Question regarding movement of universe

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Discussion Overview

The discussion revolves around the movement and expansion of the universe, specifically questioning the concept of a center of mass within the universe and its implications for the motion of the Solar System. Participants explore theoretical aspects of cosmology, including gravitational forces and the nature of the universe's expansion.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether the universe has a center of mass and suggests that the expansion of the universe implies a changing center of mass, which may relate to the motion of the Solar System.
  • Another participant challenges the assumption of a center of mass, using the balloon analogy to illustrate that the universe may not have a defined center.
  • There is confusion expressed regarding the concept of gravitational force within the universe and whether it can be said to "move." A participant speculates that if the universe moves, it could imply the existence of an object with greater mass than the universe itself.
  • A later reply reiterates the balloon analogy, emphasizing that while the universe expands, it does not make sense to discuss the motion of a center of mass.
  • Another participant notes that the universe is expanding but argues that this does not necessarily indicate movement of a center of mass, highlighting the complexity of defining such a center based on different cosmological models.
  • Concerns are raised about the observable universe and the implications of unobservable regions on the concept of a center of mass.

Areas of Agreement / Disagreement

Participants express differing views on the existence and implications of a center of mass in the universe. There is no consensus on whether the universe has a center of mass or how its expansion relates to the motion of the Solar System.

Contextual Notes

Participants acknowledge limitations in understanding due to the vastness of the universe and the challenges of observing most of it. The discussion also touches on the implications of the cosmological constant and dark matter, which remain unresolved.

FeDeX_LaTeX
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I'm no physicist, but I just have some questions...

1) The universe is expanding, correct? This means that its centre of mass is constantly changing, and the centre of the universe is also constantly changing (well... if the universe is spherical, and was increasing in proportion to a sphere). Is this why our Solar System is moving?

(going to post the other questions about neutronium in other thread, since I was given a warning for asking more than 1 question in a thread)
 
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You assume that there is a center of mass. That is open to question. Using the well known balloon analogy, where is the center of the SURFACE of a balloon?
 
The surface of the universe? I don't know... that is confusing. Does the universe have a gravitational force? And does it move?

I was just thinking that, if it *did* move, then that would imply that there would be an object having a greater mass than the universe due to gravitational force.

...Wait, how can something not have a centre of mass?
 
Last edited:
FeDeX_LaTeX said:
The surface of the universe? I don't know... that is confusing. Does the universe have a gravitational force? And does it move?

I was just thinking that, if it *did* move, then that would imply that there would be an object having a greater mass than the universe due to gravitational force.

...Wait, how can something not have a centre of mass?

Think of the balloon analogy for a 2d universe. The universe is on the surface of the balloon, which is expanding. Points on the balloon move away from each other as it expands. Even though the universe is expanding, it doesn't make sense to talk about motion of a centre of mass.

Torquil
 
1) The universe is expanding, correct? This means that its centre of mass is constantly changing, and the centre of the universe is also constantly changing (well... if the universe is spherical, and was increasing in proportion to a sphere). Is this why our Solar System is moving?

The universe IS expanding but that says nothing about possible movement of it's "center of mass". Every distance point moves away from evry other distant point; nearby points are usually held firm by gravitational attraction.

A "center of mass" for the universe depends on what model of the universe you are considering...a practical problem is that 99.9999...% of the universe is probably not observable..meaning we have no causal contact, no means to detect it.

Each increment of space not bound by gravitational attraction apparently gives rise to new space...due to the cosmological constant, maybe dark matter. That new space is "empty" and has only zero average energy, quantum fluctuations, and so has no inherent mass nor energy nor I would guess pressure...all gravitational components in general relativity. That means insofar as we know that the total mass and energy in the universe is constant...conservation of mass energy...

This question should be moved to the cosmology forum...evolution of the universe..
 

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