The Nature of Parallelism

The Nature of Parallelism

Available on Prime Video, The Great Courses Signature Collection
S1 E7: Examine how our usual definition of parallelism is impossible to check. Use the fundamental assumptions you've learned to follow in Euclid's footsteps and create an alternative way of checking if lines are parallel. See how, using this result, it's possible to compute the circumference of the Earth just by using shadows!