The universe possesses a globally defined fixed center of mass
the verdict
REFUTED
the evidence says no
refutedsupported
the weight of evidence
0 sources for · 2 against
AS REPORTEDno primary record reached; this is what the reporting says
Cosmological consensus and expert physics explanations report that the universe possesses neither a center nor a globally defined fixed center of mass.
# Does the universe have a fixed centre of mass?
Tags: cosmology, spacetime, mass, universe
- Score: 25
- Views: 5619
- Answers: 5
- Answered: yes
- Asked by: Tapi (465 rep)
- Asked: 2019-04-21
- Edited: 2019-04-21
- Site: physics
## Question
Does the universe have a fixed centre of mass?
If it does, doesn't it necessarily mean that every action of ours has to be balanced by a counteraction somewhere in the universe so as to neutralize the disbalance of mass?
## Answers
### Answer by John Rennie (score: 30 [ACCEPTED])
As far as we know, the universe does not have a centre of mass because it does not have a centre. One of the basic assumptions we use when describing the universe is that, on average, it is the same everywhere. This is called the cosmological principle. While this is only an assumption, the evidence we have from observing the universe suggests that it is true.
This can seem a bit odd if you have the idea that the Big Bang happened at a point and the Big Bang blasted the universe outwards from that point. But the Big Bang did not happen at a point; it happened everywhere in the universe at the same time. For more on this, see Did the Big Bang happen at a point?
# Is there any net external force acting on the universe?
Tags: newtonian-mechanics, forces, cosmology, inertial-frames, universe
- Score: 0
- Views: 593
- Answers: 1
- Answered: yes
- Asked by: kiss my armpit (1082 rep)
- Asked: 2015-01-03
- Edited: 2022-06-05
- Site: physics
## Question
If we consider the universe as a system, is there any net external force acting on it? I am thinking of whether or not the center of mass of the system moves. If there is no such a net external force then the center of mass of our universe must not move. Is it correct?
As a result, this center of mass can then be used as an absolute inertial frame of reference.
## Answers
### Answer by ACuriousMind (score: 12)
The universe has no center. It also doesn't have a center of mass.
The notion of "a force exerted on the universe" would need the universe to be able to move somewhere, since that's what forces (classically) do - they move things. But the universe is all there is, including spacetime, and the notion of "spacetime moving somewhere" is ill-defined.
Rather tautologically, the universe is "all that there is" - if the were a notion of force on it, there would be a notion of something
Everything we examined (2) — 1 independent source
This check searched the claim as stated. It did not run a separate search for evidence against it.