A crochet model of a hyperbolic plane is simple to make, and fascinating to play with. With these models, learning about hyperbolic geometry becomes kinesthetically available.
Until recently, some mathematicians thought that hyperbolic geometry was purely theoretical and could not be effectively modeled in the real world. Here is one I finished recently.
Click the “Continue reading” link to learn why hyperbolic planes are cool, access some links, see how I made one, and enjoy a gallery of hyperbolic planes which I have crocheted.