Just another silly question that may deserve a wise answer.

  • it's more of a science question? – user35983 Feb 20 '19 at 17:50
  • This might be best in the Physics SE. – Frank Hubeny Feb 20 '19 at 17:54
  • 1
    @FrankHubeny I don't think they would like it either – John Dvorak Feb 20 '19 at 18:06
  • @JohnDvorak I don't think they would either, so I attempted an answer. – Frank Hubeny Feb 20 '19 at 18:10

According to Wikipedia a flat universe would have this property:

Zero curvature (flat); a drawn triangle's angles add up to 180° and the Pythagorean theorem holds...

This is not the case for the round Earth which has positive curvature on its surface:

Positive curvature; a drawn triangle's angles add up to more than 180°...

The spherical objects in the universe may make it appear bumpy from a local perspective. From a more global perspective one would view the universe as flat having zero curvature even though those spherical objects within the universe have positive curvature.

"Shape of the universe" Wikipedia https://en.wikipedia.org/wiki/Shape_of_the_universe

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Here's a similar question: if this sheet of paper is flat, can the circle drawn on it be round? And the answer is yes. Of course.

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Flatness or non-flatness of the universe is an issue concerning the large scale structure of the universe, more precisely a question about the curvature of spacetime.

Roundness of the earth and of other cosmic bodies is a local phenomenon due to the gravity of rotating bodies.

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