• TheLeadenSea@sh.itjust.works
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    1 day ago

    Straight lines. Also two sets of parallel lines. This is one definition of a square, but not the common one.

    • Snazz@lemmy.world
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      5 hours ago

      This shape could exist as a projection onto an upright cylinder, wrapping around the cylinder. The two straight edges go vertically along opposite sides of the cylinder. The curved lines wrap around the circumference. The lines are now straight and parallel on the net of the cylinder.

      But we can go further: Imagine taking this cylinder and extending it. Wrap it into a loop by connecting the top to the bottom so it forms a torus (doughnut) shape. This connects both sides of the shape, now all “interior” angles are on the inside of the square, and all “exterior” angles are on the outside. The inside and outside just happen to be the same side.

    • mcqtom@lemmy.world
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      24 hours ago

      I believe these lines are straight with a black hole at the centre.

      • Zkuld@lemmy.world
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        15 hours ago

        I would guess on a sphere these can be straight yes: The pole goes into the center of cicular thing and radius of the sphere needs to put the other arc on one latitude.

      • NateNate60@lemmy.world
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        20 hours ago

        Euclid’s first postulate: Give two points, there exists exactly one straight line that includes both of them.