Question about Space -- Is Space itself a 4th dimensional object?

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Discussion Overview

The discussion revolves around the nature of space and its dimensionality, particularly whether space itself can be considered a fourth-dimensional object. Participants explore concepts related to special relativity, the expansion of the universe, and the relationship between spatial dimensions and time.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions if space can be considered a fourth-dimensional object, suggesting it is not nothing since it is expanding.
  • Another participant asserts that the local topology of the universe is three-dimensional, indicating that spacetime has three spatial dimensions.
  • A different participant challenges the notion of space expanding, arguing that it is more accurate to say the distance between distant objects is expanding.
  • One participant describes the dimensional hierarchy, stating that time is the fourth dimension and discussing how this relates to concepts like tesseracts and string theory.
  • Another participant notes that string theory is not widely accepted due to a lack of evidence compared to general relativity, which has substantial observational support.

Areas of Agreement / Disagreement

Participants express differing views on the dimensionality of space and the implications of its expansion. There is no consensus on whether space can be classified as a fourth-dimensional object, and the discussion includes competing theories and interpretations.

Contextual Notes

Some claims rely on specific definitions of dimensions and the nature of spacetime, which may not be universally accepted. The relationship between general relativity and string theory remains unresolved, with participants highlighting the lack of evidence for string theory compared to general relativity.

SaniT404
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Ok, so I was just in physics class today and we were talking about special relativity... anyways, the instructor referred to how the universe is expanding, and so much so that there are places we could never ever get to because it's expanding fasterling than the speed of light. Anyways, this got me thinking about Space itself and I was wondering. Is Space in of itself a 4th dimensional object? Because clearly it can't be NOTHING if it is expanding... right? It's just intangible to us... so couldn't it just be a really big object perpendicular to the 3d matter on/in/around it?
 
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The local topology of our universe is 3-dimensional so spacetime also has 3 spatial dimensions.
 
SaniT404 said:
the instructor referred to how the universe is expanding, and so much so that there are places we could never ever get to because it's expanding fasterling than the speed of light.
This is not quite correct. See:



SaniT404 said:
Is Space in of itself a 4th dimensional object?
Space-time is 4D, space is 3D

SaniT404 said:
Because clearly it can't be NOTHING if it is expanding... right?
See this similar question:
https://www.physicsforums.com/threads/on-space-time.783833/
 
Space is 3D where we have (x,y,z), then we add the third component, time or t, then we have (t,x,y,z) a 4D; which is why we call it Space-time. This t is most affected by massive objects such as black holes which not only bent space but also time.
 
SaniT404 said:
Is Space in of itself a 4th dimensional object? Because clearly it can't be NOTHING if it is expanding... right?
No, space is not a thing. The expression 'space is expanding' is a misnomer. It is more accurate to say the distance between distant objects is expanding.
 
So what I'm getting... that time is the 4th dimension, which is what I always thought. But then I saw several other places that changed the way I saw it. The first dimension would be considered a line. 2nd dimension is a square, which is simply a shape perpendicular to the 1st dimension. We can all agree with that as well, yes? So the third dimension is perpendicular to a square, or the second dimension. So the fourth dimension must be perpendicular to the third. That's where the tesseract come from. A 4d cube. If I'm correct, this is what the string theory operates on, 11 dimensions, all perpendicular to the dimension before it. So how then is time the 4th dimension... these 2 theories, einstein's and the string theory seem to conflict...
 
Those dimensions are all spatial dimensions, and some of the string theory ones are very weird indeed. String theory is not an accepted mainstream theory (meaning that there's not enough evidence to use it over competing theories) at this time, so even though string theory and GR conflict, we don't have a problem. GR has plenty of observational evidence to support it over competing theories. String theory has little if any.
 
Drakkith said:
Those dimensions are all spatial dimensions, and some of the string theory ones are very weird indeed. String theory is not an accepted mainstream theory (meaning that there's not enough evidence to use it over competing theories) at this time, so even though string theory and GR conflict, we don't have a problem. GR has plenty of observational evidence to support it over competing theories. String theory has little if any.
Ok, thanks, that helps a lot!
 

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