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Spiller Alert: This post may contain TMI about Miracle Workers and Bodily Fluids. You can stop now.

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“It wasn’t there in 2009, so that’s a bit suspicious,” I heard the CAT-scan doctor say. He wasn’t talking to me, thank God, because I hadn’t had my CAT scan yet, but it gave me pause for thought and gratitude.

The other day while teaching I suddenly briefly felt really ill with a pain in my lower back and then broke out in a copious cold sweat over every part of me; even the hair on my head was as wet as though I’d had a five mile run. I thought it was a muscle or bone pain from running that had gotten exacerbated, but, after thinking a while and really not feeling too good, I wondered if it mightn’t be a recurrence of a kidney stone I once had, which hadn’t been too bad at all.? Because I was supposed to go on a long airplane trip the following day, I went to the kidney stone doctor, a very nice man who saw me on short notice at 5 in the afternoon.

He poked and ultrasounded and saw nothing. If you have a kidney stone that’s blocking things on its way out, he explained, it causes fluid to back up into the appropriate kidney, and that fluid shows up as dark stuff on the ultrasound. There wasn’t any. The only way that wouldn’t be the case, he told me, was if the blockage had just happened and there hadn’t been time for backing up.

As a precaution he decided to look at the appropriate fluid and dipped a stick into a cup of it, which turned green, indicating a scratch somewhere upriver. What I’d had when I’d been in pain and sweating was renal colic, he told me, and my sweating had something to do with a vagus nerve. Then, bragging about how easily available top-notch medical care was in New York City, he sent me for a CAT scan right around the corner at 6 pm in the evening, in an Imaging Center where they were still busily working away. (They’re open on Saturdays too.) He also told me parenthetically that one day, when socialized medicine had overwhelmed him, too, he wouldn’t be able to respond with a CAT scan, but would have to follow some bureaucratic procedure that indicated what he was allowed to do given my symptoms. Who was I to argue?

No more than twenty minutes later they had (i) run me through the machine, (ii) seen a stone trying to make its way out, (iii) called my doctor, (iv) put him on the phone to me. All of them told me a long flight wasn’t the right place to be when the stone tried to escape again.

I chatted for a while to the CAT-scan doctor, who showed me my pictures and gave them to my on a CD.

“Fantastic how you can do this,” I said with admiration at the fact that they were actually doing somebody some good with all their mathematics that lies behind cat scanning, something I know a small amount about.

“It’s the machines we have,” he replied.

The mathematics of computerized tomography led to a Nobel prize for Alan Cormack, a University of Cape Town (ahem) physicist at the time of his publications on the subject in 1963/4, in a physics department that had had a long history of X-ray diffraction work. Behind my scan was some fundamental physics? and mathematics and then some really effective engineering, and I’m grateful for it. I just printed off his Nobel acceptance speech and I’m intending to read it.

(For those of you in finance, computerized tomography is a kind of calibration, like trying to figure out forward rates from bond yields or local volatilities from implied volatilities. Physicists call it inverse scattering — given the scatter, try to figure out the nature of what caused it. The difference is that it really works in medicine because it’s talking about something real you can do something about.)

Years ago, a good diagnostician would merely have stuck fingers into me and tried to figure out what was happening. Now, though my doctor did that too, he could get really detailed confirmation about location and size.

What fundamental theory and real engineering can do is amazing and accurate. Economists occasionally suggest that we have a similar investigative approach to economic diagnosis, but of course it isn’t possible. There are too many contributing causes to a human accident. A physical malfunction is often (not always) much clearer. Trying to understand what causes economic catastrophes is more like trying to understand what causes some mental illnesses — a host of things, perhaps.

So here I am, having been through Genesis and Numbers, and now waiting for Exodus and the crossing of the Red Sea. Meanwhile I’m feeling pretty OK, and went for a run in the park for the first time in a while and worked up a genuine non-vagus sweat.