Is Our Universe Really Flat or is it Just Euclidean Jargon?

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SUMMARY

The discussion clarifies the scientific terminology surrounding the shape of the universe, specifically the concept of "flat" as it relates to higher dimensions. Scientists refer to a flat universe as "asymptotically Euclidean," indicating a lack of intrinsic curvature, akin to a rectilinear grid in Cartesian geometry. This means that in such a universe, the interior angles of triangles would sum to 180 degrees, which is often misunderstood as implying a two-dimensional space. The term "flat" is jargon that specifically denotes the absence of curvature rather than dimensionality.

PREREQUISITES
  • Understanding of higher-dimensional space-time concepts
  • Familiarity with Euclidean geometry
  • Knowledge of intrinsic curvature in cosmology
  • Basic grasp of scientific terminology in physics
NEXT STEPS
  • Research the concept of asymptotic flatness in cosmology
  • Explore the implications of intrinsic curvature in the universe
  • Study the differences between Euclidean and non-Euclidean geometries
  • Review the Cosmology FAQ for common misconceptions
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This discussion is beneficial for physicists, cosmologists, and students of astronomy who seek to understand the complexities of the universe's shape and the terminology used in scientific discourse.

mtv22
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I read that most scientists believe that the Universe is either infinitely flat or pringle-shaped flat, and that doesn't make sense with me. I don't understand how our 3 dimensional world could be a part of a 2 dimensional universe.
 
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Hi mtv22, welcome to physics forums!
That's not what is meant by 'flat'---they're using the term to describe higher dimensions (namely 3+1 space-time).

For the http://en.wikipedia.org/wiki/Shape_of_the_universe" flat means asymptotically euclidean. Instead of having intrinsic curvature, the universe would be a perfectly flat, rectilinear grid (like you use in Cartesian geometry), where the interior angles of triangles add to 180 degrees, etc etc.
 
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A lot of people ask this, and it's confusing because it's not always made clear that the term "flat" is jargon for "Euclidean." Granted, they call it flat because it implies the absence of "curvature", but the term curvature itself is something that has a very specific definition. Either way, it does not mean two-dimensional! We should probably add something about this to the Cosmology FAQ.
 

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