What is Space Made Of? Exploring the Physical Components of the Universe

[alasange]

Hello, I'm not an academic but someone who had been watching way too many documentaries and has what is probably a very nieve question? "What is space made of?" It strikes me that in order for gravity or attraction of any sort to occur then there must be something physically linking the objects in question, whether that be energy or what? If that's right then that must be linking everything in every direction to everything else? In my simple mind it seems that if we can establish exactly what space and attraction are, how they actually work rather than just their consequences we might be better equipped to work out the big bang and beyond or is that overly simplistic and wrong? I keep hearing that gravity is a force and how it's measured but not exactly how one object attracts another. The membrane analogy doesn't seem to quite do it for me as it seems to be very 2 dimensional and doesn't adequately seem to translate into a full 3D environment, wouldn't you need infinite membranes eminating in all directive at once?

 

[fireflies]

Generally space is considered vacuum and made of nothing, conpletely empty as gravitation is zero there(considered). But in practical gravitation is zero nowhere, so space is not empty at all. (replied taking space as ordinary sense where space means = place above the atmosphere which is empty. But you can also say space holds stars, planets etc. in big sense!)

 

[fireflies]

And ofcourse force of gravitation
F=G##/frac{Mm}{r²}
When M,m are two masses and r is the distance between them. Even at infinty it is not zero, but the net force maybe zero.
Compare, net force may be zero but the density is never. It is very less but not completely empty

 

[phinds]

It strikes me that in order for gravity or attraction of any sort to occur then there must be something physically linking the objects in question, whether that be energy or what? If that's right then ...

It's not. There is no need for anything in order for gravity to work because gravity is just geometry, not a force. You hear it described as a force but that's classical mechanics which works really well on small scales (say a planet) but fails miserably on large scales (billions of light years) and near massive objects such as a black hole or a neutron star. Gravity is the geometry of space-time as explained by Einstein's theory of General Relativity.

Perhaps it will be easier for you to visualize thinking of magnetism, which IS a force. If you hold magnets close to each other you can feel the attraction or repulsion and that's true whether you do it in a vacuum or in air or in water.

 

[fireflies]

It's not. There is no need for anything in order for gravity to work because gravity is just geometry, not a force. You hear it described as a force but that's classical mechanics which works really well on small scales (say a planet) but fails miserably on large scales (billions of light years) and near massive objects such as a black hole or a neutron star. Gravity is the geometry of space-time as explained by Einstein's theory of General Relativity.

Perhaps it will be easier for you to visualize thinking of magnetism, which IS a force. If you hold magnets close to each other you can feel the attraction or repulsion and that's true whether you do it in a vacuum or in air or in water.

Further to that, if you think that what might actually carry gravitation then scientists think of graviton which acts as the carrier. But it's mostly quantum mechanics

 

[alasange]

It's not. There is no need for anything in order for gravity to work because gravity is just geometry, not a force. You hear it described as a force but that's classical mechanics which works really well on small scales (say a planet) but fails miserably on large scales (billions of light years) and near massive objects such as a black hole or a neutron star. Gravity is the geometry of space-time as explained by Einstein's theory of General Relativity.

Perhaps it will be easier for you to visualize thinking of magnetism, which IS a force. If you hold magnets close to each other you can feel the attraction or repulsion and that's true whether you do it in a vacuum or in air or in water.

Yeah but what I'm struggling with is how does a magnet attract or repel an object, I know you can measure it, predict it and quantify the force but how dies that force actually work at a quantum level? Similarly I've just started reading introductions to quantum physics (for beginners if you like? ) and have read that at those levels there are neutrinos or whatever that seem to communicate or influence reach other even though separated by vast distances? Sorry if I sound dim, I'm not a mathematician, physicist by any stretch of the imagination. But have really been interested by the concepts demonstrated in many documentaries I've seen recently. Many expressing theories to a degree but fail to show exactly how one object reaches out to another c to attract or repel it.

 

[alasange]

Yeah but what I'm struggling with is how does a magnet attract or repel an object, I know you can measure it, predict it and quantify the force but how dies that force actually work at a quantum level? Similarly I've just started reading introductions to quantum physics (for beginners if you like? ) and have read that at those levels there are neutrinos or whatever that seem to communicate or influence reach other even though separated by vast distances? Sorry if I sound dim, I'm not a mathematician, physicist by any stretch of the imagination. But have really been interested by the concepts demonstrated in many documentaries I've seen recently. Many expressing theories to a degree but fail to show exactly how one object reaches out to another c to attract or repel it.

Doesn't gravity apt to orbits? So surely it is a fierce of sorts even if only at that level? I've seen the common illustration of a planet on a sheet and the mad of the planet causes a depression in the sheet so that nearby objects then rotate around it which is simplistic but surely the sheet has substance to hold the planets up as it were and cause the angle that allows the smaller planet to circle it, I. Each. The membrane or sheet has substance?

 

[phinds]

Doesn't gravity apt to orbits? So surely it is a fierce of sorts even if only at that level? I've seen the common illustration of a planet on a sheet and the mad of the planet causes a depression in the sheet so that nearby objects then rotate around it which is simplistic but surely the sheet has substance to hold the planets up as it were and cause the angle that allows the smaller planet to circle it, I. Each. The membrane or sheet has substance?

The sheet is a rather poor analogy but somewhat shows the concept of space-time curvature. There IS no "substance", it's all just geometry. Google "geodesic" for further information.

 

[alasange]

The sheet is a rather poor analogy but somewhat shows the concept of space-time curvature. There IS not "substance", it's all just geometry. Google "geodesic" for further information.

Thank you. This is really interesting to me even if I don't know the maths or the language to articulate my interest or thoughts. This awful predictive text doesn't help! It's just that it strikes me, in my simplistic and nieve mind, that whether at the atomic level or the planetary level of one thing orbits another them there is a force, an attraction or indeed a repulsion that holds them often in equilibrium? Something in the space between them that's just strong enough to keep them together or enough apart to maintain the orbit. I'm interested to better understand what is in the space between actually doing this, not what it's called, measured or predicted but physically what is holding the two objects?

 

[phinds]

Thank you. This is really interesting to me even if I don't know the maths or the language to articulate my interest or thoughts. This awful predictive text doesn't help! It's just that it strikes me, in my simplistic and nieve mind, that whether at the atomic level or the planetary level of one thing orbits another them there is a force, an attraction or indeed a repulsion that holds them often in equilibrium? Something in the space between them that's just strong enough to keep them together or enough apart to maintain the orbit. I'm interested to better understand what is in the space between actually doing this, not what it's called, measured or predicted but physically what is holding the two objects?

It's a complicated dance. Mass tells space-time how to shape itself and space-time defines the geodesics along which stuff moves. You really need to get rid of this concept of "something in the space". I'll tell you just this one last time: there ISN'T anything there. I get that you are finding this hard to believe/comprehend, but that is the way it is.

EDIT: by the way, don't feel bad about finding this hard to "get". Newton didn't get it and basically just gave up. He couldn't explain what caused gravity, he just figured out how it works in practical terms. It took Einstein to figure it out.

Newtonian gravity "makes sense" because it works perfectly on the scale in which humans evolved, so it seems reasonable to us. There was never any survival value in understanding the concepts of General Relativity because they simply are not manifested in everyday life.

Planets travel in straight lines but the problem with that terminology is that we automatically use Euclidian geometry and "straight line" has a very well defined meaning and it just doesn't look like what a "straight line" in Reimann geometry (which described space-time) is, which is why we call travel in space-time "curved" even though it's really straight (a geodesic) in the sense that matters.

 

[Swami]

alasange, I recently found this video on youtube, which I think really helps with visualizing how the warping of space, rather than some active force between two objects, is what "binds" objects with gravity together, including planetary bodies.

https://www.youtube.com/watch?v=MTY1Kje0yLg

This should be contrasted with something like electromagnetism, in which force-carrying particles (called bosons) are actually "emitted." The interaction of those bosons is what causes the force between them, whereas gravity merely warps the space around a massive body with no exchange of particles between it and some other massive body.

Having said that, and also clarifying that I'm also no expert at all (just an interested layman, like yourself), I believe there is a competing theory explaining gravity. While gravity can be explained exclusively as the warping of space-time, some (I believe) claim that gravity actually is a force just like electromagnitism, etc. If this is the case, objects with mass would "emit" something called a graviton, which is also a boson like in electromagnetism, and that's what creates the force between two objects with mass.

I don't know if this is still a viable theory in physics, or if it's even in opposition to theories about warping space-time (both theories might be fully reconcilable with each other, for all I know).

Interestingly, the effects of gravity from a massive body "travel" at the speed of light. For example, if the sun were to disappear right now, we would not experience it for several minutes -- the same length of time it takes light to arrive from the sun. Likewise, the gravitational wave emitted from the black hole at the centre of the galaxy that keeps us bound to it is not an ongoing and immediate thing, but rather the gravity that's influencing our solar system at this very moment is actually tens of thousands of years old.

To explain this from the force-carrying graviton perspective, it's a predictable conclusion that gravitons travel at the speed of light. For the warping of space-time theory, it could be explained by space-time warping at a certain speed. Much as in the video above, removing a marble from the flexible sheet does not return the space to its regular, flat shape immediately, but takes time. So too would adding or removing a massive body require time for space-time to return to normal (a change in space-time requires a change in both space and time -- that seems reasonable to me). This latter explanation is fully my own thought-process on the matter, not something I'm aware of being argued by scholars of the field.

Anyway, I hope that at least gives some food for thought, though I'll again stress that I'm no expert in this.

 

[alasange]

It's a complicated dance. Mass tells space-time how to shape itself and space-time defines the geodesics along which stuff moves. You really need to get rid of this concept of "something in the space". I'll tell you just this one last time: there ISN'T anything there. I get that you are finding this hard to believe/comprehend, but that is the way it is.

EDIT: by the way, don't feel bad about finding this hard to "get". Newton didn't get it and basically just gave up. He couldn't explain what caused gravity, he just figured out how it works in practical terms. It took Einstein to figure it out.

Newtonian gravity "makes sense" because it works perfectly on the scale in which humans evolved, so it seems reasonable to us. There was never any survival value in understanding the concepts of General Relativity because they simply are not manifested in everyday life.

Planets travel in straight lines but the problem with that terminology is that we automatically use Euclidian geometry and "straight line" has a very well defined meaning and it just doesn't look like what a "straight line" in Reimann geometry (which described space-time) is, which is why we call travel in space-time "curved" even though it's really straight (a geodesic) in the sense that matters.

It's a complicated dance. Mass tells space-time how to shape itself and space-time defines the geodesics along which stuff moves. You really need to get rid of this concept of "something in the space". I'll tell you just this one last time: there ISN'T anything there. I get that you are finding this hard to believe/comprehend, but that is the way it is.

EDIT: by the way, don't feel bad about finding this hard to "get". Newton didn't get it and basically just gave up. He couldn't explain what caused gravity, he just figured out how it works in practical terms. It took Einstein to figure it out.

Newtonian gravity "makes sense" because it works perfectly on the scale in which humans evolved, so it seems reasonable to us. There was never any survival value in understanding the concepts of General Relativity because they simply are not manifested in everyday life.

Planets travel in straight lines but the problem with that terminology is that we automatically use Euclidian geometry and "straight line" has a very well defined meaning and it just doesn't look like what a "straight line" in Reimann geometry (which described space-time) is, which is why we call travel in space-time "curved" even though it's really straight (a geodesic) in the sense that matters.

Yeah i looked up geodesics,again little on the how or as you say how mass tells space time how to be or how spacetime defines geodesics. Lots of how to measure etc. I'm being too feel that no one actually knows the actual mechanics of these or the actual mechanics of forces like electromagnetic interaction and how they actually happen, how they attract or repel. Lots of, it's a force, an exchange of particles or how to quantify it. I've read in discussions on electromagnetics that some believe it's photons in high quantities, acting in my simple terms almost like a body of water between objects? I'm going to look at maxwell equations next and go back to my books, but even they state they don't know for instance at the quantum level how particles seem to communicate or effect each other at distance, hence my starting my journey to ask questions of others who might have an understanding. Thanks for your comments though

 

[A.T.]

alasange, I recently found this video on youtube,

Better forget it again. It's a bogus analogy, discussed many time here. For example:
https://www.physicsforums.com/threa...visualization-of-gravity.726837/#post-4597121

which I think really helps with visualizing how the warping of space, rather than some active force between two objects, is what "binds" objects with gravity together, including planetary bodies.

The warping of space doesn't do that. You need to consider space-time.

 

[Swami]

Thanks, A.T. -- those are really useful videos!

 

[alasange]

alasange, I recently found this video on youtube, which I think really helps with visualizing how the warping of space, rather than some active force between two objects, is what "binds" objects with gravity together, including planetary bodies.

https://www.youtube.com/watch?v=MTY1Kje0yLg

This should be contrasted with something like electromagnetism, in which force-carrying particles (called bosons) are actually "emitted." The interaction of those bosons is what causes the force between them, whereas gravity merely warps the space around a massive body with no exchange of particles between it and some other massive body.

Having said that, and also clarifying that I'm also no expert at all (just an interested layman, like yourself), I believe there is a competing theory explaining gravity. While gravity can be explained exclusively as the warping of space-time, some (I believe) claim that gravity actually is a force just like electromagnitism, etc. If this is the case, objects with mass would "emit" something called a graviton, which is also a boson like in electromagnetism, and that's what creates the force between two objects with mass.

I don't know if this is still a viable theory in physics, or if it's even in opposition to theories about warping space-time (both theories might be fully reconcilable with each other, for all I know).

Interestingly, the effects of gravity from a massive body "travel" at the speed of light. For example, if the sun were to disappear right now, we would not experience it for several minutes -- the same length of time it takes light to arrive from the sun. Likewise, the gravitational wave emitted from the black hole at the centre of the galaxy that keeps us bound to it is not an ongoing and immediate thing, but rather the gravity that's influencing our solar system at this very moment is actually tens of thousands of years old.

To explain this from the force-carrying graviton perspective, it's a predictable conclusion that gravitons travel at the speed of light. For the warping of space-time theory, it could be explained by space-time warping at a certain speed. Much as in the video above, removing a marble from the flexible sheet does not return the space to its regular, flat shape immediately, but takes time. So too would adding or removing a massive body require time for space-time to return to normal (a change in space-time requires a change in both space and time -- that seems reasonable to me). This latter explanation is fully my own thought-process on the matter, not something I'm aware of being argued by scholars of the field.

Anyway, I hope that at least gives some food for thought, though I'll again stress that I'm no expert in this.

Great thanks it has, but raised so many other questions! To my mind space time must have substance of some sort even if only at quantum level of it can be bent? If the bending of spacetime causes orbits then Why then do some objects move out of orbit despite the lack of obvious influence I. Each. Larger object? Example video is good but rather linear and 2D to my mind and doesn't explain how or why all systems seem to be flat in nature rather than a swirling ball of orbiting objects? Then I started thinking of black holes and wondering if they are indeed holes? All I've read seem to imply you'd fall into one and only be able to see a shaft of space as you liked over your shoulder? To my mind it makes more sense that they are 3 dimensional objects like planets but of infinite density and being drawn to one you'd still see the same view of space you had etc. My head hurts now! Lol

 

[phinds]

To my mind it makes more sense that they are 3 dimensional objects like planets but of infinite density

The reason we call the center of a black hole a "singularity" is because "infinite density" is non-physical and indicates a place where or math models no longer describe reality. You certainly will see "infinite density" in pop-science expositions, but that's just 'cause they think "math model breaks down" is too hard to explain.

 

[alasange]

The reason we call the center of a black hole a "singularity" is because "infinite density" is non-physical and indicates a place where or math models no longer describe reality. You certainly will see "infinite density" in pop-science expositions, but that's just 'cause they think "math model breaks down" is too hard to explain.

Do you think that for some reason space can only tolerate a certain amount of density, that at a certain point it explodes causing a big bang? Totally divergent from my initial post I know. On that being totally uneducated in all of this and in my simplistic world view I take the mechanical view. A winch on a land rover pulls a car out of mud, the cable connects them and is what is used to pull it out. Similarly a ram rod is used to repel objects, it's the rod that carries the force to move / push the object. That said I'm trying to uneerstand what the mechanics of attraction / forces actuality are (where that be magnetic,electro magnetic or whatever). Everything I've read tells how to measure or predict such forces but not what is actually happening, are particles of some sort connected, how is the magnet attracting the steel (I read they are swapping electrons, oppositely charged etc. But if you could magnify it or see in av different spectrum or whatever, what would you actually see, how or what connects them? )

 

[phinds]

Do you think that for some reason space can only tolerate a certain amount of density

As far as I am aware there is no reason to think so

... that at a certain point it explodes causing a big bang?

No one knows WHAT caused the beginning, which is why it is called the "big bang singularity". Again, "singularity" does not mean "point" it only means "the place where the math models show unphysical results and we don't know WHAT is going on".

Totally divergent from my initial post I know. On that being totally uneducated in all of this and in my simplistic world view I take the mechanical view. A winch on a land rover pulls a car out of mud, the cable connects them and is what is used to pull it out. Similarly a ram rod is used to repel objects, it's the rod that carries the force to move / push the object. That said I'm trying to uneerstand what the mechanics of attraction / forces actuality are (where that be magnetic,electro magnetic or whatever). Everything I've read tells how to measure or predict such forces but not what is actually happening, are particles of some sort connected, how is the magnet attracting the steel (I read they are swapping electrons, oppositely charged etc. But if you could magnify it or see in av different spectrum or whatever, what would you actually see, how or what connects them? )

 

[gmax137]

...That said I'm trying to uneerstand what the mechanics of attraction / forces actuality are (where that be magnetic,electro magnetic or whatever). Everything I've read tells how to measure or predict such forces but not what is actually happening...

This is where the physicists point out that physics is, in fact, about predicting not explaining. I know, not very satisfying is it? Actually a lot can be done by "mere" prediction. And really if you think about it hard enough, all "explanations" demand further explanations, it seems ultimately you get to a point where it is "turtles all the way down."

 

[Khashishi]

Do you think that for some reason space can only tolerate a certain amount of density, that at a certain point it explodes causing a big bang?

Actually, beyond a certain density, space collapses into a black hole. Or, if the density is high enough everywhere, the universe collapses into a big crunch. Those are the standard answers. Anything more gets you into highly speculative territory.

 

[jerromyjon]

"turtles all the way down."

...to the tetrahedral differential explanation? Would that make you "feel" any better about the universe? The fact that math can't elucidate or predict anything in this model doesn't allow it to be "science" which belongs on this forum but doesn't help you "feel" anything about the models. They just show what happens. This model says pretty much exactly what you want it to mean. Everything everywhere is linked by these inherently sufficient descriptions of everything down to the "atom" of atoms meaning the end of the turtles. This is it. We have all the answers to how the universe works... but it is worthless. With the knowledge that these tetrahedrons rule the universe and you cannot do a single thing to stop them what now?

 

[Dale]

It strikes me that in order for gravity or attraction of any sort to occur then there must be something physically linking the objects in question,

In modern physics theories the "something physically linking" different objects are called fields.

 

[Feeble Wonk]

I feel your pain alasange. I've struggled with this conceptual challenge for years.

In modern physics theories the "something physically linking" different objects are called fields.

I think Dale's statement here is as good as we're going to get though. Of course, the next question is... "WHAT" is the field composed of? Ultimately, you'll have to ask "WHAT" is energy? The deeper you look into theoretical physics, the more you will understand that these answers are not to be found. The science of physics is more informational... pattern recognition of logical relationships in observable parameters. You will not find resolution to your existential angst.

That said, I think it's interesting to follow the "field" concept with regard to "space". I've frequently seen references that suggest that the concept of "empty" space is meaningless, as there is always the quantum foam of vacuum energy, and virtual particles that pop into and out of existence. So, I'm curious... Is it reasonable to think of the quantum foam as being the "structural" component of spatial dimension?

 

[Dale]

the next question is... "WHAT" is the field composed of?

Why should the fields be composed of anything?

 

[Feeble Wonk]

I'm not suggesting that the mathematical construct of the field IS something. But I understand alasange's frustration. If the field has a material effect on physical action, I don't think it's unreasonable to expect it to have some type of substantive existence. Despite that, I recognize that it's not a realistic expectation.

Though, I am curious about my quantum foam question. Even as a mathematical construct, is the statement that space is never "empty" accurate?

 

[Dale]

If the field has a material effect on physical action, I don't think it's unreasonable to expect it to have some type of substantive existence.

I agree. But its existence is a different question than if it is composed of something else.

Existence and composition are not the same thing. Regardless of your philosophical stance on the existence of the field there is no good reason to assume that it is composed of something

 

[Feeble Wonk]

I agree. But its existence is a different question than if it is composed of something else.

LOL. This is going to turn into a semantic dispute, aside from the primary question. But, just for the sake of discussion, I am not suggesting that the field be composed of "something else". I would only expect it to BE "something"... to have some substantive existence by which it exerts physical action.

Regardless, that discussion quickly becomes philosophical. I'm more curious about the relationship between "space" and "quantum foam". Is ALL of space a distribution of the quantum "field" that manifests as the foam? Is that an accurate depiction of current consensus opinion?

 

[Feeble Wonk]

Generally space is considered vacuum and made of nothing, conpletely empty as gravitation is zero there(considered). But in practical gravitation is zero nowhere, so space is not empty at all.

In addition to whatever ambient gravitational field is present, if this theory would appear to suggest that "space" is never empty at all.

 

[Feeble Wonk]

In addition to whatever ambient gravitational field is present, if this theory would appear to suggest that "space" is never empty at all.

https://en.m.wikipedia.org/wiki/Quantum_foam

 

[arydberg]

Yeah i looked up geodesics,again little on the how or as you say how mass tells space time how to be or how spacetime defines geodesics. Lots of how to measure etc. I'm being too feel that no one actually knows the actual mechanics of these or the actual mechanics of forces like electromagnetic interaction and how they actually happen, how they attract or repel. Lots of, it's a force, an exchange of particles or how to quantify it. I've read in discussions on electromagnetics that some believe it's photons in high quantities, acting in my simple terms almost like a body of water between objects? I'm going to look at maxwell equations next and go back to my books, but even they state they don't know for instance at the quantum level how particles seem to communicate or effect each other at distance, hence my starting my journey to ask questions of others who might have an understanding. Thanks for your comments though

You are correct. in many areas we know many things but they are based on things we do not understand. if we stretch a rope we can send a pulse down it and the speed of that pulse is a function of its mass per unit length and it's tension. In the same way if we have air we can send sound waves in air and the speed of these waves is dependent on the density and pressure of the air. In a vacuum we can send light waves and they travel at speeds that are set by the electrical characteristics of the vacuum. These are called permittivity and permeability and they are electrical and magnetic in nature. But there is nothing there? It is all very strange. There is a lot we do not know. btw in all cases the equation for the velocity in a medium are similar . rope v = square root ( Tension/massper unit length) air v = square root (pressure / density) and in a vacuum the speed of light is = C = square root ( 1 / permeability * permittivity ). it sort of looks like we need a term like of looks like either 1/permeability or 1/ permittivity.

 

[Dale]

I am not suggesting that the field be composed of "something else".

Oh. That is what I thought you were suggesting with:

the next question is... "WHAT" is the field composed of?

My response was only intended to point out that while there are good reasons to assume that interactions are mediated by something there are not (to my knowledge) good reasons to assume that fields are composed of anything.

Regarding "quantum foam", I don't have an opinion on your question.

 

[Feeble Wonk]

My response was only intended to point out that while there are good reasons to assume that interactions are mediated by something there are not (to my knowledge) good reasons to assume that fields are composed of anything.

I didn't mean for this to become at all argumentative Dale. I recognize that quantum field theory is a formalistic mathematical model... like any field theory I guess... and is not intended to describe physical "reality" (whatever that is). Yet, I was simply trying to offer sympathy for alasange's conceptual struggle expressed in his original post.

...It strikes me that in order for gravity or attraction of any sort to occur then there must be something physically linking the objects in question, whether that be energy or what? If that's right then that must be linking everything in every direction to everything else? In my simple mind it seems that if we can establish exactly what space and attraction are, how they actually work rather than just their consequences we might be better equipped to work out the big bang and beyond or is that overly simplistic and wrong?...

While frustrating for the professional/academic physicists, I don't believe alasange's question is at all "simple minded", as he feared. Particularly to the interested lay person, there is a reasonable (while possibly naive) expectation that the science of physics describes something "real"... tangible and substantive... that actually exists. They expect "forces" of attraction or repulsion to be applied by some type of material contact with whatever is translating the force.

Generally space is considered vacuum and made of nothing, conpletely empty as gravitation is zero there(considered)...

...There is no need for anything in order for gravity to work because gravity is just geometry, not a force. You hear it described as a force but that's classical mechanics which works really well on small scales (say a planet) but fails miserably on large scales (billions of light years) and near massive objects such as a black hole or a neutron star. Gravity is the geometry of space-time as explained by Einstein's theory of General Relativity.

The lay person's confusion and frustration becomes even more pronounced by these kinds of references. Because, while the nothingness of "empty" space is easy enough to conceptualize, NOTHING is not something that can bend, expand or contract... unless you are limiting the description to a purely abstract mathematical/geometrical description. And, it is very difficult to understand how a force of ANY kind can be translated via "nothing".

In modern physics theories the "something physically linking" different objects are called fields.

This image would appear to be much more helpful, because it offers the conceptual vehicle by which a force can be translated, and provides a mental construct of something that can have a shape to bend or expand.
But, as I said before... If the field is thought of as the "something physically linking" different objects, then it is reasonable (I think anyway) to ask WHAT the substance of that "linkage" is, aside from the mathematical description of the variable field strength over spatial dimension.

https://en.m.wikipedia.org/wiki/Quantum_foam
I think the mental image of the quantum foam (or "space-time foam") described in this link is similarly helpful in that it offers a "substance" of spatial dimension. Yet, it too ultimately fails to explain "what" the foam actually IS ontologically.

So, alasange... I'm sorry, but I'm afraid gmax's statement here pretty much sums it all up.

This is where the physicists point out that physics is, in fact, about predicting not explaining. I know, not very satisfying is it? Actually a lot can be done by "mere" prediction. And really if you think about it hard enough, all "explanations" demand further explanations, it seems ultimately you get to a point where it is "turtles all the way down."

 

[phinds]

The lay person's confusion and frustration becomes even more pronounced by these kinds of references. Because, while the nothingness of "empty" space is easy enough to conceptualize, NOTHING is not something that can bend, expand or contract... unless you are limiting the description to a purely abstract mathematical/geometrical description. And, it is very difficult to understand how a force of ANY kind can be translated via "nothing".

Right. The problem is that we say "curved" or "bent" because we are using the language of Euclidean geometry and using Euclidean straight lines as the reference. In the Riemann geometry of space-time it's NOT bent, it's a straight line (a geodesic). This just isn't something that the lay person is ready for right off the bat.

 

[Dale]

I recognize that quantum field theory is a formalistic mathematical model. like any field theory I guess... and is not intended to describe physical "reality" (whatever that is).

This kind of language always gets my "alert" up. It is usually used by crackpots who are attempting to discredit a theory that they don't like as being nothing more than math. I am not saying that that is what you are, but you should be aware that that is the attitude conveyed by this type of statement.

A theory of physics consists of both a mathematical model as well as a mapping from that mathematical model to the results of experimental measurements. QFT consists of both the mathematical model and also the correspondence to real-world experimental outcomes. So your description is misleading at best.

That mapping from the mathematical model to experimental results has been verified to the best precision known to man.

If the field is thought of as the "something physically linking" different objects, then it is reasonable (I think anyway) to ask WHAT the substance of that "linkage" is

The fields themselves are the substance of the linkage. The idea that some other substance is required is neither logically necessary nor experimentally motivated. This assumption is what I was objecting to above.

 

[Feeble Wonk]

I'm really not trying to be controversial Dale, and I regret that my characterization of QFT came across as being "misleading at best".

I certainly was not trying to discredit QFT, or quantum theory in general. On the contrary, the remarkable thing about quantum theory is that it has been so convincingly verified by experimentation. Regardless of how counterintuitive some of the implications might seem, physical existence is clearly quantized at a fundamental level.

Further, I was definitely not attempting to suggest that physical theories are "nothing more than math". Yes, these theories are written in the language of mathematical formalism. However, the theories are typically arrived at initially by recognizing patterns of action within observable physical parameters, elucidating the logical relationships between those physical parameters, and then utilizing the theory to make predictions that can be verified experimentally. The theories are also obviously much more than "just math" because their power of predictability allows for real world application of the physical principles in question. In the case of quantum theory alone, the real world applications include lasers, CDs/DVDs, MRI diagnostic imaging, and countless others.

Yet, despite the compelling degree of experimental verification, and despite the incredible value in real world application, I think you'll agree that there is still great debate within the physics community regarding the appropriate interpretation of quantum theory... debate about what's really going on at the quantum level. Still, the debate is largely philosophical, because the predictions of quantum theory remain the same regardless of whatever interpretation you might favor. That is precisely why the "shut up and calculate" attitude is so prevalent in practitioners of quantum theory.

My impression was that the OPs curiosity was similar to this. He (or she) seemed to be asking for an "ontological" definition of "what" space is. I thought your reference to "field" theory was helpful in that it at least offers a mental construct to visualize, but I don't believe it really gets to the heart of the OP's question unless you can define what the field is ontologically.

I do not mean for this to be at all confrontational, and I don't believe it is an overly controversial statement. I'm not even sure that we are in actual disagreement. I think your objection to my previous statement might be largely due to some loose semantics on my part. I did not mean to suggest that a field's "substance" of linkage should be thought of as some type of mystical "luminiferous ether". You stated yourself that "there are good reasons to assume that interactions (in/of/by the field) are mediated by something". That "something" is all I meant by the "substance" of linkage.

Yet, the interested lay person (reasonably, but naively) expects physics to be able tell them, in ontological terms, WHAT that "something" is. I was simply trying to explain to alasange that, ultimately, the science of physics does not provide those types of answers to those types of questions. Those kinds of questions are left to the philosophers.

Again, I think gmax summarized that position much better, and much more succinctly...

This is where the physicists point out that physics is, in fact, about predicting not explaining. I know, not very satisfying is it? Actually a lot can be done by "mere" prediction. And really if you think about it hard enough, all "explanations" demand further explanations, it seems ultimately you get to a point where it is "turtles all the way down."