<p>For your experiment, you can take it 2D, so let's ingnore the thickness of Milky Way.</p>

<p>So, we have 400 billions stars(the real number is between 100B-400B) in a circle with 100k ly(the real number is between 100k-160k). </p>

<p>The area of the circle is pi*50k*50k ~= 7800M sqly = 7.8 billions sqly.</p>

<p>We have then ~51 randomly stars per square ly.</p>

<p>But you do not sting the Milky Way with your stick, but cut through it.</p>

<p>If you swipe through the middle, you have 51*100k stars in a width of 1 ly.</p>

<p>So, you have a chance to hit a star per 1/5.100.000 ly which means 1.855.000km. </p>

<p>But the diameter of sun(of your stick) is 1.395.000km. Taking diameter of sun as medium diameter of a star(this is not true), you have a chance of 1.4/1.8 = 77% to hit a star. If you go with the "low density" numbers, 100B stars and 160k ly diameter, you'll get ~31%.</p>

<p>My conclusion is you often hit a star.</p>

CC BY-SA 3.0
2016-02-17T14:23:03.593Z
I concur. Nice calculation.
ProfRob
CC BY-SA 3.0
2016-02-17T11:11:01.517Z
2016-02-17T11:11:01.517Z
Florin Ghita
<p>If I had a long stick that was millions of light years long, and with a width of about the Sun, and I then swiped it through the center of the milky way galaxy, what would the probability be of me hitting a star?</p>

<p>EDIT:</p>

<ul>
<li>Ignore the speed of light. Assume it is possible to just swipe it through instantaneiously.</li>
<li>Assume that the stars in the galaxy are equally distributed. Obviously if you were to swipe right through the middle you would hit the galactic center.</li>
<li>The purpose of this thought experiment is just to help visualise the density vs size of the galaxy.</li>
</ul>

CC BY-SA 3.0
2016-02-17T08:53:18.683Z
my own gut feeling would be about 1%!!!
Oliver Watkins
<galaxy><milky-way>
visualisation of galaxy density
Oliver Watkins
# visualisation of galaxy density

(Asked by: username_0 on 2016-02-16)

If I had a long stick that was millions of light years long, and with a width of about the Sun, and I then swiped it through the center of the milky way galaxy, what would the probability be of me hitting a star?

EDIT:

* Ignore the speed of light. Assume it is possible to just swipe it through instantaneiously.
* Assume that the stars in the galaxy are equally distributed. Obviously if you were to swipe right through the middle you would hit the galactic center.
* The purpose of this thought experiment is just to help visualise the density vs size of the galaxy.

**Tags:** galaxy, milky-way
> **Comments:**
> **username_0**: my own gut feeling would be about 1%!!!  

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## 1 answers

### Answer by username_1 on 2016-02-17. Score: 4

For your experiment, you can take it 2D, so let's ingnore the thickness of Milky Way.

So, we have 400 billions stars(the real number is between 100B-400B) in a circle with 100k ly(the real number is between 100k-160k).

The area of the circle is pi\*50k\*50k ~= 7800M sqly = 7.8 billions sqly.

We have then ~51 randomly stars per square ly.

But you do not sting the Milky Way with your stick, but cut through it.

If you swipe through the middle, you have 51\*100k stars in a width of 1 ly.

So, you have a chance to hit a star per 1/5.100.000 ly which means 1.855.000km.

But the diameter of sun(of your stick) is 1.395.000km. Taking diameter of sun as medium diameter of a star(this is not true), you have a chance of 1.4/1.8 = 77% to hit a star. If you go with the "low density" numbers, 100B stars and 160k ly diameter, you'll get ~31%.

My conclusion is you often hit a star.

> **Comments:**
> **username_2**: I concur. Nice calculation.  

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