Musings

https://www.space.com/33306-how-does-the-universe-expand-faster-than-light.html

Because stretchy stuff is stretchy, the objects on the fabric close to you would appear to move away with some speed, but the farther objects would appear to move faster. Even though the folks doing the pulling are moving at a constant speed, the apparent stretch changes with distance. I swear this is true; you can even try it for yourself at home!

The notion of the absolute speed limit comes from special relativity, but who ever said that special relativity should apply to things on the other side of the universe? That's the domain of a more general theory. A theory like…general relativity.

It's true that in special relativity, nothing can move faster than light. But special relativity is a local law of physics. Or in other words, it's a law of local physics. That means that you will never, ever watch a rocket ship blast by your face faster than the speed of light. Local motion, local laws. 

But a galaxy on the far side of the universe? That's the domain of general relativity, and general relativity says: who cares! That galaxy can have any speed it wants, as long as it stays way far away, and not up next to your face.

It goes deeper than this. Concepts like a well-defined "velocity" make sense only in local regions of space. You can only measure something's velocity and actually call it a "velocity" when it's nearby and when the rules of special relativity apply. Stuff super-duper far away, like the galaxies we're talking about it? If it's not close, it doesn't count as a “velocity” in the way that special relativity cares about.

Special relativity doesn't care about the speed — superluminal or otherwise — of a distant galaxy. And neither should you. 

***************

Space can curve and stretch
Space to infinity

First, it's important to know that the big bang wasn't an explosion of matter into empty space—it was the rapid expansion of space itself. This means that every single point in the universe appears to be at thecenter.

I know the balloon idea is a model.  After all, we cannot attempt to measure appearances that are presented to us except with models that are based on appearances.  As I understand it, the big bang explosion entailed a rapid expansion of space itself, so that every point in the universe would appear to be at the center.

Part of the big bang idea postulates a genesis that entails an expansion of space itself.  That space expanded.  So, was it only the space between proto-particles that expanded, while space itself has always been infinitely available in every direction?  Or did the big bang create new space as it moved into it?  Or is space-time folded back on itself, like a donut, with the donut continuously expanding, perhaps limited only by some exotic math?  I doubt science can avail reliable answers to such questions.

See http://www.iflscience.com/physics/will-universe-rip-itself-apart/.  Can a universe rip apart, if distances between galaxies were to become so great that not even light could ever again communicate between them?  If light could not radiate between them, then how long would the space-time that separates them continue to enforce gravitational effects between them?  If a big rip were to occur, could conservation of matter and energy still be rationalized?  Or would the total amount of matter and energy in each newly separate and ripped universe have diminished? 

Is there a postulated total value for all the matter and energy in the universe?  When every kind of energy is added, does the value net to zero, like a quantum fluctuation in a vacuum?  So, is the conservation to zero, or to infinity, or to a flux between zero and infinity?  Here is one stab at the issue:

"So the total potential energy of the universe is its unconsumed mass times the square of the speed of light in a vacuum, but active ephemeral energy flowing through space-time now is balanced by the gravity/mass that is absorbing it now.   Energy lost at one point of the universe is absorbed into space-time; and mass pulls it out of space-time into itself as gravity." --- https://www.quora.com/What-is-the-sum-of-total-energy-present-in-the-universe

Physically, we can play with a toy model for illustrating the expansion of space per the big bang, but our toy would be in space that had already been expressed, not in space that was being created or being expanded.  I doubt any physical toy could very well model any consensus of such ideas.

https://www.quora.com/If-the-universe-is-expanding-then-what-does-it-expand-into-What-do-we-call-that-space-which-accommodates-the-expanding-universe