- #1
ddjj77
- 64
- 4
It's been said that the universe is flat. How can it be flat if flatness has no volume?
Is the Universe Flat Without Volume?
Click For Summary
Discussion Overview
The discussion revolves around the concept of the universe being "flat" and the implications of this term in relation to volume and dimensionality. Participants explore the meaning of "flat" in cosmological terms versus everyday language, and how this affects the understanding of the universe's geometry.
Discussion Character
- Conceptual clarification
- Debate/contested
Main Points Raised
- Some participants question how the universe can be flat if flatness implies no volume.
- Others clarify that "flat" refers to a three-dimensional Euclidean space, despite the lack of volume in the term itself.
- One participant suggests that "2-dimensional" might be a more accurate description, questioning the terminology used to describe shapes without thickness.
- Another participant notes that diagrams often represent the universe in two dimensions for illustrative purposes, which may lead to misunderstandings about its true dimensionality.
- There is a mention of Lawrence Krauss's explanation regarding the terms "open," "closed," and "flat" in cosmology, indicating a potential source for further clarification.
- Some participants express confusion over the distinction between the cosmological meaning of "flat" and its everyday usage, highlighting a conceptual hurdle.
Areas of Agreement / Disagreement
Participants generally agree that the terminology surrounding the concept of "flat" in cosmology is complex and can lead to misunderstandings. However, there is no consensus on the most accurate way to describe the universe's geometry, and multiple competing views remain regarding the implications of flatness.
Contextual Notes
The discussion reflects limitations in understanding the dimensionality of the universe and the terminology used in cosmology, which may depend on specific definitions and interpretations.
- #2
- 29,616
- 21,426
ddjj77 said:
"Flat" means three-dimensional Euclidean.
http://curious.astro.cornell.edu/ab...ow-can-the-universe-be-flat-we-re-3d-beginner
- #3
ddjj77
- 64
- 4
Maybe "flat" isn't the right term; 2-dimensional would be more accurate (see attached image). What would you call a shape with no thickness? Volumeless?
- #4
- 29,616
- 21,426
ddjj77 said:
Those are 2D surfaces. The reason that a lot of diagrams use 2D to represent the universe is that, although you could represent the "flat" universe as a 3D box, you can't draw a curved 3D surface (you'd need 4D for that, which we don't have).
So, these diagrams lose a dimension in order to illustrate the concept of curved space.
It's interesting that you've taken the concept of "flat" so literally.
- #5
- 29,616
- 21,426
PS Lawrence Krauss explains this right at the start of his lecture here:
- #6
ddjj77
- 64
- 4
I thought flat was flat.
Krauss said "..it's open, closed, or flat."
Krauss said "..it's open, closed, or flat."
- #7
- 29,616
- 21,426
ddjj77 said:
No, "flat" in cosmology means 3D but not curved. "Flat" in everyday speech means 2D.
That is an intellectual hurdle you are going to have to jump.
- #8
davenn
Science Advisor
Gold Member
- 9,724
- 11,804
PeroK said:
thanks for that video
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