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

  • 6
    $\begingroup$ 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. $\endgroup$
    – pela
    Commented Jun 17, 2022 at 19:12
  • 2
    $\begingroup$ @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. $\endgroup$
    – Felicia
    Commented Jun 18, 2022 at 5:04
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    $\begingroup$ Yes, that’s right. That would violate the cosmological principle, though. $\endgroup$
    – pela
    Commented Jun 18, 2022 at 6:45


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