SPACE IS NOT A THING: SUMMATION
Premise: Space is NOT a thing. Space has no structure or substance. Space is a mental concept of the human mind that we use to picture the imaginary container real stuff resides in. I find no credibility in the alternative, that space-is-a-thing with structure and substance. Why?
Every experiment has failed to show evidence for space-as-a-thing.
But the big no-no is that space-as-a-thing violates the First Law of Thermodynamics. If the standard model of cosmology is correct, then the Big Bang event created space-as-a-thing from scratch; from absolutely nothing. Though postulated as a given, no one has yet to come up with a adequate or even credible how that happened or even could happen. Worse, that process is ongoing. Recall that the late Sir Fred Hoyle was bucketed for advocating the Steady State Universe which required the creation of matter from nothing - something like one atom of hydrogen per cubic mile per year or some such order of magnitude figure akin to that. Hoyle could give no mechanism. Of course his retort was that the alternate Big Bang event created everything from nothing all at once, again without any mechanism given, but that was apparently okay while his creation from nothing wasn't. Well creation from nothing is NOT okay in any cosmology.
I really have to admire the audicity of some cosmologists in their popular writings. In one chapter they will state the First Law of Thermodynamics about how energy (hence matter) cannot be created or destroyed but only changed from one form into another. In other words, there is no such thing as a cosmic free lunch; you can't create something from nothing. Yet in another chapter they will note how the energy density of the cosmos is unchanging or how it is a constant, even though the Universe is expanding. That immediately contradicts the First Law of Thermodynamics. Since space-as-a-thing translates into the creation of dark energy and dark energy translates back into the creation of space-as-a-thing (each creating more of the other out of absolutely nothing) that's a free cosmic lunch. They - cosmologists - contradict themselves. If they don't realise they've done it, they don't deserve to be in academica. If they realise this contradiction without commenting on same, they deserve to be kicked out of academica.
So if you are advocating space-as-a-thing then you are advocating the creation of something from nothing therefore advocating that the First Law of Thermodynamics is being negated even as I write and as you read. Good luck with that premise.
Motion, and variations thereof (acceleration, decelleration, momentum, rotation, etc.) is entirely independent of space-as-a-thing or even of space-as-a-not-thing. Recall that famous early 20th Century "New York Times" editorial that rocket travel was pure bunk on the grounds that in space there was nothing for the rocket's exhaust to push against. That editorial was retracted on the day of the Moon landing! So space travel via rocketship is possible even if space is NOT a thing since all relevant forces operate independently of the existence or non-existence of space. If one persists in trying to link motion and space-as-a-thing, find an equation that involves motion that also has space-as-a-thing as one of the required parametres.
Twenty Questions (give or take): If space-is-a-thing...
Why the phrase "the vacuum of space"? What 'thing' do you have to remove from space in order to achieve a perfect vacuum? What is the 'thing' composed of? What is its chemistry? Since it is right in front of your nose, what does it smell like? Could you stick out your tounge and tase the 'thing' that makes space a thing? What other properties does it have that you (or instrumentation) can detect? What are the associated particles, forces and fields that make space-as-a-thing strut its stuff? What is the density of space? If space has a density then could we in theory fly like a bird to the Moon if we could construct a pair of wings large enough? How does space-as-a-thing alter the standard model of particle physics? Would the Universe be any different today if the thing-ness of space had never existed? If so, how would it be different and if that were the case might you not even be here to worry about it? In other words, is the thing-ness of space required or vital for your own existence? Could we with our advanced technologies change the nature of that 'thing' property of space by some physical process or other? Is the thing-ness of space a resource that we could make use of akin to how we could mine the asteroid belt for resources? The speed-of-light is slower in glass than in water, and slower in water than in air and slower in air than in space, so if space is a thing would the speed-of-light be even faster than it is now if you could remove the thing-ness from space?
Anyone who advocates that space-is-a-thing has to wear the burden of proof on their shoulders and provide at least some solid slab-in-the-lab evidence. Either that or they should cease prattling on about it as if the concept of space-as-a-thing was set in stone and the matter of the nature of space was now settled for all eternity. It's not settled.
John Prytz