## sauna@home

Was in a sauna with my father today when the talk turned to the sauna itself.

Namely, “wouldn’t it be nice to have a function to describe the time one could bathe in a sauna before it got too cold, given certain inputs about the warming and the construction of the sauna?”

The inputs we deemed necessary were things like the “natural” temperature (before the sauna is warmed any), the amount and quality of wood used, the interior dimensions of the sauna room and the amount of ventilation, the heat retentivity of the stove itself and of the walls, the number of people bathing, the type and amount of water-flinging being done, and the like.

This then turned to a talk about how to best get empirical results about the effects of each of these variables, and the kind of mathematical (or computorial) trickery necessary to get a huge weird-ass polynomial approximation (probably funky towards the edges) out of the snarl of data points.

And whether it would be a reasonable M. Sc. (or the engineering equivalent) project to get a student in some school with a sauna on the premises to make educated guesses about the relationships of some key variables, and then determine the constants in those relationships with a bit of experimentation. Say, “the mean bath time B is related to the amount of wood w, the bather number b, and the number of stones on the sauna stove s by a relation like B = Lw exp(Ks)/b, where K and L are constants to be determined”. (This is probably a silly guess; but then I am not a physics kind of a guy. I do mathematics, and what I want, I define to be so. Reality is overrated.)

Giving this kind of a project to some poor student would then lead to a conversation like this:

“Hey! What’re you doing today after school? ‘School’ heh heh, university’s not a school. Snigger snigger.”

“Er, I’m all tied up with this M.Sc. project of mine. I was wondering, could you stay and help me a bit. I need one more warm body to get a data point I’m curious about. You’re round 200 lbs, aren’t you?”

“Eh, what?”

Also, the huge number of data necessary to make reasonably educated guesses was noted. If you bathe once a day, you still won’t get more than round 350 data points a year, and that’s not much if you have a dozen variables! Besides, to determine “how long you can bathe” means bathing until the sauna’s cold, and that takes longer than most normal sauna sessions last. (A good sauna can bathe three disjoint sets of people, though the last ones will be sucking out the last hisses and steam. An individual bathing is anything from half an hour to two or three or more.) To help this, something immediately dubbed “sauna@home” was proposed, though it seemed necessary to give each participant first a big pile of blueprints to get the same kind of a sauna for each; otherwise too much data. (And one more variable: air pressure! Suppose one subscriber is at the top of Mt. Halti or something.)

So if you have occasion to wonder how I came to be the way I am, why yes, it is hereditary.

(And this is all about saunas warmed with burning wood, because the electrically warmed ones… well, the difference’s like the one between kissing a girl and kissing a she-bear. Both can do for a while, but only the first is something you might want to go on doing forever.)