I'm not a topological expert, but I'm pretty sure you can have a surface without... | Hacker News

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kelseyfrog 6 months ago | parent | context | favorite | on: Thought experiments that fray the fabric of space-...

I'm not a topological expert, but I'm pretty sure you can have a surface without an interior. A unit sphere would be a good example of a surface without an interior.

bongodongobob 6 months ago [–]

? It by definition has a radius of 1.

krukah 6 months ago | [–]

unit sphere != unit ball

The former is the boundary, the latter is the interior + boundary. One of the great arbitrary naming conventions of math.

magicalhippo 6 months ago | | [–]

Minor nitpick, the ball might be closed or open, depending on whether the boundary is included or not, respectively.

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