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jbriggs444
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That is utterly wrong.Neandethal00 said:Saying a geometrical shape has no center is "practically incorrect".
That is utterly wrong.Neandethal00 said:Saying a geometrical shape has no center is "practically incorrect".
Neandethal00 said:The universe has no center.
OP was not asking for a center of a circle or center of a sphere.
Any spatial region must have a central 'region'. The region may
shift or constantly shift, but there must be region that we can call
central region of the universe.
Just because it is beyond the knowledge of 'current science', declaring
that universe has no center, in my opinion, is kind of escapism.
Neandethal00 said:A curvature can have many "centers of curvature" when it is divided into sections. Saying a geometrical shape has no center is "practically incorrect".
You agree that the 2d surface has no center on the surface, so therefore you must agree that the 3d universe has no center in its 3d space.Neandethal00 said:The center is located off the surface.
The relevant feature of the universe is that it is homogeneous and isotropic. That is, it is the same everywhere and in every direction. In order for there to be a center, there must be a violation of homogeneity. If such a violation is observed and verified then we would need to come up with an explanation. That explanation might or might not involve a center.Orien Rigney said:What happens if in the near future we find to our dismay, there is a center to the universe?
Orien Rigney said:What happens if in the near future we find to our dismay, there is a center to the universe?
Ryan Rankin said:I always like the balloon analogy.
Johninch said:I suppose that the questions about an imagined center of the universe arise from the assumption that the high original density had a source.
Johninch said:A source implies causality, so if time started with the BB, there was no cause and therefore no source.
Johninch said:Can somebody help me with the question: if we are saying that the original high density occurred everywhere, where does all this mass go when the density falls?
Johninch said:Is it assumed that dark energy has mass?
Johninch said:With the observed expansion of the universe, which we assume also to be the case in the non-observable universe, are we saying that there is an increasing emptiness (not containing dark energy or anything else) which is reducing mass per cubic light year?
Drakkith said:Dark energy is believed to remain at the same density while the density of normal and dark matter falls.
Johninch said:How can dark energy remain at the same density when the space between the (super) clusters is increasing?
Johninch said:Has emptiness been fully discredited (by Dirac) or does the universe contain emptiness?
Orien Rigney said:Uh-uh, it isn't going to work
No, it is not the least bit ridiculous, it is an analogy and analogies are by their very nature, flawed to one degree or another. The trick is to understand what part of the analogy is flawed and what part is helpful, but none of it is ridiculous. Similarly with the balloon analogy, as I explain in the link in my signature.Johninch said:It’s no use talking about raisin-bread. That’s ridiculous.
Because at non-cosmological levels, expansion is SO incredibly tiny that it cannot even begin to overcome the forces of gravity, let alone forces like the strong force. This is discussed some in the link in my signature.Enquerencia said:So expansion only exists in empty space, between galaxies and clusters? Why would this be?
Yes. If the universe is finite then having it become smaller does not help localize the center. It's still everywhere. If the universe is infinite then scaling it down does not help localize the center. It's still infinite. In any case, there is no "final time prior to the singularity" any more than there is a smallest real number greater than zero.Alexandra Fabiello said:I think a better question would be "If the universe stopped expanding and started shrinking instead, where in space would end up being in the middle of the final clump of matter before it went singularity on us?" Though that would probably still be 'everywhere', more or less, I suppose.
mathman said:In addition to expansion (significant only in large scale activity), galaxies have their own proper motion, so they can collide.
The universe has no center.
Even in a finite universe there is no size limit applicable (it sounds like you're saying size large enough it looks infinite). It's a geometry thing: the surface of the Earth has no center. The universe is like a 3D surface, curved in a higher dimension. It's hard to visualize, but just like flying around the world, you may be able to fly across the universe and end up where you started.Flo Tur said:The solar sistem has a center of mass. Similar, a galaxy, a cluster of galaxies, etc, have a center of mass. What is the limit from where we cannot speak anymore about a center of a mass, in a finite Universe?
The standard flat ΛCDM model is the easiest example.Flo Tur said:Do you have a mathematical representation of a universe finit in time but infinite in volume?