<p>It's going to be all (or perhaps <em>nearly</em> all) of the observable Universe. Roughly speaking, there are <a href="http://science.howstuffworks.com/milky-way5.htm">several hundred billion stars</a> in the Milky Way. And extrapolating the number of galaxies in deep Hubble images suggests <a href="http://www.space.com/25303-how-many-galaxies-are-in-the-universe.html">something like</a> a hundred billion galaxies in the observable Universe.  Put these together and <a href="http://www.esa.int/Our_Activities/Space_Science/Herschel/How_many_stars_are_there_in_the_Universe">you get about</a> $10^{22}$ to $10^{24}$ stars in the observable Universe.  Avogadro's number is $6.022\times 10^{23}$, which is in the upper end of that range.  So, given current estimates, you'd need at least most, if not all, of the observable Universe to get $N_A$ stars.</p>

CC BY-SA 3.0
2014-09-10T18:33:55.700Z
2014-09-12T01:02:35.963Z
2014-09-12T01:02:35.963Z
Warrick
<p>I think that the answer to this question will be useful as a scale to appreciate the size of the universe.</p>

<p>So, <strong>If we count Avogadro's Number of stars that are closest to Earth, how big that space would be?</strong> And how many galaxies/clusters will be engulfed in that space? And for a start, let's just consider only three dimensions.</p>

CC BY-SA 3.0
2014-09-11T00:24:34.760Z
What do you mean by "only three dimensions"?
HDE 226868
CC BY-SA 3.0
2014-09-11T01:01:45.980Z
@HDE226868: If one considers time as the 4th dimension, there may be closer stars to Earth in the past and future.
sampathsris
CC BY-SA 3.0
2014-09-11T01:02:50.247Z
But do we consider that dimension when talking about, say, the size of a galaxy?
HDE 226868
CC BY-SA 3.0
2014-09-11T01:04:22.740Z
@HDE226868 Of course not. It was there so that the question may not become too broad, for people who are interested about too much detail, like me.
sampathsris
CC BY-SA 3.0
2014-10-21T02:51:03.273Z
By the way, I started following Scientific Imagination a while ago!
HDE 226868
<star><distances>
If we count Avogadro's Number of stars that are closest to Earth, how big that space would be?
sampathsris
# If we count Avogadro's Number of stars that are closest to Earth, how big that space would be?

(Asked by: username_0 on 2014-09-10)

I think that the answer to this question will be useful as a scale to appreciate the size of the universe.

So, **If we count Avogadro's Number of stars that are closest to Earth, how big that space would be?** And how many galaxies/clusters will be engulfed in that space? And for a start, let's just consider only three dimensions.

**Tags:** star, distances

> **Comments:**
> **username_1**: What do you mean by "only three dimensions"?  
> **username_0**: @username_1: If one considers time as the 4th dimension, there may be closer stars to Earth in the past and future.  
> **username_1**: But do we consider that dimension when talking about, say, the size of a galaxy?  
> **username_0**: @username_1 Of course not. It was there so that the question may not become too broad, for people who are interested about too much detail, like me.  
> **username_1**: By the way, I started following Scientific Imagination a while ago!  

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## 1 answers

### Answer by username_2 on 2014-09-10. Score: 22 | Accepted answer

It's going to be all (or perhaps *nearly* all) of the observable Universe. Roughly speaking, there are [several hundred billion stars](http://science.howstuffworks.com/milky-way5.htm) in the Milky Way. And extrapolating the number of galaxies in deep Hubble images suggests [something like](http://www.space.com/25303-how-many-galaxies-are-in-the-universe.html) a hundred billion galaxies in the observable Universe. Put these together and [you get about](http://www.esa.int/Our_Activities/Space_Science/Herschel/How_many_stars_are_there_in_the_Universe) $10^{22}$ to $10^{24}$ stars in the observable Universe. Avogadro's number is $6.022\times 10^{23}$, which is in the upper end of that range. So, given current estimates, you'd need at least most, if not all, of the observable Universe to get $N\_A$ stars.


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