<p>If we envision the universe like a balloon but in 3D, is it possible, in general, to assign a of global center of mass?</p>

CC BY-SA 4.0
2022-06-17T19:12:15.633Z
No, just like the closed 2D surface of a balloon doesn't have any center, so doesn't the 3D volume of a closed Universe.
pela
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2022-06-18T05:04:53.490Z
@pela Doesn't it depend on the mass distribution? If there are two masses on opposite sides of the balloon, there will be a ring  of CoM. For a one-sided distribution, it will lay on one side. For just one mass, it will be somewhere in that mass.
Felicia
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2022-06-18T06:45:54.933Z
Yes, that’s right. That would violate the cosmological principle, though.
pela
<cosmology><space><mass>
If the universe is a closed spacetime structure, can we assign a center of mass to it?
Felicia
# If the universe is a closed spacetime structure, can we assign a center of mass to it?

(Asked by: username_0 on 2022-06-17)

If we envision the universe like a balloon but in 3D, is it possible, in general, to assign a of global center of mass?

**Tags:** cosmology, space, mass

> **Comments:**
> **username_1**: No, just like the closed 2D surface of a balloon doesn't have any center, so doesn't the 3D volume of a closed Universe.  
> **username_0**: @username_1 Doesn't it depend on the mass distribution? If there are two masses on opposite sides of the balloon, there will be a ring  of CoM. For a one-sided distribution, it will lay on one side. For just one mass, it will be somewhere in that mass.  
> **username_1**: Yes, that’s right. That would violate the cosmological principle, though.  

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## 0 answers

