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The Straight Dope 

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I have an old apartment complete with old pipes and I've noticed an annoying phenomenon when I turn on the hot water. At first it comes blasting out, but within a short time it slows to a trickle, as though a poltergeist were under the floor squeezing the pipe. What gives? The pipe stays the same and I assume the water pressure does too. Is there some law of fluid dynamics that causes this? It doesn't seem to happen to cold-water pipes. --Mike Persons, Dallas, Texas

Cecil would love to tell you there's some mind-boggling phenomenon at work here involving gravitons and the strong nuclear force, Mike, but, unfortunately, no can do. According to my Plumbing Repairs Made Easy--I love books with titles like this--the hot water slows to a trickle because the washer in the faucet expands when it gets hot. Solution? "Replace with a proper, nonexpanding washer." Short, simple, and unlikely to inspire much back talk from the troops. Sometimes I think I went into the wrong line of work.

It's 2:30 AM. It's Friday morning. There's a bluesy tune on KNON. And I'm finally making the big move. Why does my reflection turn upside down in my entire stock of spoons? I have a feeling you're the man with the straight dope. --Monica, Dallas

PS: Enclosed is exhibit A.

Now wait a second, Monica. We have a bad segue here. We've got this late-night scene, you're building the mood, then all of a sudden we slam into this business about the spoons. Very disorienting. Try to work on this.

Now to business. Touched though I am by the thought, it wasn't necessary for you to enclose the spoon. They all work the same way--the bowl acts as a "parabolic reflector." (It's not a perfect parabola, and it's not a perfect reflection, either.) Light coming from above is reflected down, light coming from below is reflected up, and the result is an inverted image. We thus have a remarkable thing: a mirror that reverses up and down but not left and right. Certainly a pleasant change from the usual humdrum routine.

The whole business of curved reflecting surfaces is pretty interesting, and not just to people in the fun-house mirror business. I'm told that somebody has designed a mirror that uses a complex combination of concave and convex surfaces to produce a "right-reading" image--a mirror, in other words, that allows us to see ourselves as others see us. Robert Burns would have been proud.

I'm sure you've seen those clear plastic glass containers filled with a liquid and tiny flakes of "snow" or some other material. When you turn or shake them, you create a "snowstorm" inside. My question is, what do you call these things? I feel so inadequate when I'm trying to describe that scene in Citizen Kane. --Larry Raymond, Richardson, Texas

Get ready for this, Lar. You call them "shake-'em-ups." You were expecting maybe gynotikolobomassophile?

FROM THE TEEMING MILLIONS

I am writing to point out a medical error in your column of November 27. You are incorrect in stating that "X rays were once used to treat benign enlargements of the thyroid, for instance, triggering many cases of thyroid cancer." The X ray treatments you are referring to that have been linked to thyroid tumors were used to treat enlargements of the thymus gland, enlarged tonsils and adenoids, enlarged lymph nodes in the neck, birthmarks, acne, and other conditions. In contrast, radioactive iodine has been and continues to be used widely and successfully to treat overactivity of the thyroid gland (hyperthyroidism). Very large and careful studies have demonstrated its usefulness and safety. I hope the error in your column will not dissuade people from receiving one of the appropriate treatments for hyperthyroidism. --Arthur Schneider, MD, PhD, director, endocrinology and metabolism division, department of medicine, Michael Reese Hospital and Medical Center, Chicago

When you're taking notes, doc, never abbreviate "thymus" and "thyroid." My apologies.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.

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