[User23]

No mention of Hermann Minkowski[1]? As any educated mathematician knows, it was Gauss's student Riemann who solved the maths for n-dimensional manifolds, but it was Minkowski who developed modern spacetime.

[1] https://en.wikipedia.org/wiki/Hermann_Minkowski

[debatem1]

Minkowski blew my mind when I fist started to understand his work. Without a doubt the most useful pieces of math I learned after multiplication, and more intuitive even than that.

[gjm11]

What work in particular? Minkowski did a lot of neat things. (But I'm not sure I'd describe any of the ones I know of as more intuitive than multiplication.)

[debatem1]

His work on the geometry of numbers. It was like a secret decoder ring for the language of higher math at the time, while being both elegant and tangible. Compare to multiplication, which occasionally still bears strangely shaped fruit for me even today.