<p>They do move - just far too slowly for you to detect by eye even over several human lifetimes.</p>

<blockquote>
  <p>Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space</p>
</blockquote>

<p><em>Douglas Adams, "The Hitch-hikers Guide to the Galaxy"</em></p>

<p>Even the closest stars are a very, very, very long way away so their apparent movement relative to each other is going to be very small.</p>

<p>You can see the same effect when looking out of a moving vehicle through the side windows. You see the objects closest to you rushing past, but objects on the horizon appear to move much more slowly. Now, scale that up by many orders of magnitude to interstellar distances and you'll see why the stars don't appear to move relative to each other.</p>

<p>There's software that simulates the night sky and you can run time backwards and forwards - if you wind it far enough you'll see the constellations change.</p>

CC BY-SA 3.0
2016-01-14T09:36:59.063Z
2016-01-14T14:10:41.763Z
2016-01-14T14:10:41.763Z
ChrisF
<p>Here's a nice image of <a href="https://en.wikipedia.org/wiki/Barnard&#39;s_Star" rel="nofollow noreferrer">Barnard's star</a> moving against the stellar background:
<a href="https://i.sstatic.net/z0ge0.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/z0ge0.jpg" alt="enter image description here"></a>
From this interesting website: <a href="http://sites.psu.edu/astrowright/2012/08/14/barnards-stars-planets/" rel="nofollow noreferrer">AstroWright</a></p>

CC BY-SA 3.0
2016-01-14T19:22:27.847Z
2016-01-14T19:22:27.847Z
Wayfaring Stranger
<p>Obviously Space is big… however so too is time. After-all we still aren’t to sure how to distinguish time from space and space from time. Still, over the thousands of years our ancestors have been star gazing these many stars it is logical to believe that, if they move, and if they move independently, then the many “constellations” would appear different today. Orion would look either more skinny at the waist, bigger at the waist, or more leaned forward or backward, or his waist indiscernible completely. And that’s speaking of just one - Orion - and only one facet of that constellation too.</p>
<p>Take the Big Dipper now. Surely IF the stars move independently and from very far away and are moving quicker than us, then relative to us they would move quicker than we’d appear to, to them (parallax), and so the Big Dipper (like Orion) would look different today than it did thousands of years ago. The Big Dipper should be flatter or longer or shorter or indiscernible because all it’s stars went in all different directions and in different amounts too. But no!</p>
<p>Just like Orion, and indeed all the constellations, the Big Dipper remains the same. Even adding the time delay of the light emissions, by now the stars should appear differently to us than they did to our very old ancestors.</p>
<p>The main argument I’ve seen is “parallax”: arguing that LIKE on a drive in the car, passing telephone poles vs passing mountains further in the distance, the poles move quicker than the mountains due to “parallax”. That both objects are moving at the same rate but the distance is what causes the illusion of the further object moving slower. However, one glaring issue/problem with that argument is the fact that we the observer are PREMISED to be the ones moving whereas the poles and mountains are premised as stationary… but the argument concludes absurdly that both the stationary objects are moving… so it’s unsound. For that reason I disagree with the parallax argument.</p>
<p>Yet, if we correct our premises, still we have a problem. That is, the stars are moving much quicker than Earth, unless you think they’re stationary (roughly speaking). So, if parallax can be used, then we should be like the ‘mountain’ and the distant star be like ‘the car’. Thus, according to correct parallax, relative to us (the mountain) the distant star (the car) should be moving very quickly in whatever direction it’s vector is. Alas, the constellations appear fixed, and so that apparent movement is not there and so even correct parallax doesn’t work.</p>
<p>The question remains, if the stars are not stationary, why do they appear to be after thousands of years??</p>

CC BY-SA 4.0
2022-11-15T18:34:37.520Z
Because the relative motion at tens of km/s means that they hardly move on the sky even over thousands of years because they are so far away. You can't argue against this with intuition and "common sense" arguments. The stars are clearly further way than you can imagine.
ProfRob
CC BY-SA 4.0
2022-11-15T19:16:05.117Z
This question already has perfectly valid answers, please study them first, before posting a wall of text, years later. The short answer is 'the enormous distances of space'.
AtmosphericPrisonEscape
CC BY-SA 4.0
2022-11-16T02:00:46.377Z
-1. "the Big Dipper remains the same", except it does not remain the same. The Big Dipper and Orion DO change shape. The problem is the change is very small, and it is caused by Proper Motion of the stars, not Parallax due to the Earth's orbit around the Sun. Proper motion was confirmed by Halley in 1718 using observations from Hipparchus approximately 1800 years earlier.
JohnHoltz
CC BY-SA 4.0
2022-11-18T17:46:34.407Z
As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Community
CC BY-SA 4.0
2022-11-15T18:05:46.773Z
2022-11-15T18:06:11.567Z
2022-11-15T18:06:11.567Z
JackStar
<p>Whilst I understand why stars move across our skies,(Earth rotation) I struggle to understand why they do not appear to move relative to each other.</p>

<p>To explain:  Take the best know constellation the Plough.  It is a familiar site to most people.  But it has been there apparently un-changed for years.  If we (I mean earth, moon, stars and everything else ) are hurtling through space, then surely changes should be apparent unless we are all travelling in the same direction at exactly the same speed.</p>

CC BY-SA 3.0
2016-01-14T12:26:56.067Z
You picked a bad example! Most of the stars in the Plough are in fact part of the co-moving UMa group and so are moving in the same direction at the same speed! But the answer is basically that they do, just at a rate which is imperceptible to the human eye (but quite measurable with telescopes).
ProfRob
<positional-astronomy>
Why do stars seem not to move relative to each other?
Barrie
# Why do stars seem not to move relative to each other?

(Asked by: username_0 on 2016-01-14)

Whilst I understand why stars move across our skies,(Earth rotation) I struggle to understand why they do not appear to move relative to each other.

To explain: Take the best know constellation the Plough. It is a familiar site to most people. But it has been there apparently un-changed for years. If we (I mean earth, moon, stars and everything else ) are hurtling through space, then surely changes should be apparent unless we are all travelling in the same direction at exactly the same speed.

**Tags:** positional-astronomy

> **Comments:**
> **username_1**: You picked a bad example! Most of the stars in the Plough are in fact part of the co-moving UMa group and so are moving in the same direction at the same speed! But the answer is basically that they do, just at a rate which is imperceptible to the human eye (but quite measurable with telescopes).  

---

## 3 answers

### Answer by username_2 on 2016-01-14. Score: 5

They do move - just far too slowly for you to detect by eye even over several human lifetimes.

> Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space

*Douglas Adams, "The Hitch-hikers Guide to the Galaxy"*

Even the closest stars are a very, very, very long way away so their apparent movement relative to each other is going to be very small.

You can see the same effect when looking out of a moving vehicle through the side windows. You see the objects closest to you rushing past, but objects on the horizon appear to move much more slowly. Now, scale that up by many orders of magnitude to interstellar distances and you'll see why the stars don't appear to move relative to each other.

There's software that simulates the night sky and you can run time backwards and forwards - if you wind it far enough you'll see the constellations change.


---

### Answer by username_3 on 2016-01-14. Score: 4

Here's a nice image of [Barnard's star](https://en.wikipedia.org/wiki/Barnard's_Star) moving against the stellar background:
[![enter image description here](https://i.sstatic.net/z0ge0.jpg)](https://i.sstatic.net/z0ge0.jpg)
From this interesting website: [AstroWright](http://sites.psu.edu/astrowright/2012/08/14/barnards-stars-planets/)


---

### Answer by username_4 on 2022-11-15. Score: -6

Obviously Space is big… however so too is time. After-all we still aren’t to sure how to distinguish time from space and space from time. Still, over the thousands of years our ancestors have been star gazing these many stars it is logical to believe that, if they move, and if they move independently, then the many “constellations” would appear different today. Orion would look either more skinny at the waist, bigger at the waist, or more leaned forward or backward, or his waist indiscernible completely. And that’s speaking of just one - Orion - and only one facet of that constellation too.

Take the Big Dipper now. Surely IF the stars move independently and from very far away and are moving quicker than us, then relative to us they would move quicker than we’d appear to, to them (parallax), and so the Big Dipper (like Orion) would look different today than it did thousands of years ago. The Big Dipper should be flatter or longer or shorter or indiscernible because all it’s stars went in all different directions and in different amounts too. But no!

Just like Orion, and indeed all the constellations, the Big Dipper remains the same. Even adding the time delay of the light emissions, by now the stars should appear differently to us than they did to our very old ancestors.

The main argument I’ve seen is “parallax”: arguing that LIKE on a drive in the car, passing telephone poles vs passing mountains further in the distance, the poles move quicker than the mountains due to “parallax”. That both objects are moving at the same rate but the distance is what causes the illusion of the further object moving slower. However, one glaring issue/problem with that argument is the fact that we the observer are PREMISED to be the ones moving whereas the poles and mountains are premised as stationary… but the argument concludes absurdly that both the stationary objects are moving… so it’s unsound. For that reason I disagree with the parallax argument.

Yet, if we correct our premises, still we have a problem. That is, the stars are moving much quicker than Earth, unless you think they’re stationary (roughly speaking). So, if parallax can be used, then we should be like the ‘mountain’ and the distant star be like ‘the car’. Thus, according to correct parallax, relative to us (the mountain) the distant star (the car) should be moving very quickly in whatever direction it’s vector is. Alas, the constellations appear fixed, and so that apparent movement is not there and so even correct parallax doesn’t work.

The question remains, if the stars are not stationary, why do they appear to be after thousands of years??

> **Comments:**
> **username_1**: Because the relative motion at tens of km/s means that they hardly move on the sky even over thousands of years because they are so far away. You can't argue against this with intuition and "common sense" arguments. The stars are clearly further way than you can imagine.  
> **username_5**: This question already has perfectly valid answers, please study them first, before posting a wall of text, years later. The short answer is 'the enormous distances of space'.  
> **username_6**: -1. "the Big Dipper remains the same", except it does not remain the same. The Big Dipper and Orion DO change shape. The problem is the change is very small, and it is caused by Proper Motion of the stars, not Parallax due to the Earth's orbit around the Sun. Proper motion was confirmed by Halley in 1718 using observations from Hipparchus approximately 1800 years earlier.  
> **username_7**: As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer).  

---

