An excellent read to celebrate π day :-) The story of how the mathematics of general relativity were put together is one of the well documented insights into h

An excellent read to celebrate π day :-) The story of how the mathematics of general relativity were put together is one of the well documented insights into how the human intellect incrementally tackles understanding reality around us. Physical intuition (here represented by Einstein) and mathematical structure (embodied in Grossmann) dance around before (occasionally) landing into a magical place that somehow turns out to be "true". Neither intuition about how nature works nor mathematical skill are sufficient conditions for this to happen. If you read to the end you'll learn briefly about "teleparallel" attempts at gravity/electromagnetism unification - which is just one of the many failed subsequent attempts of Einstein to extend his intuition one further step. Something that is not covered in much detail is how much Grossmann knew of and appreciated Riemann's work and thinking. Decades prior, Riemann already thought that the geometry of (three)-space is something to be determined experimentally.