Can space be compressed? Or merely substances in space? There is a theory of FTL travel which involves compressing spacetime before the moving vehicle.

Doesn't substance in space have space in the sense of extension? Spatial things in space. But if space was infinitely compact how could it expand or be anything other than it is??

Let me put it this way? If we have space infinitely compact, it is infinite so how can it expand and add more infinity to what it is from itself?

Space is an aspect of the real world that's closest to nothing. Some people describe a sense of liberation when they're in the wide plains of the steppes or savannahs, flatland stretching from horizon to horizon - they feel like, inter alia, mounting a horse and riding, just riding it...forever.

While space as in outer space does evoke in us a sense of exploration, it comes not with the feeling of being set free but with that of being lost and alone in the cold and dark vastness of the void.

Infinity, I sense, is somewhere in there - as you get on the horse and look out and realize that the land stretches out as far as the eye can see and beyond...

My space is my freedom, My limitation is my $\infty$.

Space is also inherently continuous (inside), just as it captures all reality in its hands (outside). The community of all points forms finite spatial objects but space itself is only continuous by being differentiated by its points, which are nothing. Space and continuous mean the same thing to me. All space is infinitely dense, so maybe space naturally expands

Space — Gregory

There is no space as a place; the quantum fields exhaust reality.

Isn't space just an observable lack of things in a select parameter? I wouldn't see how its infinite malleability would affect its physical properties. I mean, I can divide a chocolate chip cookie infinitely.
That wouldn't necessarily mean its infinite, nor would that make the finiteness of its particles chaotic.

I wouldn't necessarily think so anyway.

Space is also inherently continuous (inside), just as it captures all reality in its hands (outside). The community of all points forms finite spatial objects but space itself is only continuous by being differentiated by its points, which are nothing. Space and continuous mean the same thing to me. All space is infinitely dense, so maybe space naturally expands — Gregory

Perhaps...

In 1D, points are an issue since they're zero dimensional. How can any number of nothings (points) add up to something ( length)?

In 2D and higher dimensions, space is less problematic as the boundaries of any given area/volume are not points but either lines/faces.

From Wikipedia:

Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a hard vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays

Is not the only thing conceivable as physically existing something that is spatial?

A finite piece of space is infinite in it's compactness. There can be space without matter but no matter without space. Objects are spatial and infinitely compact in their spatial element I'm thinking

Is not the only thing conceivable as physically existing something that is spatial? — Gregory

The quantum vacuum with its overall quantum field is the One and Only, as the simplest state. Its field waves provide for extension into dimension, and it is everywhere because 'Nothing' cannot be. There's no non acting and unresponsive space background as a place, as Newton had it, whose only quantity is volume.

Matter is composed of field.

It seems most natural to me to think of space as infinite. — Gregory

It is my understanding that the universe is generally seen as finite but unbounded. The analog often used is a sphere. If we were on the surface, which we are, we could walk forever without ever getting to an edge.

There is no end to how small something can shrink. — Gregory

It is also my understanding that the universe is hypothesized to be granular at a sub-sub-sub-sub atomic level. The planck length, 1.616255(18)×10−35 m, is considered by some to be the smallest meaningful dimension of space.

Space is part of us and we are made of it. It doesn't mean we own space but space is all we cannot control space only G-d can but we can use space for us to exist.

At the back it has to expand. But how can this be? How can space be distorted near mass? How can space expand? You can simply state that the metric is changing, but that begs the question. What Einstein offered no explanation for was how mass curved spacetime. It merely stated that it accompanies mass. The how of the metric change remains unclear, and even gravitons fail.

In 2D and higher dimensions, space is less problematic as the boundaries of any given area/volume are not points but either lines/faces. — TheMadFool

This is just as problematic. How do you put an infinity of lines together to get a 2d whole? The problem lies in the decomposition itself. When you cut a line, a plane, a volume up, it will cost you an infinite amount of time before the cutting is done. After the cutting you have taken away an èssential part. The connection. If the cut is symmetrc, theCan one bring back the connection by simply putting the two pieces back together? Will they magically form a whole again? Can the cut be reversed? No. Every time you cut, be it a line, a plane, or a volume, you take away a point, a line, or a plane, and if you do that an infinite number of times you take away an infinity of points (which are the boundaries of closed pieces of lines, ĺike a line lies at the boundary of a 2d structure; the point is the only one in the family that has itself as a boundary). So if you cut a line than by definition the connection point is lost. It doesn"t belong anymore to the two pieces by symmetry. It can't belong to both so it belongs to neither. so it belongs to neither. So if you cut up a ĺine, you basicaly cut it away. You can add a point after each cut. But the cut isn't undone by that. It's permanent. Two pieces of line can't form a whole anymore. You need glue that doesn't exist. If it existed you would see the point where you fixed the whole. A point is the only dimension you can't cut up.

There is no space as a place; the quantum fields exhaust reality. — PoeticUniverse

Fields need space though to express their totality. Even the virtual ones. That's why graviton fields offer problems, as they carry information about the very space they travel in.

It is also my understanding that the universe is hypothesized to be granular at a sub-sub-sub-sub atomic level. The planck length, 1.616255(18)×10−35 m, — T Clark

That's popular science, which is maybe the best suited for this forum.There is indeed a combination of physical constants (h, c, and G) that gives rise to that lengthscale but that doesn't mean space is not continuous beneath that scales. What would it even mean that it is not meaningful? That there are no sub-points? That volòme and surface have an arbitrary relation? Ĺike fixed closed line can contain an infinity of areas, or a fixed area an infinity of containing lines? And what about time? Should that be granular too because of that?

From Wikipedia:

Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a hard vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays — jgill

What do you think is meant by "hard vacuum" here? Is that as distinguished from a "soft vacuum"?

It is also my understanding that the universe is hypothesized to be granular at a sub-sub-sub-sub atomic level. The planck length, 1.616255(18)×10−35 m, is considered by some to be the smallest meaningful dimension of space. — T Clark

That's the case according to loop quantum gravity. According to general relativity and string theory it's continuous.

The reason I say matter is infinitely compact is that holes in it, however small, is space and so all the matter by default has no holes.

I'm not sure what fields mean if they are not spatial. The very word implies space

Space is that which is not there. When we give something which is not there a name, such as space, the name itself implies that there is something there, which we are naming. Words are like a finger pointing, but if the word is pointing at nothing, how is one supposed to see the emptiness?

There is indeed a combination of physical constants (h, c, and G) that gives rise to that lengthscale but that doesn't mean space is not continuous beneath that scales. — Cartuna

That's the case according to loop quantum gravity. According to general relativity and string theory it's continuous. — Michael

I identified it as a hypothesis, not a fact. The explanation I found indicates that below that size, addition of energy, as would be required to take a measurement, would cause a black hole to form. My point was that it is not yet established that space is continuous at all scales.

That's popular science, which is maybe the best suited for this forum. — Cartuna

Another good reason not to communicate with you any further.

"Hard vacuum and soft vacuum are terms that are defined with a dividing line defined differently by different sources, such as 1 Torr,[43][44] or 0.1 Torr,[45] the common denominator being that a hard vacuum is a higher vacuum than a soft one." :chin:

↪jgill
At the back it has to expand. But how can this be? How can space be distorted near mass? — Cartuna

Can space by itself be distorted? Without its connection to time. :chin:

Why would one think "space" has only one meaning?

My question is to you and any other member who knows better.

Does Space actually exists? I mean out of human experience that we understand it, does it actually exist "on its own"? Or it's only an a priori human non empirical thing which allows us to form all of our experiences as Kant suggested?

In fact are there any scientific final answers for that supporting or rejecting Space definition of Kant? Or is it still an open issue?
I might did poorly research on the Internet but I didn't find any convincing scientific answer in favor or against that. I haven't been able to form an opinion about it yet.

I'd define space as that which everything moves through. There doesn't have to be infinite containers as Zeno thought. There is something which can have things in it without losing anything of itself and we have called this space for thousands of years

Does Space actually exists? I mean out of human experience that we understand it, does it actually exist "on its own"? Or it's only an a priori human non empirical thing which allows us to form all of our experiences as Kant suggested? — dimosthenis9

This could be if our brains spatialize time into ‘space’ so that we can better navigate through the series of discrete nows. The brain’s re-presentation of the successives would add spatial dimension to the past nows, this spatializing showing up as a distance for what is really just back in time

I'd define space as that which everything moves through. — Gregory

Except that this inert absolute space of Newton's got the boot from Einstein, whose gravitational field essentially is space-time at the macro level. At the micro level, the quantum field would serve as 'space', although it is really just simple continuous stuff. One could still say that an elementary particle as a field quantum is in the field.

Space and infinity are some of my favorite ideas, and they seem to naturally go together when we consider the universe. If there were a limit to the universe we could go to the edge and point, asking "how far is that way?" It seems most natural to me to think of space as infinite. And actually it seems to be infinite in opposite infinite ways. There is no end to how small something can shrink. And if I hop towards a limit, there are always infinite sub-steps. So infinity as space seems to be the ground of everything and "what is finite itself" adds form to the chaos. In the end, the world will always seem paradoxical because it has a paradoxically at it's root. What I'd like to know is whether space existing in all possible place is just the mirror image of space being infinitely divisible — Gregory

sounds like your talking about god

So the hard vacuum does a better job cleaning the rug.