What Are the Physical Components of Space?

[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."

 

[Dale]

the debate is largely philosophical

Yes, the choice of interpretation is entirely philosophical, although for QM the scientific community pays slightly more attention to the debate than in most other branches of physics.

I don't believe it really gets to the heart of the OP's question unless you can define what the field is ontologically.

You may be right, but let's let the OP clarify. I did not get that impression. If he is indeed interested in the philosophy then this isn't the correct forum for the discussion. Philosophical discussions are usually avoided here, for very good reasons.

Yet, the interested lay person (reasonably, but naively) expects physics to be able tell them, in ontological terms, WHAT that "something" is.

In scientific terms that something is the fields, there is no logical or experimental need for anything more.

If someone wants a philosophical answer then they need to ask a philosopher, not a scientist. We should restrict the conversation here to the science, not push it into an unnecessary philosophical discussion which will need to be closed.

 

[Feeble Wonk]

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.

I should drop it at this point, but I can't help wondering if you find this explanation less objectionable.

 

[Feeble Wonk]

Never mind... Our posts crossed on the net.

 

[russ_watters]

I think the problem is that because we all view the world macroscopically, laypeople are used to the idea that forces and waves involve physical substances in physical contact with each other. That's what makes analogies like the rubber sheet analogy so useful: they speak to such prejudices. But it is also a prejudice that is tough to overcome.

 

[Feeble Wonk]

<<philosophy paper link deleted>>

I offer this paper as an example of why it is challenging for even a well educated lay person to visualize a quantum field as being an objective entity, in and of itself. I would argue that the vast majority of lay people expect physics to convey a "traditionally realistic" description of physical existence, and are confused and frustrated when that is not the case.

 

[Dale]

To the OP, if you are interested in a scientific discussion then please PM me and I will re-open the thread. The philosophical discussion is closed.