Is spacetime concrete, abstract or both?

Question

The last option suggests that at a fundamental level there is no distinction between real concrete stuff and abstraction. Here is my point. Einstein General Relativity says that spacetime is more like real stuff, because it follows its own equation. Non uniform motion (for example of a spinning object) must exist in relation to spacetime, some real stuff. Yet, it is conceptually very difficult to consider that spacetime in itself is real stuff. Usually, we think that the stuff that progresses in time is what is real, whereas past and future and even time itself are concepts. In other words, we think of spacetime as an abstraction that is required to express the relationships between events. Are these two views inconsistent? Maybe not. After all, through physics we tried to find the "real concrete stuff" out there and we found that it is an abstraction only created when we observe. So, why not considering that the intelligent laws, abstraction, spacetime, etc, is what is real?

I understand that in the standard paradigm concrete and abstract are considered as opposite and therefore something cannot be both abstract and concrete, except from different reference points. However, physics has so often made obsolete standard concepts. My question is whether physics has simply made obsolete the concepts of abstract and concrete as being opposite
and that, from this single new reference point, spacetime would be both abstract and concrete.

Some answers emphasize that spacetime is concrete, real, etc. They also point out that spacetime is abstract because it is hard to understand and more subtle than the objects of the senses, which we are used to consider as concrete. One might think that spacetime or the ultimate reality from which it emerges is the new concrete. This ultimate reality would only be said to be abstract relatively to the old concrete, the object of the senses. The division between abstract and concrete would still exist at a more fundamental level, and spacetime would not really be abstract in this new division. For me, this would be a way to say that spacetime is concrete, not abstract. What I wanted to suggest by the third option is that spacetime is abstract in a fundamental way, as abstract as anything could be abstract, and yet concrete. This level of abstraction could emerge from a more fundamental level of abstraction, but this would not make it at all non abstract. No division!

Answer 1

Depending on your reference point it could be either, but not both. ~

Answer 2

There is more to this universe than meets the eye.

Space is as real as any material object you can touch, see, smell, hear, or taste. Just because our senses cannot somehow sense space, does not mean it does not exist as a real entity. It simply means our senses are limited. And, as the definition for "abstract" is...

"Considered apart from concrete existence: an abstract concept.
Not applied or practical; theoretical. See synonyms at theoretical.
Difficult to understand; abstruse: abstract philosophical problems" [See source.]

...that would make space abstract. It's abstract because it is less than "concrete" and it is certainly difficult to understand.

But it does not make it less real. For example, we can observe the effect of massive gravity on space itself. This is manifest in the so-called gravity lenses that have been observed around massive galaxies. So gravity acts on space something like it acts on mass. [See source.]

Further, space itself is expanding. Hubble found this in the so-called red shift of the galaxies. That is, the expansion of space, our known universe, has been measured...it is a fact. It is real.

Finally, our space can be defined by x,y,z,t coordinates; where t is time and the other variables are the three static dimensions of space. If space were not real, these dimensions would simply be constructs of the human mind. Physical things could not really happen to them.

Yet, hey, if a spaceship approaches the speed of light in the x direction, for example, x begins to shrink when observed from outside the ship. Something physical happens to the dimension, to the x part of space. Space is as real as you are.

Space is abstract because our limited senses cannot sense its true physical nature. But we can see it is nonetheless real because physical things happen to it when acted on by extreme effects...like massive gravity and extreme speeds.