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knowwhatyoudontknow

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- TL;DR Summary
- 3-spheres in the context of curvature.

A 1-sphere exists in 2D space. It is a circle in flat space.

A 2-sphere is a 1-sphere embedded in 3D space. Its surface is non flat and 2 dimensional.

A 3-sphere is a 2-sphere embedded in 4D space. Its surface is non flat and 3 dimensional.

What does this last sentence mean in layman's terms? What is the physical meaning of the 4th dimension? Also, can the 2 and 3-spheres be defined in terms of flat space?

A 2-sphere is a 1-sphere embedded in 3D space. Its surface is non flat and 2 dimensional.

A 3-sphere is a 2-sphere embedded in 4D space. Its surface is non flat and 3 dimensional.

What does this last sentence mean in layman's terms? What is the physical meaning of the 4th dimension? Also, can the 2 and 3-spheres be defined in terms of flat space?