## Things To Be Thankful For

A couple buildings around town have blackboard paint and a writing prompt on the walls. Here’s one my love and I wandered across the other day while going to Fabiano’s Chocolate for the obvious reason. (The reason was to see their novelty three-foot-tall, 75-pound solid chocolate bunny. Also to buy less huge piles of candy.)

I recognized that mathematics majors had been past. Well, anyone with an interest in popular mathematics might have written they’re grateful for “G. Cantor”. His work’s escaped into the popular imagination, at least a bit. “C. Weirstrauβ”, though, that’s a mathematics major at work.

Karl Weierstrass, the way his name’s rendered in the English-language mathematics books I know, was one of the people who made analysis what it is today. Analysis is, at heart, the study of why calculus works. He attacked the foundations of calculus, which by modern standards weren’t quite rigorous. And he did brilliantly, giving us the modern standards of rigor. He’s terrified generations of mathematics majors by defining what it is for a function to be continuous. Roughly, it means we can draw the graph of a function without having to lift a pencil. He put it in a non-rough manner. He also developed the precise modern idea for what a limit is. Roughly, a limit is exactly what you might think it means; but to be precise takes genius.

Among Weierstrass’s students was Georg Cantor. His is a more familiar name. He proved that just because a set has infinitely many elements in it doesn’t mean that it can’t be quite small compared to other infinitely large sets. His Diagonal Argument shows there must be, in a sense, more real numbers than there are counting numbers. And a child can understand it. Cantor also pioneered the modern idea of set theory. For a while this looked like it might be the best way to understand why arithmetic works like it does. (My understanding is it’s now thought category theory more fundamental. But I don’t know category theory well enough to have an informed opinion.)

The person grateful to Michigan State University basketball I assume wrote that before last Sunday, when the school wrecked so many NCAA tournament brackets.

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