<p>Actually not everything is moving apart. On a scale of millions of light years  gravity dominates and there isn't metric expansion of space.  This is why (for example) the Andromeda galaxy is moving towards the Milky Way.</p>
<p>So nearby stars (only a few tens of light years away) are not affected by the expansion of spacetime at all.</p>
<p>In the very distant future (countless trillions of years, ie long after the sun has died) it is possible that the expansion of space accelerates to the point that objects on smaller and smaller scales move apart. This is sometimes called the <a href="https://en.wikipedia.org/wiki/Big_Rip" rel="nofollow noreferrer">Big Rip</a>.  It is strictly hypothetical, and observations tend to suggest it won't happen at all.</p>
<p>So the short answer is &quot;no&quot;, stars won't get dimmer due to the expansion of space, because in locally, it's not expanding.</p>

CC BY-SA 4.0
2022-10-02T18:41:15.153Z
Why is it not expanding seen locally? Is there something about solving the Einstein field equations that gives expansion basically between galaxies but not locally?
Agerhell
CC BY-SA 4.0
2022-10-02T18:53:36.627Z
There is too much mass locally for it to expand.   ProfRob could give chapter and verse.  The expansion (as described in the Friedmann equations) assumes a  homogeneous universe - which is true on average over large volumes, but not true locally.
James K
CC BY-SA 4.0
2022-10-05T22:15:21.817Z
@Agerhell GR with a cosmological constant behaves somewhat like a modified Newtonian gravity with a second term in the acceleration: $a=GM/r^2-\frac13 Λr$. If you equate that to $ω^2 r$ you get $ω=\sqrt{GM/r^3 - Λ/3}$. If $r$ is large enough, the quantity in the square root is negative and no circular orbit is possible. At smaller $r$, the second term just slightly changes the $ω$-$r$ relationship.
benrg
CC BY-SA 4.0
2022-10-02T18:34:56.973Z
2022-10-02T18:34:56.973Z
James K
<p>We know that the universe is expanding, and that means everything is spreading apart. So does that mean in the future all the stars will dim and eventually disappear in our night sky because of the expansion? Just a curious thought that came to mind.</p>

CC BY-SA 4.0
2022-10-02T18:33:05.537Z
According to expansion theory there is not really any expansion going on within galaxies such as our Milky Way. So even if other galaxies drift further away from us you would still be able to see all the stars in our galaxy.
Agerhell
<universe><night-sky><future>
Will the stars dim in the future because of the expansion of the universe?
Prince Pugs
# Will the stars dim in the future because of the expansion of the universe?

(Asked by: username_0 on 2022-10-02)

We know that the universe is expanding, and that means everything is spreading apart. So does that mean in the future all the stars will dim and eventually disappear in our night sky because of the expansion? Just a curious thought that came to mind.

**Tags:** universe, night-sky, future

> **Comments:**
> **username_1**: According to expansion theory there is not really any expansion going on within galaxies such as our Milky Way. So even if other galaxies drift further away from us you would still be able to see all the stars in our galaxy.  

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## 1 answers

### Answer by username_2 on 2022-10-02. Score: 3 | Accepted answer

Actually not everything is moving apart. On a scale of millions of light years gravity dominates and there isn't metric expansion of space. This is why (for example) the Andromeda galaxy is moving towards the Milky Way.

So nearby stars (only a few tens of light years away) are not affected by the expansion of spacetime at all.

In the very distant future (countless trillions of years, ie long after the sun has died) it is possible that the expansion of space accelerates to the point that objects on smaller and smaller scales move apart. This is sometimes called the [Big Rip](https://en.wikipedia.org/wiki/Big_Rip). It is strictly hypothetical, and observations tend to suggest it won't happen at all.

So the short answer is "no", stars won't get dimmer due to the expansion of space, because in locally, it's not expanding.

> **Comments:**
> **username_1**: Why is it not expanding seen locally? Is there something about solving the Einstein field equations that gives expansion basically between galaxies but not locally?  
> **username_2**: There is too much mass locally for it to expand.   ProfRob could give chapter and verse.  The expansion (as described in the Friedmann equations) assumes a  homogeneous universe - which is true on average over large volumes, but not true locally.  
> **username_3**: @username_1 GR with a cosmological constant behaves somewhat like a modified Newtonian gravity with a second term in the acceleration: $a=GM/r^2-\frac13 Λr$. If you equate that to $ω^2 r$ you get $ω=\sqrt{GM/r^3 - Λ/3}$. If $r$ is large enough, the quantity in the square root is negative and no circular orbit is possible. At smaller $r$, the second term just slightly changes the $ω$-$r$ relationship.  

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