How is the 3-d space an approximation of Euclidean Geometry?

Click For Summary

Discussion Overview

The discussion revolves around the nature of 3-dimensional space as an approximation of Euclidean geometry, exploring the experimental observations and logical reasoning that support this idea. Participants examine the implications of curvature in the universe and its effects on geometric properties, particularly in relation to triangles and parallel lines.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant inquires about the experimental observations or logic that demonstrate 3D space as an approximation of Euclidean geometry, questioning the role of parallel lines and the behavior of light.
  • Another participant suggests that the sum of triangle angles being 180 degrees indicates flat geometry, referencing external resources for further information.
  • A participant acknowledges that light behavior is used to measure the universe's geometry and questions whether the curvature of the universe affects the sum of triangle angles drawn on paper.
  • There is a discussion about whether local approximations are always flat, with one participant asserting that they are, similar to how the Earth's surface appears flat locally.
  • Another participant challenges the assertion of local flatness, asking if it holds true in a universe with significantly higher curvature.
  • A later reply states that the universe is sufficiently large for it to appear flat locally and mentions the inability to detect curvature in the largest observable patches.

Areas of Agreement / Disagreement

Participants express differing views on the nature of local flatness and its implications for geometry in a curved universe. The discussion remains unresolved regarding the conditions under which local approximations can be considered flat.

Contextual Notes

Participants express uncertainty regarding the assumptions about curvature and local flatness, and the implications of these concepts for understanding geometry in different contexts.

ask_LXXXVI
Messages
53
Reaction score
0
I would like to know the basic experimental observations or the logic which prove that the 3-d space which we inhabit is a close approximation of Euclidean Geometry. is it because parallel lines don't appear to converge or diverge? But how is this established, as we can't draw perfect straight lines. Do we observe behavior of parallel rays of light in vacuum or something similar. I am not concerned about the 4-d space-time . Just the good ol' 3-d space . :smile: .
I am a beginner so it would be good if you direct me to websites where related info is given .
 
Space news on Phys.org
Triangle angles don't sum up to 180 deg if geometry isn't flat. But I think that best evidence comes from here: http://map.gsfc.nasa.gov/mission/sgoals_parameters_geom.html"
 
Last edited by a moderator:
Ok , I can appreciate that the behaviour of light is used to measure the geometry of the universe.

Is it because of the curvature of our universe that the triangles which we draw on paper have angles which sum up to ~180 degree ?

Had our universe been of, let's say , elliptical curvature would angles of triangles drawn on paper sum to less than 180 degrees ?

Or is the curvature simply a measure of the way light travels through free space?
 
ask_LXXXVI said:
Is it because of the curvature of our universe that the triangles which we draw on paper have angles which sum up to ~180 degree ?

No, it is because local approximation is always flat, just as surface of Earth appears flat to us.
 
Calimero said:
No, it is because local approximation is always flat, just as surface of Earth appears flat to us.

How is it "always" flat ?

Would the local approximation be flat even in a universe with much high curvature than ours ?(I am assuming a hypothetical universe just for sake of understanding).

Or were you implying our particular situation?
 
Well, we obviously live in sufficiently large universe that locally it appears flat to us. Now we know even more. We know that we can't detect any curvature even if look at the largest possible observable patch.
 
okay.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 9 ·
Replies
9
Views
5K
  • · Replies 25 ·
Replies
25
Views
4K
  • · Replies 29 ·
Replies
29
Views
8K
  • · Replies 8 ·
Replies
8
Views
4K