Q. Traveling in the western United States, I couldn't fail to notice that radio and television stations there start with a "K" (as in KTLA), while in the East they start with a "W" (as in WETA). Why? What is the meaning (if any) of the "K", the "W" and the rest of the letters? And why are there always four letters?

Edward Peet

District

A. We'd love to reveal a cryptic meaning to the "K" and "W" in broadcast call letters -- maybe something as mysterious as that creepy eyeball-in-the-pyramid thing on the $1 bill.

Unfortunately, the official Federal Communications Commission (FCC) explanation is distressingly prosaic. In 1927, when wireless communications were getting to be a pretty big deal, folks started to need distinctive ways to identify radio broadcasts from different countries and to specify sources within a single country.

So an international group convened and parceled out letters for each country to use. The United States ended up with "K" and the phonetically cumbersome "W". We also were assigned "N" for Navy and Coast Guard radio, and we share "A" for certain Army and Air Force broadcasts.

The original idea was that U.S. stations in the West would use the "K" prefix, whereas eastern broadcasters were stuck with the dreaded "W". There are exceptions -- a "K" in Pittsburgh, for example -- but for the most part, "K" is west of the Mississippi River and "W" east.

Three letters were sufficient in the early days, and there are still many triliterate stations, including WOL and WRC right here in the greater metropolitan area. But most have four.

In 1941, when television and FM radio started hitting the airwaves in earnest, stations weren't required to obtain new call letters if they were operated by the same outfit that already had an AM license. Many outlets just added an "-FM" or "-TV" to their existing call sign.

Today, there are about 13,000 radio stations in the United States, and new ones must apply to the FCC for desired letter combinations on a first-come, first-served basis. Applications can now be made on-line.

Your choice may already be taken by some of the thousands of previous requests, including WGN ("World's Greatest Newspaper") in Chicago; WIOD ("Wonderful Isle of Dreams") in Miami; WMTC ("Win Men to Christ") in Vancleve, Ky.; and our particular favorite, WGCD in Chester, S.C. That's "Wonderful Guernsey Center of Dixie." Moo.

What is the incidence of left-handedness in the general population? What famous people throughout history have been left-handed? Does this condition have severe positive or negative social effects other than mere inconvenience?

E. Taylor

Upper Marlboro

That's a sinister question, to use the Latin word for "left side." Dexter, by the way, is Latin for "right side" and also meant dexterous, propitious or favorable. Sound a little unfair? Our word gauche, meaning dorky or awkward, comes from the French for "left." In many Muslim cultures, the left hand is regarded as "unclean"; folks eat only with the right. Tonier eateries still serve from the left and take from the right.

But we digress.

Nobody knows the exact incidence of left-handedness. Best estimates are about 8 to 10 percent. Genes may play a role; learning and environment certainly do.

Whatever, development of a dominant hand happens fairly late in childhood, rarely emerging before age 2 and often not until 6. Your dominant foot and/or eye, however, may be on the other side of your body. Go figure.

The way you end up may have something to do with which side of the brain happens to dominate when it's time to choose sides. Changing your "laterality" later may cause problems, such as stammering.

There have been so many famous left-handers -- from Leonardo da Vinci to Babe Ruth, Ben Franklin, Judy Garland and (maybe) Albert Einstein -- that southpaws might seem to suffer few, if any, adverse effects from a world listing to starboard.

Some studies have suggested that lefties may die sooner than righties on average, but this has never been proven. Moreover, owing to the fabled social concern of modern industry, more and more products such as scissors and power tools are being designed for sinistral folks. If you've just got to shift gears on the left, though, move to Britain.

There is no doubt, however, that much of the modern world seems built exclusively for northpaws. Try putting your Metro ticket into the turnstile with your left hand some time. For an overview of these and other lefty issues, we recommend looking at http:// duke.usask.ca/~elias/left/.

Do sounds travel farther and stronger on humid days? It seems that I can hear more noises from cars, etc., on foggy days that on clear ones. What is going on here?

Len Taylor

Gaithersburg

We were set to toss this question into our special file labeled "Well-Meaning But Demented." After all, the whole idea seems ridiculous: If you've got a bunch of relatively heavy water molecules just hanging around in the air, how could they possibly do anything but muffle sound like a sort of vaporous curtain? Case closed.

Then, in an unaccustomed fit of good sense, we called a couple of experts and found out that the questioner is completely correct.

In fact, there are at least three excellent reasons why you can hear many sounds better on a foggy day.

One, explains Henry Bass, director of the National Center for Physical Acoustics at the University of Mississippi, is a simple matter of refraction. Sound is a wave, and waves change direction when they pass from a medium of one density into another.

Recall how light is bent by a prism or lens. That's what happens when a wave passes from a less dense medium -- air -- into the more dense medium of the lens glass.

On a "typical clear day," Bass says, "when you have heating of the ground by the sun, it forms a temperature gradient between the surface, which is hot, and the upper layers which are cooler [and thus more dense]. That in turn causes sound generated near the surface to bend upward," away from your ear.

But on a classic foggy day, less sunlight reaches the surface, and those pesky temperature/density differences are minimized. Result: Sounds from ground-level sources proceed more directly toward your ear.

Moreover, Bass says, "fogs almost always occur in the absence of wind." And wind, as you know if you've tried yelling into a gust coming toward you, restricts propagation of sound in the direction from which the wind is blowing. On a calm day, though, sound reaches you just as easily from all directions.

Wait, there's more! It turns out that much of the energy in sound waves traveling through dry air is absorbed as nitrogen, oxygen and carbon dioxide molecules bang into one another at their characteristic vibration frequencies.

But the presence of high relative humidity reduces that effect. Above 40 percent humidity or so, frequencies in the prime audible range of 1,000 to 10,000 cycles per second are transmitted much more easily.

So just about the time you're thoroughly miserable in the grip of Washington's steamy summers, everybody's air conditioners suddenly become easier to hear. Swell.

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