the universe was 10^-35 meters a fraction of a second after the big bang, but isn't that a relative size? Relative to our current space/time reference frame? Time ran slower back then but if you were there you wouldn't know it, isn't it the same for space as well? isn't space static but we see it through a changing lorentz factor?
1916 Albert Einstein ''discovered'' space-time and this was widely accepted . As a consequence of this in 1927
Georges Henri Joseph Édouard Lemaître wrote the Big Bang Theory based on available information and concensus . The Big Bang Theory was then accepted by the scientific community and the Church as being the beginning . This allowed science to have their say but also kept God ''in the frame'', George being a Catholic Priest and a part of Vatican Astronomy Science .
I am struggling to find on the internet an original read of Georges work but I do not believe that he meant before the Big Bang there was nothing , this including space. I beleive he meant there was no things , such as matter .
What this implies is that before the Big Big there was pre-existing space and as Newton explained prior , an immovable space . This implication would then satisfy physical application because in Physics , any thing that expands requires pre-existing space to expand into .
So in answer to your question , the underlying space is immovable !
A hint : Try to avoid the use of the word
''static'' when discussing immovable because
''static'' is relative to Electrical charge .
The Space-Time metric expansion is relative to space . Space-time is dynamic in measure ,where space is a constant measure !
(x0,x1,x2,..........x^n,) Any (x,y,z,) can be measured within (x^n,y^n,z^n,)
Space being n-dimensional !
Space-Time being (x,y,z,)