Is Our Universe Euclidean or Non-Euclidean?

For the record, I am on the fence whether the universe is flat or curved (or the shape of a torus, sphere, etc.), but just like how we have discovered that the earth is not flat, it got me wondering and others questioning the familiar geometry that we know and love — Euclidean or “flat” geometry, in terms of applying it to the shape of the universe. Derived from Euclid’s The Elements, Euclidean geometry starts off with five basic axioms and postulates. It is also known as “plane” geometry, since this type of geometry only deals with flat surfaces or planes (zero curvature). The angles in a triangle always add up to 180°, or for a quadrilateral 360°, and so on (there is a formula for this). The shortest distance between two points is a straight line, not a curved line or arc. More importantly, parallel lines remain parallel. However, the reason non-Euclidean geometry came into fruition was because of the ambiguity of Euclid’s fifth postulate. <a href="https://mathconduit.medium.com/is-our-universe-euclidean-or-non-euclidean-417b22cdf29f">Read More</a>