA 4.0
2020-01-31T10:58:07.023Z
@usernumber the "paradox" can be seen in the light of the xvii xviii centuries. As for the real major cause of a dark sky there are calculations even nowadays. One must to accept the premises (eternal static universe with an infinite number of stars) to appreciate the paradox. Ps I read that E. A. Poe was among the first writing down that perhaps all the light didn't yet had time to reach us, posing a kind of beginning
Alchimista
CC BY-SA 4.0
2020-01-31T13:03:38.990Z
Note that this question was [cross-posted to Physics.SE](https://physics.stackexchange.com/q/528205/123208), where it is now closed.
PM 2Ring
CC BY-SA 4.0
2020-01-31T18:23:03.910Z
@usernumber https://www.youtube.com/watch?v=gxJ4M7tyLRE
Jinny Ecckle
CC BY-SA 4.0
2020-02-02T08:06:29.560Z
Realise that there is much of nonsense in the question. In particular the paragraph titled Note for the answerers.
Alchimista
CC BY-SA 4.0
2020-02-02T08:09:49.530Z
@Alchimista, people seem to say so, but this subject appears engulfed in intellectual dishonesty, for some reason: The pattern: What I say is attacked, then specifics are asked for, and either the comments go away or no answer is given.
Jinny Ecckle
CC BY-SA 4.0
2020-02-02T08:12:21.643Z
Your assumption are incorrect. No one of the dishonest say point 1 and 2 in your notes.
Alchimista
CC BY-SA 4.0
2020-02-02T08:12:28.600Z
Don't get so attached to this ridiculous old 'paradox,' the universe is expanding anyhow, making the 'paradox' all the more silly. Of course, I may be wrong, still working that out; but making the 'paradox into a religion is of no use....
Jinny Ecckle
CC BY-SA 4.0
2020-02-02T08:13:17.150Z
@Alchimista You're not using standard English.
Jinny Ecckle
CC BY-SA 4.0
2020-02-02T08:14:13.833Z
@Alchimista Nevertheless, what's wrong with 1. and 2.? If there was something you'd come forth with it.
Jinny Ecckle
CC BY-SA 4.0
2020-02-02T08:17:21.723Z
@Alchimista, many people have had issues with 1., and 2., but I've not heard exactly what yet.
Jinny Ecckle
CC BY-SA 4.0
2020-02-02T08:40:20.240Z
Does my English really matters? Do you realise the poverty of your argument? You assume things on behalf of others then start discussing about. 1 both light from a bright source and a less brighter companion arrive to your eyes. If you can or not resolve the sources is a different story. 2. The distance issue must be treated within a homogenous and infinite universe. That is the main point of the "paradox". Light intensity goes as the inv sq but the number of sources goes as the sq. That is. I hope this can be read although written in non standard English.
Alchimista
CC BY-SA 4.0
2020-02-02T09:03:04.520Z
@Alchimista Don't feel bad; you probably speak English better than I do your native tongue.
Jinny Ecckle
CC BY-SA 4.0
2020-02-02T09:06:09.807Z
@Alchimista, that being said, I'll have to get back tomorrow as I'm having issues grasping what you're saying.
Jinny Ecckle
CC BY-SA 4.0
2020-02-02T09:47:45.227Z
I've also voted to close. I think the actual question can be asked more concisely now that there has been such an extensive exchange of comments. The beginning and ending are mostly self-indulgent or pushing a particular point of view. Can you boil this down to a clean, clear, crisp question, and at least make that separate from all of the other stuff? Thanks!
uhoh
<light><distances><big-bang-theory><parallax><visible-light>
Is Olbers' Paradox Nonsense?
Jinny Ecckle
# Is Olbers' Paradox Nonsense?

(Asked by: username_0 on 2020-01-30)

Ok, this is a bold question, I know. But, let me explain: After first hearing about [Olbers' paradox](https://en.wikipedia.org/wiki/Olbers%27_paradox), I found that something seemed 'off' about it, so I looked into the subject as much as my skills (and time!) would allow. And I came to the conclusion that the paradox was probably kind of like Zeno's paradox: That is, something that 1., would not correspond to physical reality, 2., would not because some concept(s) was/were 'left out' during its formulation, in Zeno's case, the concepts of basic calculus.

Now, of course, I'm well aware of the fact that many of the best ideas in physics are counter-intuitive: General Relativity (and Special Relativity to a lesser degree, in my view), Quantum Physics, The Big Bang, even certain Elements of Thermodynamics, etc... However, Olbers' paradox doesn't seem problematic because of its counter-intuitiveness; but instead because it does not seem to me that it would happen in a steady-state, infinite, infinitely old version of our universe. Here are the reasons why:

**1. Logical / Mathematical:**

Lets invent the universe, lol. Well, a universe with an observer, and a light $D\_1$ distance away such that the light source appears as a **Small Disk** of light. Now imagine adding another light source at twice $D\_1$ away (retaining the same x, and z), $D\_2$, and then 3 times as far away (retaining the same x, and z), $D\_3$: And, so on, $D\_1, D\_2, D\_3, D\_4....$, and so on forever. Given the inverse square law, the observer would not see a field of view filled with light. They'd see the sum of the ever fainter lights, (**The answer to which, not the sum itself**) would be finite and pretty faint. And this shouldn't change, as far as I can tell, if they waited forever, or if 'god' copied and revolved these light sources around a range of axes, **so long as there were a finite (not too big) number of near-by light sources.**

**2. Empirical:**

A lot of the light would become unseen for many reasons everyone here knows.

Alright, Olbers' paradox is unimportant today, as the universe isn't static or infinitely old. However, I think it shouldn't be presented as a sound idea if it is invalid.

So, I'd like for someone to explain to me, **1.** Why I'm wrong, or **2.** if I'm not wrong, why the paradox hasn't been examined more carefully.

**Notes For Answerers:**

Please note that people tend to answer questions like this by 'adding' stars of some brightness to the sky until the sky is super bright. This doesn't make sense as a star far enough away would be invisible to the naked eye due to: 1. The brightness of nearer stars. 2. The fact that if far enough away it would simply be impossible to see. In an "Olber Universe,' it seems that the sky 'around' the visible stars would seem dark to the human eye, but with tek you could 'find' a star anywhere you chose to look.

**Tags:** light, distances, big-bang-theory, parallax, visible-light

> **Comments:**
> **username_1**: Olber's paradox fails to take into account many elements of the real universe: the age of the universe, the distribution of stars, the finite lifetime of stars, IGM absorption,... And I have never seen it presented as a sound idea, only as an historical anecdote.  
> **username_2**: "A lot of the light would become unseen for many reasons everyone here knows" is too vague to be a meaningful objection, so it's difficult to see how anyone can answer you in that context. You need to be more specific.  
> **username_3**: @username_1 the "paradox" can be seen in the light of the xvii xviii centuries. As for the real major cause of a dark sky there are calculations even nowadays. One must to accept the premises (eternal static universe with an infinite number of stars) to appreciate the paradox. Ps I read that E. A. Poe was among the first writing down that perhaps all the light didn't yet had time to reach us, posing a kind of beginning  
> **username_4**: Note that this question was [cross-posted to Physics.SE](https://physics.stackexchange.com/q/528205/123208), where it is now closed.  
> **username_0**: @username_1 https://www.youtube.com/watch?v=gxJ4M7tyLRE  
> **username_3**: Realise that there is much of nonsense in the question. In particular the paragraph titled Note for the answerers.  
> **username_0**: @username_3, people seem to say so, but this subject appears engulfed in intellectual dishonesty, for some reason: The pattern: What I say is attacked, then specifics are asked for, and either the comments go away or no answer is given.  
> **username_3**: Your assumption are incorrect. No one of the dishonest say point 1 and 2 in your notes.  
> **username_0**: Don't get so attached to this ridiculous old 'paradox,' the universe is expanding anyhow, making the 'paradox' all the more silly. Of course, I may be wrong, still working that out; but making the 'paradox into a religion is of no use....  
> **username_0**: @username_3 You're not using standard English.  
> **username_0**: @username_3 Nevertheless, what's wrong with 1. and 2.? If there was something you'd come forth with it.  
> **username_0**: @username_3, many people have had issues with 1., and 2., but I've not heard exactly what yet.  
> **username_3**: Does my English really matters? Do you realise the poverty of your argument? You assume things on behalf of others then start discussing about. 1 both light from a bright source and a less brighter companion arrive to your eyes. If you can or not resolve the sources is a different story. 2. The distance issue must be treated within a homogenous and infinite universe. That is the main point of the "paradox". Light intensity goes as the inv sq but the number of sources goes as the sq. That is. I hope this can be read although written in non standard English.  
> **username_0**: @username_3 Don't feel bad; you probably speak English better than I do your native tongue.  
> **username_0**: @username_3, that being said, I'll have to get back tomorrow as I'm having issues grasping what you're saying.  
> **username_5**: I've also voted to close. I think the actual question can be asked more concisely now that there has been such an extensive exchange of comments. The beginning and ending are mostly self-indulgent or pushing a particular point of view. Can you boil this down to a clean, clear, crisp question, and at least make that separate from all of the other stuff? Thanks!  

---

## 2 answers

### Answer by username_2 on 2020-02-01. Score: 4

Let me see if I can show why your "inverse-square-law means you can't get light from distant sources" intuition is wrong.

For the sake of argument let's assume stars really are point sources, and look at how much light you would receive from an infinitely old, infinitely large universe uniformly filled with point-source "stars", each with luminosity $L$, at some finite density $\rho\_{0}$ (# stars per cubic light year).

Imagine a thin spherical shell located at distance $D$, with thickness $dD$ (small compared to $D$). Each star in that shell will give you a flux of $L / (4 \pi D^{2})$ (there's your inverse-square law). How many stars are in that shell? That's just the volume of the shell -- approximately $4 \pi D^{2} dD$ -- times the density: $4 \pi D^{2} dD \rho\_{0}$.

Now consider a shell at twice the distance ($2 D$). Each star in *that* shell contributes 1/4 the flux of a star in the first shell, since they're twice as far away. **However**, the volume of the thin shell is *four times larger* than the volume of the first shell ($4 \pi (2 D)^{2} dD = 16 \pi D^{2} dD$, and so the number of stars in that shell is *four times larger*, which perfectly cancels out the decrease in flux. So the light coming from stars in that shell is the *same* as the light coming from stars in the first shell. Since there is an infinitude of such shells in the default infinite universe of the Paradox, and each shell contributes the same flux, the total flux you get from all the stars will be *infinite*.

Fortunately for the hypothetical inhabitants of that universe, the fact that stars are really finite in size prevents this from happening, since the finite disk of a star *blocks* light from all the stars directly behind it. But that means that wherever you look, your line of sight intersects with the surface of a star, which is the same as looking within the disk of the Sun.

> **Comments:**
> **username_0**: Thank you for the post! I'm very grateful that you took the time to go over this interesting topic with me. Unfortunately, the shells and integral and everything else are just a formalized version of the paradox.  
> **username_0**: The crux of the issue for me is that there are physical arrangements of stars with (instant light propagation) that won't yield the paradox. This means that the amount of EM energy (per unit v) in space would be totally governed by how the stars were arranged; which seems like a ridiculous physical interpretation. This, to me, suggests that something is wrong here. The way to address this is: Messing with the geometry and noting other factors like the first law of thermodynamics. If you're interested, there's a chat on stack physics where we'll be working on this. Thank you!  
> **username_0**: BTW, I **never** said anything like ""inverse-square-law means you can't get light from distant sources,"" I said the amount you'd get is the finite answer to a particular  infinite sum....  
> **username_0**: Would you mind taking that out of the quotation marks?  

---

### Answer by username_6 on 2020-01-30. Score: 1

The error I think you are making in your "logical" argument is "A light [ie a star] at a distance D1 would a appear as a point of light". If D1 is a star, it would appear as a disc of light. A very small disc, but a disc with a finite and nonzero size.

We then add stars at distance D2, D3 etc. Each star covers more of the sky. This is because each star appears as a disc and not a point. Add infinitely many discs of light and you cover the whole sky.

If in every direction that you look you see a disc of a star, then every direction is as bright as a star. This is the crux of the paradox.

The brightness of the star (as a point source) is irrelevant, so the argument from an "inverse square law" is a red herring.

> **Comments:**
> **username_0**: Thank you for the answer. But, unfortunately, you made a few errors, 1. $D_n$ are  distances not a light. 2.  The shape disk, sphere, or point makes no difference; the issue at hand is the inverse square law, not the shape (there are no points in reality other than maybe black holes, anyway lol).  
> **username_0**: The significant issue here is that you just reaffirmed the paradox without really thinking about my Q. The thought experiment gives a finite sum, at least I think so. Really imagine spacing the lights like that, it should sum finite and small. Further, if you could really create this universe, as far as I can tell, it would act as I say. If not, please explain why?  
> **username_0**: "If the universe were infinitely old, infinite in space and homogenous then every line of sight would, end on a star, and the night sky would be a uniformly as bright as the sun." This is the issue, every line of sight would end on a star, of course, the issue is that I can't see any reason why the sky would be as bright 'as the sun.'  
> **username_0**: I would genuinely like to know how / why I'm wrong, but this isn't it. But thank you for taking the time!  
> **username_6**: No the thought experiment gives an infinte sum.  I've substantially edited.  The non-zero size of the stars is a key factor in this argument.  
> **username_0**: I know the sum is infinite, but the answer is finite, I think, to clarify.  
> **username_0**: The brightness is the key factor, if the star were dim enough, you wouldn't see it.  
> **username_0**: Oh, I see I misunderstood something you said. To start with, picture the lights in a line and then when that's clear, revolve them.  
> **username_0**: My question amounts to: If a line of lights won't create the paradox, why will some other arrangement?  
> **username_0**: I edited my post to clarify things, would you mind looking it over and then making an answer that takes account of what I'm really describing. Once more I am really thankful for your time!  
> **username_0**: You see, the thing I find, is that the 'paradox' is always upheld by sort of vague sweeping statements or assertions that it's true. But, when you look carefully at what might really happen these end up seeming flawed.  
> **username_4**: Why is the inverse square law a red herring? In Olber's model all stars are the same size & absolute brightness, i.e., we have a homogeneous isotropic eternal universe populated by average stars. A star at unit distance occupies an angular area of $a$ with apparent brightness $L$, so its brightness per unit area is $L/a$. A star at distance $d$ occupies an area $a/d^2$ with brightness $L/d^2$ due to the inverse square law, so its brightness per unit area is once again $L/a$.  
> **username_7**: "1. The brightness of nearer stars. 2. The fact that if far enough away it would simply be impossible to see." This is what's wrong.  
> **username_8**: I think it's better to think of the photons the stars emit. If you've got an infinite universe of infinite age, even if each star emitted a single visible-light photon at low periodicity, an observer anywhere would still receive infinite photons. If a gas cloud or some other object obstructed a portion of the sky, that gas cloud would observe infinite photons exciting it and it would ionize and emit light itself.  
> **username_3**: username_6 we can sum points to get a distance. That is calculus. We don't need any angular size, the light could come from a point source and I guess the paradox *at the time of its formulation* would have been valid anyway  The key point is the wrong assumption as already pointed out in a comment above.  
> **username_0**: @RobJeffries , What's wrong with "2." You can see this via: **1.** a pen flashlight with the reflector taken out. **2.** The fact that there are stars in the real universe that can't be seen with the naked eye.  
> **username_7**: I can alse see the Milky Way without being able to see any individual star within it.  
> **username_9**: The probable answer is actually quite simple:  Whilst space itself is infinite, matter is likely not.  
> **username_3**: A final remark from my side. No, nothing gets infinite in Olber paradox. You (the OP) correctly state that the light will sum up finite. And the Olber paradox says the same. The only infinite things there are an infinite universe and an infinite number of stars (because homogeneity). The sky does not get infinitely hot, its surface brightness would be that of the stars you sum up. If you have got something different, they were wrong and not formulating the paradox as it is.  

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