<p>Things that are bound by other forces will not be seperated by the expansion of the Universe. For instance, planets do not expand due to cosmic expansion. The solar system does not either because it is held together by gravity. However, the space between galaxies or between galaxy clusters does expand. </p>

CC BY-SA 4.0
2020-01-30T08:32:14.150Z
2020-01-30T08:32:14.150Z
usernumber
<p>Think of the universe as a partially inflated balloon. If you decrease the air pressure of the air outside of the balloon then the balloon inflates. The density of the air in the balloon has just dropped because the mass is the same but it is taking up more space. The air molecules have spread farther away from each other but the molecules themselves don't expand. This is the same thing that happens to everything in our universe as it expands. The space between the components of particles has increased.</p>

CC BY-SA 4.0
2020-01-30T06:06:30.607Z
So yes or no, ..."do things like planets expand also?" [balloon and raisin cake analogies](https://physics.stackexchange.com/q/251700/83380) usually avoid answering this directly. A planet drawn on a balloon would expand, a raisin in a cake won't.
uhoh
CC BY-SA 4.0
2020-01-31T04:21:41.270Z
So it will start off at the subatomic level, atom's components will spread apart, then as the expansion of the universe speeds up eventually, theoretically, planets will, more explode once you reach this stage, expand.
Daosof
CC BY-SA 4.0
2020-01-30T04:06:48.340Z
2020-01-30T09:05:25.827Z
2020-01-30T09:05:25.827Z
Daosof
<p>Just what the question says. As the universe expands, and space expands, do objects like planets ever expand? Does the space INSIDE of those objects expand?   </p>

CC BY-SA 4.0
2019-03-21T17:30:21.067Z
Things that are bound by some force (planets bound by gravity, etc) stay the same. Things that are unbound will drift apart.
Florin Andrei
CC BY-SA 4.0
2019-03-21T17:40:44.037Z
Nice question, probably it was asked already many times :-) The important thing is: *we can't measure anything absolutely. All measurement compares something to another thing. Thus, if everything would expand, we couldn't measure it. How? All of our measuring devices would also expand.*
peterh
CC BY-SA 4.0
2019-03-21T18:45:44.213Z
Closely related: https://astronomy.stackexchange.com/questions/11726/does-the-universe-expand-at-the-same-rate-everywhere-in-the-universe
PM 2Ring
CC BY-SA 4.0
2019-03-22T11:30:35.633Z
See also: https://astronomy.stackexchange.com/questions/104/on-what-scale-does-the-universe-expand
mtewes
CC BY-SA 4.0
2019-03-22T17:49:41.143Z
I think it's the latter, Keith.
John Duffield
CC BY-SA 4.0
2019-03-24T12:02:49.533Z
@prterh the force between two charges would be seen decreasing, just to mention one thing that leads us to conclude that at least something is changing
Alchimista
<universe><space>
As the Universe expands, do things like planets expand also, or just the space in between?
Keith
# As the Universe expands, do things like planets expand also, or just the space in between?

(Asked by: username_0 on 2019-03-21)

Just what the question says. As the universe expands, and space expands, do objects like planets ever expand? Does the space INSIDE of those objects expand?

**Tags:** universe, space

> **Comments:**
> **username_1**: Things that are bound by some force (planets bound by gravity, etc) stay the same. Things that are unbound will drift apart.  
> **username_2**: Nice question, probably it was asked already many times :-) The important thing is: *we can't measure anything absolutely. All measurement compares something to another thing. Thus, if everything would expand, we couldn't measure it. How? All of our measuring devices would also expand.*  
> **username_3**: Closely related: https://astronomy.stackexchange.com/questions/11726/does-the-universe-expand-at-the-same-rate-everywhere-in-the-universe  
> **username_4**: See also: https://astronomy.stackexchange.com/questions/104/on-what-scale-does-the-universe-expand  
> **username_5**: I think it's the latter, username_0.  
> **username_6**: @prterh the force between two charges would be seen decreasing, just to mention one thing that leads us to conclude that at least something is changing  

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## 2 answers

### Answer by username_7 on 2020-01-30. Score: 3

Things that are bound by other forces will not be seperated by the expansion of the Universe. For instance, planets do not expand due to cosmic expansion. The solar system does not either because it is held together by gravity. However, the space between galaxies or between galaxy clusters does expand.


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### Answer by username_8 on 2020-01-30. Score: -1

Think of the universe as a partially inflated balloon. If you decrease the air pressure of the air outside of the balloon then the balloon inflates. The density of the air in the balloon has just dropped because the mass is the same but it is taking up more space. The air molecules have spread farther away from each other but the molecules themselves don't expand. This is the same thing that happens to everything in our universe as it expands. The space between the components of particles has increased.

> **Comments:**
> **username_9**: So yes or no, ..."do things like planets expand also?" [balloon and raisin cake analogies](https://physics.stackexchange.com/q/251700/83380) usually avoid answering this directly. A planet drawn on a balloon would expand, a raisin in a cake won't.  
> **username_8**: So it will start off at the subatomic level, atom's components will spread apart, then as the expansion of the universe speeds up eventually, theoretically, planets will, more explode once you reach this stage, expand.  

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