The discussion centers on the misconception that the universe has a center, with participants clarifying that the universe is expanding uniformly without a singular point of origin. The term "singularity" is defined as a breakdown of mathematical models rather than a specific location in space. Participants emphasize that while galaxies are moving away from each other due to cosmic expansion, they can still collide due to their own proper motion. The observable universe is limited by the speed of light and the age of the universe, making the concept of a central point irrelevant.
PREREQUISITESAstronomers, astrophysicists, students of cosmology, and anyone interested in understanding the structure and dynamics of the universe.
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?