My lip-bump had a name: *pyogenic granuloma*. You can Google that if you enjoy gross photos. Speaking of annoyances, what about those mathematical cranks, eh?

Back in 2006, I reported that R.S.J. Reddy sent me a copy of his book in which he failed to prove that π is approximately equal to 3.146446. Alert reader Nathan Tenny suggested that I read Underwood Dudley's book *Mathematical Cranks*, It took me a while to get ahold of the book. (I kept hoping to check it out from the U.C. Berkeley library system. Lately, the Math library has been closed on weekends. Which might show something about the intersection between the set of Mathematicians and the set of people with Real Jobs, but let's not dwell on that.) I finally did read it, though.

It was a fun read. I guess I already learned a fair amount about crackpots back when I lurked on Usenet, back when people used to talk on Usenet. (Usenet used to be more about discussion than about warez. I think. At least the groups I hung out on were full of discussion.) So I knew the general advice:

- When a crank tells you his wrong theory, you might tell him he's wrong; you might keep quiet.
- When you point out a flaw in the crank's argument, don't be surprised if they "disprove" your statement with an argument along the lines of "layler layler layler I'm not listening!"
- Don't sic the crank on someone else; that's mean.

This book has more. It has anecdotes. It has correspondence between cranks and mathematicians who have received crankmail. It follows the development of some cranks over the years. It has stories. It has more trends to watch out for.

- If you point out the first problem in a many-problemed "proof", the crank will figure out a way to replace that first problem with a new problem--and then claim you agree with them.
- If you say "This 'proof' just doesn't hold together," the crank will say, "No-one can point out a specific problem with my proof."

I didn't follow all of this book. Some of the math was over my head. But most of it was pretty accessible. And you don't need to know math for the most part: my crank was pretty typical: "prove" something by declaring it true and waving your hands.

Reading through this book, I think I got away easy. I've received mail from one mathematical crank. If I worked at a university math department, more cranks would target me. Maybe that was this book's most encouraging message: it could have been worse. I could have received mail from someone who was enraged at the very notion of... of... of a Menger sponge. Or they could offer a "proof" of something in number theory. I never know how to disprove anything in number theory.

Every university should have a copy of this book in their library, for the sake of whatever junior professor gets the task of responding to crank mail and needs to look up that number of the form 6p+43 which is not a square number, this disproving some common crank theory. (I just made that up, but you get the idea.) And that library should be open on weekends. Please?