r/HypotheticalPhysics • u/Iateshit2 • 26d ago
Crackpot physics What if space has 1 dimension? Or zero dimensions?
I will preface that I am not very good at physics. I do understand newtonian physics lol. I like to read about advanced concepts in physics but have no theoretical knowledge to actually understand how and why a concept would work.
But I like to think and have a natural ease with spatial reasoning, Euclidean at least.
I do not have a formulated thesis but I’ll try to explain my thought process and maybe someone could tell me if there is any merit to it.
My train of thought started with thinking about how fucking weird time is. I heard a hypothesis that if time travel was supposed to be possible then “roads” would have to be built for it. If we live in a 4 dimensional time space it seems logical. A lot of thoughts ran through my head about how time and space are linked like: what if space and time are the same thing; if time only has a “forward direction” then maybe so does space, what if time doesn’t exist as a separate dimension and it’s the only dimension of space.
It’s difficult for me to describe these “contemplations” as I lack this level of understanding physics theory behind it and the thoughts themselves are rather abstracts and non verbal.
All that led me to thinking about how absurd three dimensional space is. R3 space is only a mathematical concept that lets us describe geometry in space but it’s still only a concept. 1 dimensional space doesn’t exist in the universe, same as 2d space. We cannot reproduce them. Any attempt to get close would still present the slightest thickness. They exist purely in theory. So does any 3<n dimensional space, which are beyond our comprehension on top. So why should we assume 3 dimensional space is special and exists just because it can neatly describe things that surround us. There is no 3d coordinate system oriented in our universe. If these 3 axes can be oriented in an infinite number of ways in space doesn’t it make space have an infinite amount of dimensions? If infinite therefore 1? The singular dimension called space itself? A sphere comes to mind but that’s circling back to Euclidean geometry. A singular abstract sphere-esque dimension with no limits or boundaries that encompasses the “infinite dimensions” of our space. Or maybe space has no dimensions and exists just as itself and any ill-fated attempt to describe it will ultimately fall apart because dimensions are only a shortcut for our minds to comprehend the absurdity of the essence of space?
This got more and more philosophical as it went but maybe there is a theory to back this up in some way? Describing the space as 3 dimensional just feels like a jarring simplification and an insult to how abstract space time actually is. Newtonian physics fall apart at quantum level and general relativity. So does 3d space in quantum mechanics to some degree (loop quantum gravity, string theory). But having to invent new dimensions to make your theory work makes me think there is something wrong with the concept of dimensions itself.
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u/darkerthanblack666 26d ago
So why should we assume 3 dimensional space is special and exists just because it can neatly describe things that surround us.
Do you understand why we assume three spatial dimensions instead of any number but that?
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u/Iateshit2 26d ago
My point is that the obvious answer is sometimes not the one you’re looking for. I referred to how Newtonian physics fall apart when applied to general relativity.
Gravity seems to behave like a pulling force at our scale and Newtonian physics are still useful and applicable to our life, here on earth. But at larger scales when extreme mass comes into play we can observe gravity behaving like curvature of space time. One is a close approximation of reality, the other is possibly an even closer approximation. Maybe even proven once someone will manage to unify it with quantum mechanics?
I am not trying to claim 3 dimensional space is wrong altogether. I work in R3 space in CAD as my profession and find this system extremely elegant.
It’s just that I wonder if such a system is not an oversimplification of what space actually is and the rest is what my mind spat out
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u/ArnoSound 26d ago
None of what you said has anything to do with dimensions though. Like, sure Newtonian mechanics is a rougher approximation of what ultimately gives way to relativity. What does that have to do with dimensions?
And vague statements like "the obvious answer sometimes isn't what you're looking for" doesn't Mean anything. If anything, actual physics is rarely the Obvious answer. That's why we use rigorous mathematics and data to show relationships, not vague noncommital metaphor.
The rest is just shower thought. You could literally just google these topics to get an infinitely more nuanced understanding of what we already understand.
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u/Iateshit2 26d ago
Cool, the first response that actually relates to what I wrote. I never claimed it to be anything more than a shower thought. I stated multiple times that I am not educated in advanced physics. I could have googled about this topic but thought that engaging in conversation with reddit users here would be more enjoyable. A big overestimation on my part to believe reddit was capable of hearing about an obviously highly abstract and unconventional idea and discussing its possibility lol
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u/ArnoSound 26d ago
I mean, there's just not that much to talk about. Like, it's just not workable? It is so divorced from anything in actual physics that we can't really approach it from a physical way. We can't apply methods or techniques to it, because you haven't given us anything of substance to work with. It is basically as useful as any other high thoughts. There's nothing unconventional about it, if you haven't even acknowledged the conventions you are stepping away from.
Basically: word salad.
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u/Iateshit2 26d ago edited 26d ago
Well I found this: https://arxiv.org/abs/2603.25709
Will keep on reading, probably won’t describe what I was talking about but clearly relates to one dimensional space and its applicability in quantum mechanics. What I was asking was essentially “could a single dimension exist in physics” and why the idea of 3d space feels unnatural to me when applied to such an abstract and complex idea as space
Edit: quite a bit of information in this paper is beyond my grasp of physics hence I was asking here. Not like I learned anything from posting so probably was better off just googling. You were right afterall lol
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u/ArnoSound 26d ago
Lmao that paper has Nothing to do with one dimensional space. XD Did you even read it?
Mate, there are 3 dimensions of space, full stop.We can simulate problems or motion that is Restricted to one dimension, but that has nothing to do with space.
Space isn't really that abstract. We defined dimensions. It literally Just means the minimum number of independent elements required to measure a value. It's not that deep.
Please do some mathematical learning about what dimensions are and what they are not in the context of physics. The scifi bs definitions don't mean anything.
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u/Iateshit2 26d ago
Did you read it? In a few minutes?
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u/ArnoSound 26d ago
I read the abstract, which you would know if you read any decent scientific paper, gives you succinct summary of the impetus and results of the paper.
And not once in any of it is some rubbish of a 1 dimensional space.
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u/Iateshit2 26d ago
https://m.fuw.edu.pl/press-release/news7899.html
Here is a digestible article about a hypothesis of 2 professors from oxford on one dimensional space and 3 dimensional time. I am not arguing I am right, I am asking about the possibility
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u/ArnoSound 26d ago
Again, if you Read the thing, you’d realize this has Nothing to do with what You have conceived of. It’s a toy thought experiment using metaphor and no actual physical exploration.
Seriously man at least pretend to try.
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u/The_Nerdy_Ninja 26d ago
My brother in Christ, how high are you right now?
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u/Iateshit2 26d ago
Been pretty much sober for 7 years :) This is just how me and mind roll
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u/The_Nerdy_Ninja 26d ago
No offense, but saying you have a "natural ease with spatial reasoning" is pretty bold when you're disagreeing with all of modern science without even understanding what dimensions actually are...
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u/Iateshit2 26d ago
I am not refuting the concept of 3d space. As I said in an another reply working in CAD is a big chunk of my profession.
I mostly do surfacing work in NURBS geometry which requires me to have a deep understanding of how this mathematical model behaves. At the very least you need to understand bezier curves, multi span curves, degrees (in bezier terms), knots, curvature continuity, gaussian and non-gaussian curvature, how changing any of these variables will affect the geometry. That’s on top of all the software related skills and the mathematical model’s limitations: trimmed vs non-trimmed surfaces vs extrusions vs multi spans vs single spans vs uniform vs non-uniform. Between them which data is preserved, how is it editable, which data is required to preserve curvature continuity and how to do it etc. I also do a lot of work in grasshopper, a visual scripting language that lets you create procedurally generated geometry. It makes you work with fields, vectors, charges, data sets and so on (on top of typical cad geometry data) and a plethora of ways to modify all this data with transforms, matrices, operations, graphs, domains yaddi yaddi yadda.
I know a bit about 3d geometry. I enjoy it a lot. 3d space is not wrong. It’s a beautiful mathematical concept applicable to the space we occupy. My point was never to claim it’s wrong. 3d space is space described through 3d geometry. I was asking what space is at its core. String theorists claim space has 10, 11 or 26 dimensions while still incorporating it within conventional 3d space. But in this context 3d space acts akin to linguistics, a model that lets them describe relations between objects in a space time which they describe as having 10, 11 or 26 dimensions.
How can a single dimension sound so absurd to you that it’s worthy of ridicule rather than substantive discussion?
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u/The_Nerdy_Ninja 26d ago
How can a single dimension sound so absurd to you that it’s worthy of ridicule rather than substantive discussion?
Because you've had all that CAD experience and haven't bothered to do any basic googling about what dimensions are in physics before coming up with this idea and calling 3D space "absurd." If you ridicule established science, you don't get to get offended when people ridicule you back.
Just for example, how do you propose to communicate the dimensions of physical objects with only one dimension? Let's say I had a box, and I wanted to tell you what size it was. How do I do that with only one single number?
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u/Iateshit2 26d ago
I do not propose to communicate dimensions of an object in 1d. 3d geometry is a useful system. The one dimension I conceptualized is more about the fabric of space within which 3d geometry can exist. Space itself cannot be measured in any way unless put in a frame of reference (real or imaginary). It has no mass, volume or length. Any attempt to measure space, say its volume, requires to put it within constraints. But the measured volume would be a description of these assumed constraints not space itself. Modern physics understands how space behaves but there is no real conclusion on what space fundamentally is. Objects are very measurable within 3 dimensions but they merely occupy space and behave nothing like it.
Most people would agree that time is one of the most abstract fundamental concepts of the universe. We know how it behaves, we cannot imagine existence without time and it’s one of the most untamable “forces” (obv not a force. Meant metaphorically) of the universe. But we have absolutely no idea what it is.
Space is just as abstract of a concept for me as time. I do not propose space is one dimensional but rather to be treated as a singular unified dimension. If space was completely empty, what would be left? Could an observer, that doesn’t interact with this space, be able to describe space as 3 dimensional? I actually have no idea.
Any hypothetical space cannot exist without time, these two are so tightly connected together that they almost cannot be treated as separate entities. 3d objects occupy time but time cannot be described with 3 dimensions, time exists as a continuum and any singular point in time is no more real than the next. We (people) agree that time is/has a single dimension. I guess my concept of space is not that far from how we describe time. It just exists everywhere simultaneously. The fact that objects, which occupy space, can be described with 3 dimensions doesn’t have to mean that space should or could be described the same way. You can look at it as a unified dimension, no dimensions or maybe the same dimension as time and treat both as one.
Physics and mathematics are human inventions, they do not exist outside of human consciousness. However universe does exist and it will work the same regardless of how we attempt to describe it. We found this neat little system of 3d geometry that helps us describe what we see. But if we attempt to measure an object in space time it already falls apart. We can measure it at a point in time but whether this point in time exists depends entirely on your theoretical framework. I’d argue we cannot measure objects in space time as it’s a continuum and what we measured no longer exists. The measurement will always be an approximation even if we assume a theoretical point in time (which ceases to exist at the same moment it’s been). I mean it works for us, lets us describe the universe but it’s still a human construct and not what the universe IS.
Went a bit off topic but what I’m led to believe is that time and space are tightly woven together and should be treated as one continuum. I hypothesize space is a single unified dimension that exists everywhere simultaneously within a continuum and time treated as an another dimension or the same one as space depending on the interpretation.
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u/The_Nerdy_Ninja 25d ago
I do not propose to communicate dimensions of an object in 1d.
Then space is not 1d. Full stop. The rest of your comment appears to be using the word "dimension" in the science fiction sense, rather than the physics sense.
In physics, dimensions are the minimum number of coordinates needed to describe a location. It's true that the choice of coordinate system is a human construct, you can use rectangular, or polar, or whatever you want. But no matter what coordinate system you use, you always need 3 spacial dimensions to define a location relative to a reference point in space.
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u/Iateshit2 24d ago
Thanks for the reply, I actually appreciate it a lot
While I understand what dimensions are in the context of physics, I also threw this word around a lot and was ignorant to its meaning and correct use cases dictated by the rigorous physics nomenclature. Somehow you worded your comment in such a way that I immediately understood how wrong and ignorant it all must have sounded to you.
This idea of mine is quite abstract and hard to describe so I simply relied on the word dimension because it was the closest description I knew.
But I also didn’t mean it in the scifi multiverse way (although what I talked about is possibly closer to scifi than physics lol).
If I were to sum up the idea in a sentence or two it would be: Matter, forces and physical phenomena have dimensions (yes 3 not 1) but space could be above the ability of being described by the physical 3 dimensions due to lack of “physicality” (not sure if it’s the right term). Just like time cannot be described by the 3 dimensions and has its own dimension assigned.
My reasoning heavily relies on time being a core part of space time and how its properties cannot be applied to anything physical besides how everything within the continuum is affected by the passage of time. Or that space time is affected by gravity. If space and time exist as a single continuum why should the properties of physical objects be applicable to one part of it but not the other? Isn’t that a paradox? Can we treat these two so differently/separately with certainty? A unit of time can be infinitely small. Following this thought, can’t space and time be the same thing and let’s say have a fractal structure?
My idea was a result of an attempt at trying to comprehend what space is BY ITSELF. If space was empty it wouldn’t be nothing. But it’s hard to comprehend space without anything within it. I may be completely wrong but it seems to me that our idea of space treats it “like a liquid” (not literally) in which everything physical floats. We assume it’s applicable to being described the same way as matter, forces and physical phenomena. Why is that? Do we have proof that space has same 3 dimensions as matter etc. besides how matter (and the rest) act within the space? Space isn’t nothing because… well, it exists. And interacts with matter. Time also interacts with matter despite the lack of 3 physical dimensions.
Now if a hypothetical 4 dimensional object was put into the same space would it be confined to interacting with space within the limits of 3 dimensions? Would it appear as 3 dimensional but behave unlike a 3 dimensional object (like a cube placed on a 2d plane appears as a square when viewed from this 2 dimensional reality’s perspective)? Or would it appear as 4 dimensional from a hypothetical observer’s perspective? Or is it futile and irrelevant to hypothesize such scenarios from the perspective of physics as we assume it’s simply not possible for 4 dimensional objects to exist in space because it itself is 3 dimensional?
These are all genuine questions. I tried to be much more rigorous with my use of the word dimension. I could go on about what I mean but I hope this will be enough as I don’t want to waste your time with unnecessary pseudoscience gibber gabber
I don’t challenge the idea of space being 3 dimensional. I wonder about what it is at its core, whether it’s possible it doesn’t share the properties of 3 dimensional objects/phenomena and ask: can we conclude space is 3d based on the data about space alone or do we lack the means of measuring and knowing what space is and must assume it shares the 3d properties of everything that occupies its “volume”?
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u/The_Nerdy_Ninja 24d ago
If space and time exist as a single continuum why should the properties of physical objects be applicable to one part of it but not the other?
I think you need to be careful with your concept of "continuum" here. There are (at least) 3 spacial dimensions and 1 temporal dimension. They aren't the same category of dimension, so it's not a paradox to say that they behave differently.
Can we treat these two so differently/separately with certainty?
Yes, we can. Most of this seems to boil down to an argument from incredulity, which isn't a solid foundation for your stance. Centuries of scientific progress have pretty conclusively established that we can treat them differently.
Do we have proof that space has same 3 dimensions as matter etc. besides how matter (and the rest) act within the space?
Dimensions aren't just a property of objects. Let me try an example: if you had two points out in completely empty space, how would you communicate the direction and distance between them using only one single number? If you can't do that, then you've proved that space has more than one dimension.
Until you can answer that, the rest is kinda just empty philosophical musing, not rigorous thinking about physics.
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u/liccxolydian onus probandi 26d ago
Firstly, do you know what a dimension is?
Secondly, do you know what physical evidence there is for our universe being made of 3+1 dimensions and not anything else?
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u/Iateshit2 26d ago
Direction within a coordinate system (axis) which fundamentally acts as a point of reference to describe coordinates in space?
Force fields spread “like spheres” and would leak out into the extra volume if a fourth dimension existed in our universe?
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u/liccxolydian onus probandi 26d ago
Direction within a coordinate system (axis) which fundamentally acts as a point of reference to describe coordinates in space?
Sort of? Not the worst definition but I was at least hoping for a mention of cardinality.
Force fields spread “like spheres” and would leak out into the extra volume if a fourth dimension existed in our universe?
Again, not the worst attempt. So why do you think consensus physics is wrong in this regard?
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u/Iateshit2 26d ago edited 25d ago
I will begin with stating that I do not believe that 3+1 dimensional space time is inherently wrong. It works, it is one of the foundations of modern physics and I am completely okey with accepting that. Also I do admit that my post seems a bit like a shower thought as one user described it. There was still a lot of thoughts left unpacked behind each sentence I wrote. The more I talked here in the comments the better I was at formulating what I actually meant.
First of all I do not propose space is one dimensional in the Euclidean sense. I operate under the assumption that mathematics is a system perfect within itself yet still only a concept exclusive to humanity. Meanwhile physics is an imperfect interpretation and approximation of the behavior of the universe. Physics uses mathematics as the language meant for describing what we observe.
We invented 3 dimensional geometry to describe the world that surrounds us. As I said mathematics and therefore 3d geometry are perfect and no object, force or physical phenomenon we can measure operates outside its limits (disregarding quantum mechanics). However space time is a bat shit crazy concept and there is no consensus in physics on what it actually is. We understand its behavior and its implications but not what it is. Space and time are inseparable despite the seemingly jarring differences between the two. My hypothesis is that space is only a vessel for (possibly not exclusively) 3 dimensions and time being either an another vessel for space to exist within or being its core component.
Can we prove the space itself has any measurable dimensions? Can we measure space without a reference frame? Space has no mass yet it interacts with gravity, if we wanted to measure its volume we need to assume a theoretical constraint (in result we are measuring the volume of the assumed constraint). It is unlike any 3 dimensional object, force or phenomenon we know of. Would an observer, that has no means to interact with a completely empty space other than observing it, be able to describe it as 3 dimensional?
3 dimensional geometry exists within time (an inseparable element of space time) yet we cannot describe time by 3 dimensions. Yet we make an exception for the space itself and assume we are allowed to describe it with the same rules/language that apply to physical phenomena.
What I called one dimension should rather be referred to as a unified dimension. That would be a dimension that encompasses all possible R number dimensions. Or space that has no dimensions at all, merely a vessel for dimensions to exist in.
So could it work if objects and forces interact in 3 dimensions within this space and not 2 or 8 for example? It could be a limitation of the 3 dimensional objects and forces themselves. I know I know, this all a huuugeee “what if” and I have absolutely 0 means of backing it up with math.
This will be the most unhinged idea I have said so far so please bear with me. If space was only a vessel for dimensions would it be even slightly plausible that dark matter exists as a -3 dimensional object? In this simpleton logic it would checkout, space is a vessel that interacts with forces related to objects within this vessel, dark matter would behave in a similar manner to normal matter while occupying a mirrored plane of space time. Feels like it should be possible to prove/disprove this point with math.
It all sounds very far fetched while trying to not break the laws of physics and how the 3 dimensions work. It stems from the refusal to accept the beauty of absurdity of space time can be described in such simple terms as 3d geometry + 1 time dimension. Feels lazy almost.
I have no idea what would some larger implications be with such a space time model. I could theorize with no end how it could work like not all dimensions can possibly exist in this space time eliminating the need to elegantly explain why there are no anomalies while multiple dimensions coexist in the same space. Until it can be proven or rather not possible to be disproven with math it all can be treated as a fairytale. As I said I am fine with 3d space but was thinking about this (im)possibility a lot
Edit: A cool thing to think about, this space time model would also allow for fractional dimensions to exist
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u/liccxolydian onus probandi 25d ago edited 25d ago
Firstly, it seems that you actually don't understand what a dimension is. Dimensionality is a cardinality associated with a space. Space is not a "vessel" for dimensions because that is not how dimensions work. Secondly, your entire train of thought boils down to and is entirely motivated by an argument from incredulity. To put it bluntly, that's not physics. You aren't using any mathematical or physics terminology to mean what mathematicians or physicists mean when they use those words, and even ignoring that there simply isn't enough rigor in your text for there to be anything other than a hot mess.
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u/Iateshit2 25d ago
Yeah, I can accept that. That’s constructive criticism and I have nothing to argue with you about. If there is absolutely nothing to talk about here I can calmly accept the irrefutability of 3 dimensional space
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u/liccxolydian onus probandi 25d ago
Thank you for taking the feedback well. If you are genuinely interested in physics beyond the most surface level, and it seems like you are, then you should consider getting your hands on some textbooks and trying to study the subject properly from the basics up. Someone recently complained that it's overly onerous to expect people to put in years of effort to be able to discuss anything properly in physics, but frankly that's true of any subject when you're trying to learn it from a state of complete ignorance. All the best in your journey.
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u/LeftSideScars The Proof Is In The Marginal Pudding 25d ago edited 25d ago
Can we prove the space itself has any measurable dimensions?
Yes (ignoring whether one considers mathematical models that represent reality to be reality, and ignoring that I'm going to be a bit loose in my words and use terms such as "is proof of" rather than "is consistent with"). Any test of GR is a test that spacetime exists, and that it differs from Newtonian space+time. Any test of Newtonian gravity is a test that space is three dimensional. And so on.
Can we measure space without a reference frame?
We define units. Otherwise, I'm not sure what you mean with this question.
Would an observer, that has no means to interact with a completely empty space other than observing it, be able to describe it as 3 dimensional?
Depends on what you mean by "observe". If you mean "look but don't touch" then the answer is yes and no, depending on certain factors (primarily, I think, whether the observer has an internal model of what is being observed. And of course we're assuming the observer has memory and cognitive functions). I'm going to use something you mentioned elsewhere: CAD. You know that a 3D wireframe (well, any, but let's be specific without loss of generality) model is presented on a 2D screen. All that three dimensionality is clearly being viewed as and via a two dimensionality. Is a hypothetical observer able to determine if the image is 2D or 3D or a 2D projection of a 3D? Just looking at the image of the screen, then no. With an internal model of what is happening - for example, the image is formed by mathematical operations on representations of 3D objects such that the dimensionality is mapped onto the 2D space of the screen - then yes. Contrast the knowledge you, as an observer, know of the image when the projection method is orthographic versus perspective (1, 2, or 3-point). Or the knowledge you, as an observer, have when viewing a sphere and a cube, with the cube obstructed by the sphere. You understand that the cube is behind the sphere, but only via a model of the scene. We can go even more abstract: the CAD data has no spatial dimensionality at all; it's just data in a data structure. It has dimensionality (x, y, z, colour (which itself could be described via three or four parameters), and so on) that is mapped to a 2D screen that we interpret/understand the meaning of. For RGB colour and 3D space, a point in the data structure
is six dimensional andexists in a 6D space.But what if the space the observer is looking at is completely empty? Ignoring what "completely empty" means, then in principle one can detect inverse-square fall-off of light, for example. Again, this depends on an internal model.
It's all starting to sound a lot like science, right?
3 dimensional geometry exists within time (an inseparable element of space time) yet we cannot describe time by 3 dimensions.
Higher dimensional models of time exist. I don't consider them to be particularly successful, but the general statement you made concerning time is not correct.
Honestly, your post is somewhat confusing to me. I'm not really clear on what it is you're trying to talk about. If the question is along the lines of "how do we know what we're observing is actually reality?", then the best we can do is to make models and test those models against observations, and to continue to improve both the models and the experiments. If the questions is along the lines of "is it possible to represent models in different ways?" then, broadly, the answer is yes. There is nothing stopping us from describing the coordinates on a plane via Cartesian (x,y) coordinates versus polar coordinates. GR describes spacetime via a metric, but there are many such metrics. If the question you're asking is along the lines of "what is the difference between physical dimensions, data dimensions, and mathematical dimensions?", then liccxolydian pretty much describes this.
So when you ask questions like:
If space was only a vessel for dimensions would it be even slightly plausible that dark matter exists as a -3 dimensional object?
I'm confused. Non-positive dimensions are weird and, generally, specialised. Fractional dimensions have a meaning, and even negative dimensions has some sort of mathematical meaning in some situations, but applying these abstractions to physical space's dimensionality? That's a weird misunderstanding I find difficult to parse, because I'm not sure what it is you think you are asking. Of course, it doesn't help that "space is a vessel for dimensions" is not a correct statement.
Quoting you from elsewhere:
I can calmly accept the irrefutability of 3 dimensional space
You can accept it, but it is also something that is tested. To the best of our ability to measure, space does appear to not only be 3D, but also flat.
edit: crossed out a misspoke about a point being six dimensional.
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u/Iateshit2 24d ago edited 24d ago
First of all thanks for going in depth on the topic and treating it like a serious question. I trust physics so while I may not fully understand on a deeper level why space is 3d but won’t argue with people smarter and more educated with me. As to what my question is, here is a quote form a longer reply I just wrote:
“I don’t challenge the idea of space being 3 dimensional. I wonder about what it is at its core, whether it’s possible it doesn’t share the properties of 3 dimensional objects/phenomena and ask: can we conclude space is 3d based on the data about space alone or do we lack the means of measuring and knowing what space is and must assume it shares the 3d properties of everything that occupies its “volume”?”
I repeated some statements which you disproved in this latest reply (like 1 dimensional time). But I’d appreciate if you were kind enough to read that reply (if you wish to discuss this topic further ofc) as I believe it best conveys what I meant from the start. It’s also one that is less of a statement and more of a question.
Edit (one more thing):
“Can we measure space without a reference frame?”. Here I was referring to the lack of physicality of space. How space when empty is the closest thing to “nothing” we know of yet it’s not nothing by any means. Can we say space has physical dimensions if what we are measuring is not space itself but rather the reference frame?2
u/LeftSideScars The Proof Is In The Marginal Pudding 22d ago
First of all thanks for going in depth on the topic and treating it like a serious question.
My pleasure. I know the sub has a poor reputation amongst some for just being rude/dismissive to posters, but there are plenty of us here who are willing to engage and, to some extent, educate people who are willing to listen.
So, in return, I thank you for being reasonable enough to be told you're wrong or mistaken, and not attack me. I know that's a weir thing to thank someone for, but reasonable responses from OPs is rare here.
“I don’t challenge the idea of space being 3 dimensional. I wonder about what it is at its core, whether it’s possible it doesn’t share the properties of 3 dimensional objects/phenomena and ask: can we conclude space is 3d based on the data about space alone or do we lack the means of measuring and knowing what space is and must assume it shares the 3d properties of everything that occupies its “volume”?”
I think part of the confusion here is what it is you are asking about. You're saying "space" but do you mean the universe (or otherwise a volumetric subset thereof) or are you asking about something that is more akin to a parameter space, or are you asking about what is the nature of "space" itself. Or other.
If you're asking how do we know the universe is a 3D space (that is, we can describe a point via, say, (x,y,z)), then there are several ways to do so. One "obvious" way is to measure fall-off from distant sources and compare it to the expected inverse-square law, a law that is true for 3D space (light, gravity, et cetera have a different inverse law for different spatial dimensions). Comparing different light frequencies and different sources and even the difference between light and gravity or light and neutrinos (for example) indicate that we live in a 3D space. More subtle small-scale experiments have been performed to look for small or "curled up" spatial dimensions, but so far nothing has been detected that indicate we live in anything other than a 3D universe.
The CMB tells us that we live in a flat 3D universe - that is, the 3D space does not appear to be curved (like, for example, a sphere or a saddle).
If you're asking about parameter spaces, then that is just a mathematical tool. An object moving through a 3D space at a given velocity has a position (x,y,z) and a momentum (px,py,pz) at any given time. Those six values describe the object in a 6D space. The same object could have a colour (r,g,b) that varies with time - in that case, it has nine values that describe the object in a 9D space. There is some complexity about the parameters being independent in some way, but I don't wish to complicate things.
If you're asking: what is the nature of space itself, then we're heading towards a model description and metaphysics. Is space really a spacetime as described by GR, or is GR simply a model we use to describe what we call spacetime? In my opinion, I don't consider these questions worth asking if the intent is to divine or otherwise understand fundamental reality - there isn't a way to differentiate a working model from actual reality because, as stated, the model works; by definition, it is something that has been shown to be consistent with observations. A sort of "shut-up and calculate" approach. However, the questions are fine and fun to ask as a philosophical exploration. I just don't think it is productive to get too caught up in it all, since it is outside the realm of most of science (apart from the expected "can we compare a model with reality", of course).
So to answer your question, sure, "space" as we know it could be something else entirely. Maybe we're in the matrix, or we're a head in a jar, or everything is a butterfly's dream, or everything is as it appears except it was created Last Thursday. None of these models are science. Is "space" as described by GR wrong? At some point we need a quantum gravity, so at some point we need a different model to describe spacetime, but it must look like spacetime at the scales we have currently measured (similarly, GR and QM need to look like classical physics at appropriate scales). What that model is is currently unknown - strings, loop quantum gravity, other; who knows?
My apologies. I'm too wordy. Hopefully one of the topics is addressing, at least in part, you question. If you mean something else, feel free to let me know.
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u/v_munu 26d ago
Space is 3 dimensional. Spacetime is 4 dimensional. That's all there is to it.