>>9554172If the universe has positive (spherical) curvature, then travel in a straight line (a geodesic, which is the straightest possible, the shortest track between two points) will bring you back to your starting point.
The "surface of the Earth" is only a two dimensional analogy. We can see it's curved into a 3rd dimension, but that's INTRINSIC curvature. The circle-painting trick works. If a paper sheet is curled into a cylinder, that EXTRINSIC curvature. The Greeks couldn't have discovered it with triangles. INTRINSIC curvature requires tearing or overlapping sections of paper. Which is why all flat maps of Earth inevitably have distortion.
If you want to consider our 3-space to be curved within a 4th spatial dimension, feel free to do so. But be aware that doesn't necessarily mean the 4th dimension exists. In the globe-model, the surface is all there is. There's no "inside".
To really understand, takes non-Euclidian geometry (which I am not an expert in) but I hope I answered your question.
