<p>OK, Imagine the stars at distance x block an area of the sky. At a distance of 2x there should be four times as many stars, but they would seem four times smaller in terms of area covered. Thus, the blocking grows linearly until a significant part of the sky is blocked. The stars within 20 light years (excluding the Sun), blocks approximately $4.3 \cdot 10^{-16}$ of the sky. Even if we scale that up to the radius of the universe, 45 billion light years, only about $2 \cdot 10^{-6}$ of the sky is covered.</p>

<p>Even that tiny number is an overestimate, as we live in an extremely star-dense part of the universe, our galaxy.</p>

<p>Space is simply too big.</p>

CC BY-SA 3.0
2016-02-14T14:41:50.520Z
Great answer, but where do you have the $3\times10^{-19}$ from?
pela
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2016-02-14T14:56:30.700Z
@pela It is calculated from the catalogue of stars within 21 light years http://www.johnstonsarchive.net/astro/nearstar.html , using an average radius. It may not be exact or representative in any way, and therefore deviate with at least one order of magnitude. But even then the conclusion holds.
SE - stop firing the good guys
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2016-02-14T17:26:13.507Z
@RobJeffries One can apparently not be careful enough with data. Manually checking the result of my table look-up, I found an error. The RMS stellar radius is 0.55 of the Sun and the representative distance 15 ly. The correct fraction is then $4.3 \cdot 10^{-16}$. Sorry about the previous error.
SE - stop firing the good guys
CC BY-SA 3.0
2016-02-14T10:10:43.457Z
2016-02-14T17:27:14.057Z
2016-02-14T17:27:14.057Z
SE - stop firing the good guys
<p>I know that we are able to "see back into time" by looking very far away through telescopes such as the Hubble telescope, but my question is, wouldn't you run into at least a couple of stars that were blocking your vision when you were trying to look even farther? </p>

<p>Imagine a big Boulder in front of another smaller Boulder  and if we are looking from the side of the larger Boulder, we wouldn't be able to see the smaller one because the bigger one was in the way. Hopefully that simplifies my question. If it is as simple as that, wouldn't we miss stars and not be able to view them?</p>

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2017-06-27T17:40:34.237Z
This sounds half-way to [Olbers's Paradox](https://en.wikipedia.org/wiki/Olbers%27s_paradox)
Nick T
<star><universe><telescope><observational-astronomy><space>
Why when we look through a telescope in space, do the billions of stars not block our view from seeing further?
Cjolsen06
# Why when we look through a telescope in space, do the billions of stars not block our view from seeing further?

(Asked by: username_0 on 2016-02-14)

I know that we are able to "see back into time" by looking very far away through telescopes such as the Hubble telescope, but my question is, wouldn't you run into at least a couple of stars that were blocking your vision when you were trying to look even farther?

Imagine a big Boulder in front of another smaller Boulder and if we are looking from the side of the larger Boulder, we wouldn't be able to see the smaller one because the bigger one was in the way. Hopefully that simplifies my question. If it is as simple as that, wouldn't we miss stars and not be able to view them?

**Tags:** star, universe, telescope, observational-astronomy, space
> **Comments:**
> **username_1**: This sounds half-way to [Olbers's Paradox](https://en.wikipedia.org/wiki/Olbers%27s_paradox)  

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## 1 answers

### Answer by username_2 on 2016-02-14. Score: 11 | Accepted answer

OK, Imagine the stars at distance x block an area of the sky. At a distance of 2x there should be four times as many stars, but they would seem four times smaller in terms of area covered. Thus, the blocking grows linearly until a significant part of the sky is blocked. The stars within 20 light years (excluding the Sun), blocks approximately $4.3 \cdot 10^{-16}$ of the sky. Even if we scale that up to the radius of the universe, 45 billion light years, only about $2 \cdot 10^{-6}$ of the sky is covered.

Even that tiny number is an overestimate, as we live in an extremely star-dense part of the universe, our galaxy.

Space is simply too big.

> **Comments:**
> **username_3**: Great answer, but where do you have the $3\times10^{-19}$ from?  
> **username_2**: @pela It is calculated from the catalogue of stars within 21 light years http://www.johnstonsarchive.net/astro/nearstar.html , using an average radius. It may not be exact or representative in any way, and therefore deviate with at least one order of magnitude. But even then the conclusion holds.  
> **username_2**: @RobJeffries One can apparently not be careful enough with data. Manually checking the result of my table look-up, I found an error. The RMS stellar radius is 0.55 of the Sun and the representative distance 15 ly. The correct fraction is then $4.3 \cdot 10^{-16}$. Sorry about the previous error.  

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