Some people have asked about #PiDay, so here are some thoughts (warning: long-ish thread).
The number π ≈ 3.14, that is, the ratio of circumference to diameter of any circle, has continually captivated mankind since at least the ancient Babylonians four millennia ago.
Indeed, one may reasonably regard the entire Langlands program as an outgrowth of the recognition that Fourier analysis provides ready access to subtle number-theoretical information, much of which to this day we can hardly comprehend in any other way. Miraculous is right.