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Yesterday I had to explain to a non-math undergraduate student what Riemannian geometry is. Surprisingly difficult. I tried to explain curvature in pictures and mentioned as an example that you can't make an accurate map of any region of Earth on a flat sheet of paper because the former is not flat but the latter is. I wonder what examples people use in similar situations.

@herid for me it’s the you can’t flatten a cut from the peel of an apple or the equator to pole to equator thing that clearly shows Euclidian geometry is simply not correct on a sphere in relation to the internal angles of a triangle. For me the great shocker is in explaining that the dot product misses the assumption made about the metric tensor in flat spaces like we use at school. #math

@herid

I don't know, but when you come up with one let me know because I need a babyfood example to understand it myself.

(Apparently Einstein had to consult with one of his mathematician buddies to explain it to him so he could complete his work on General Relativity.)

@herid IMO the map is a nice example which can also be used to illustrate that the surface of a cylinder is *not* curved in this sense. An example that, IMO, is great to add, as it emphasises that "curvature" in Riemannian geometry is something subtly different from the "everyday concept" of curved.

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