*over 40*-- showed up in an algorithms class. This was firmly an undergrad class, so he couldn't just be a conspicuously creaky grad student. There must have been some oddball situation to explain his presence.

He was annoying. He asked questions all the time, usually about things no one cared about. You might think the professor would be annoyed, too, but he seemed to know this guy in some way. They'd go on and on about some esoteric bit of junk that certainly wasn't going to help me do the homework.

His favorite question was "what about the empty set?" That needs explaining, but it's simple: in set theory, you can have sets of things (set theory is the

*best-named theory*). If there's nothing in a set, it's called the empty set (see? those folks can

*name!*) and abbreviated ∅. A lot of algorithms have to handle the empty set in a special way.

So what this winner was asking, over and over, was essentially "how does this particular algorithm handle this thing that all algorithms need to deal with?" It's the sort of question that lets you seem smart without knowing much. We dubbed this guy the Keeper ∅f The Empty Set, or K∅TES. It was catchy -- we had t-shirts printed; we wrote a theme song. OK, not really, but we did roll our eyes whenever he opened his mouth. I mean, why did this guy need to be the center of attention?

...

This Tuesday, 15 years later, I was a creaky 35-year-old sitting in a classroom surrounded by 20-somethings. This was kind of an oddball situation: I'm taking this class because I need to get accepted into a PhD program that I don't really have the background for. It's a small program, the kind where everybody pretty much knows each other.

I need to prove to the department that I can do the classwork. Here's what I worked out: the professor will write a "recommendation" letter to the department describing my performance in class,

*however I do*. If I do badly, the letter will say "send this dork the thin envelope" and I'll be throwing away the $85 application fee and a whole lot of time. I have one goal, here: impress the professor.

I talked to the prof ahead of time, so he kind of knows me. I don't have all the background that the kids actually taking the class for credit do, but I have other areas of expertise. So I ask questions that are a little off the topic of the lecture, about related esoteric junk that the prof might be interested in but that won't help anybody do the homework.

And getting a chance to ask questions is no problem. Turns out -- and, man, I wish I'd realized this a decade or so earlier -- 20-somethings have pretty much zero self-confidence in class! So the prof will ask a question, and there will be silence, and then crickets, and the crickets will complete the entire first movement of Cricket Symphony #3, and then I'll pipe up and try to score some points.

I'm sure that gets pretty old for the other students. What I'm really curious about is the nickname they've chosen for me. I hope it's catchy.