Books about non-euclidean geometry I study physics and want to know the best books to learn non-euclidean geometry in an easy way.
Book covering differential geometry and topology for physics I'm interested in learning how to use geometry and topology in physics. Could anyone recommend a book that covers these topics, preferably with some proofs, physical applications, and emphasis on geometrical intuition? I've taken an introductory course in real analysis but no other higher math.
Technique for finding the centerline of a curved object? I'm curious to know if anyone knows of any effective techniques for finding the center line of a curved object.  In the screenshot below you'll see a crude version of what I mean.     Is there any way to get that line to perfectly trace the center, or is it easiest to just eyeball it?  Photoshop or Illustrator techniques are acceptable.