Do Penguins Have Knees?

by David Feldman

  Most mosquitoes concentrate all of their activities into a short period of the day or evening, usually in one to two hours. If they bite at night, mosquitoes will usually eat, mate, and lay eggs then, too. Usually, nocturnal and crepuscular female mosquitoes are sedentary, whether they are converting the lipids of blood into eggs or merely waiting to go on a nectar-seeking expedition to provide energy. Although they may take off once or twice a day to find some nectar, a week or more may pass between blood meals.

  If the climatic conditions stay constant, mosquitoes tend to stick to the same resting patterns every day. But according to Charles Schaefer, director of the Mosquito Control Research Laboratory at the University of California at Berkeley, the activity pattern of mosquitoes can be radically changed by many factors:

  1. Light (Most nocturnal and crepuscular mosquitoes do not like to take flight if they have to confront direct sunlight. Conversely, in homes, some otherwise nocturnal mosquitoes will be active during daylight hours if the house is dark.)

  2. Humidity (Most will be relatively inactive when the humidity is low.)

  3. Temperature (They don’t like to fly in hot weather.)

  4. Wind (Mosquitoes are sensitive to wind, and will usually not take flight if the wind is more than 10 mph.)

  Where are nocturnal mosquitoes hiding during the day? Most never fly far from their breeding grounds. Most settle into vegetation. Grass is a particular favorite. But others rest on trees; their coloring provides excellent camouflage to protect them against predators.

  A common variety of mosquito in North America, the anopheles, often seeks shelter. Homes and barns are favourite targets, but a bridge or tunnel will do in a pinch. Nocturnal or crepuscular mosquitoes are quite content to rest on a wall in a house, until there is too much light in the room. In the wild, shelter-seeking mosquitoes will reside in caves or trees.

  We asked Dr. Schaefer, who supplied us with much of the background information for this Imponderable, whether mosquitoes were resting or sleeping during their twenty-two hours or so of inactivity. He replied that no one really knows for sure. We’re reserving When Do Mosquitoes Sleep? as a possible title for a future volume of Imponderables.

  Submitted by Jennifer Martz of Perkiomenville, Pennsylvania. Thanks also to Ronald C. Semone of Washington, D.C.

  What Does the “CAR-RT SORT” Printed Next to the Address on Envelopes Mean?

  Reader Jeff Bennett writes: “CAR-RT SORT is printed on a lot of the letters I receive. Obviously it’s got something to do with mail sorting, but what does it stand for?”

  Not unlike us, Jeff, it sounds like you’ve been receiving more than your share of junk mail lately. CAR-RT SORT is short for Carrier Route Presort and is a special class of mail. As the name implies, to qualify for the Carrier Route First-Class Mail rate, mailers must arrange all letters so that they can be given to the appropriate mail carrier without any sorting by the postal system. Each piece must be part of a minimum of ten pieces for that carrier; if there are not ten pieces for a particular carrier route, the mailer must pay the rate for Presorted First-Class Mail. (Presorted First-Class Mail costs more than Carrier Route because it requires only that the mail be arranged in ascending order of ZIP code.)

  Don’t expect to see CAR-RT SORT on the envelopes of your friends’ Christmas cards. Carrier Route Mail must be sent in a single mailing of not less than 500 pieces. And if they really have ten friends serviced by one postal carrier, it would be cheaper for them to hand-deliver the cards.

  Submitted by Jeff Bennett of Poland, New York. Thanks also to Matt Menentowski of Spring, Texas.

  Why Was “pi” Chosen as the Greek Letter to Signify the Ratio of a Circle’s Circumference to Its Diameter?

  The history of “pi” is so complex and fascinating that whole books have been written about the subject. Still, if you want to make a long story short, it can be boiled down to the explanation provided by Roger Pinkham, a mathematician at the Stevens Institute of Technology in Hoboken, New Jersey:

  There are two Greek words for perimeter, perimetros and periphireia. The circumference of a circle is its perimeter, and the first letter of the Greek prefix peri (meaning “round”) used in those two words was chosen.

  Mathematicians attempted to calculate the pi ratio before the birth of Christ. But it wasn’t the ancient Egyptians or Greek mathematicians who first coined the term. San Antonio math teacher John Veltman sent us documentation indicating that although pi was earlier applied as an abbreviation of “periphery,” the first time it was found in print to express the circle ratio was in 1706, when an English writer named William Jones, best known as a translator of Isaac Newton, published A New Introduction to Mathematics. “Pi” did not enjoy widespread acceptance until 1737, when Jones’s term was popularized by the great Swiss mathematician Leonhard Euler.

  So what did the ancient Greeks call the ratio? They probably did not have a handy abbreviation. Veltman explains:

  It appears that even the Greek mathematicians themselves did not use their letter pi to represent the circle ratio. Several ancient cultures did their math in sentence form with little or no abbreviation or symbolism. It is amazing how much they achieved without such an aid. Archimedes, born about 287 B.C., is said to have determined that the value of pi was between 3 10/71 and 3 1/7 (or in our decimal notation, between 3.14084 and 3.142858).

  In the centuries that followed, mathematicians in other countries produced even more precise calculations: Around A.D. 150, Ptolemy of Alexandria weighed in with his value of 3.1416. Around A.D. 480, a Chinese man, Tsu Ch’ung-chih, improved the figure to 3.1415929, correct to the first six numbers after the decimal point.

  Why is our mathematical vocabulary a seemingly random hodgepodge of Greek and Latin terminology? Why do we say the Latin-derived “circumference” (originally meaning “to run or move around”) rather than the Greek “periphery”? Diane McCulloch, a mathematician at the Mount de Chantal Academy in Wheeling, West Virginia, explains:

  The Greeks were more avid mathematicians than the Romans, who preferred the practical uses and didn’t have much time for the analytical aspect of mathematics. Thank goodness the writings of the Greeks were preserved by the Islamic scholars. We have access to the ancient Greek mathematical work because these Islamic scholars established libraries in Spain; when they were eventually driven out of Spain, their books were translated into Latin and then into other European languages, which themselves tended to be derived from Latin.

  Therefore, we use the word “triangle” when the Greeks would probably have used the word “trigon,” as in “polygon,” “octagon,” etc.

  Submitted by Dennis Kingsley of Goodrich, Michigan.

  Why Can’t You Buy Macadamia Nuts in Their Shells?

  Macadamia nuts do have shells. But selling them in their shells would present a serious marketing problem. Only Superman could eat them. According to the Mauna Loa Macadamia Nut Corporation, the largest producer of macadamias in the world, “It takes 300-pounds-per-square-inch of pressure to break the shell.”

  After macadamias are harvested, the husks are removed, and then the nuts are dried and cured to reduce their moisture. The drying process helps separate the kernel from the shell; without this separation, it would be impossible to apply the pressure necessary to shatter the shell without pulverizing the contents. The nuts then pass through counter-rotating steel rollers spaced to break the shell without shattering the nutmeat.

  Of course, one question remains. Why did Mother Nature bother creating macadamias when humans and animals (even raging rhinos) can’t break open the shells to eat them without the aid of heavy machinery?

  Submitted by Herbert Kraut of Forest Hills, New York.

  If Heat Rises, Why Does Ice Form on the Top of Water in Lakes and Ponds?

  Anyone who has ever filled an ice-cube tray with water knows that room temperature water decreases in density when it freezes. We also know that heat rises. And that the sun would hit the top of the water
more directly than water at the bottom. All three scientific verities would seem to indicate that ice would form at the bottom, rather than the top, of lakes and ponds. “What gives?” demand Imponderables readers.

  You may not know, however, what Neal P. Rowell, retired professor of physics at the University of South Alabama, told us: Water is most dense at 4 degrees Centigrade (or 39.2 degrees Fahrenheit). This turns out to be the key to the mystery of the rising ice. One of our favorite scientific researchers, Harold Blake, wrote a fine summary of what turns out to be a highly technical answer:

  As water cools, it gets more dense. It shrinks. It sinks to the bottom of the pond, lake, rain barrel, wheelbarrow, or dog’s water dish. But at 4 degrees Centigrade, a few degrees above freezing, the water has reached its maximum density. It now starts to expand as it gets cooler. The water that is between 4 degrees Centigrade and zero Centigrade (the freezing point of water) now starts to rise to the surface. It is lighter, less dense.

  Now, more heat has to be lost from the water at freezing to form ice at freezing. This is called the “heat of fusion.” During the freezing process, ice crystals form and expand to a larger volume, fusing together as they expand, and using more freezing water to “cement” themselves together. The ice crystals are very much lighter and remain on the surface.

  Once the surface is frozen over, heat dissipates from the edges and freezing is progressive from the edges. When the unfrozen core finally freezes, there is tremendous pressure exerted from the expansion, and the ice surface or container sides yield, a common annoyance with water pipes.

  Once the top layer of the lake or pond freezes, the water below will rarely reach 0 degrees Centigrade; the ice acts effectively as insulation. By keeping the temperature of the water below the ice between 0 and 4 degrees Centigrade, the ice helps some aquatic life survive in the winter when a lake is frozen over.

  The strangest element of this ice Imponderable is that since water at 4 degrees Centigrade is at its maximum density, it always expands when it changes temperature, whether it gets hotter or cooler.

  Submitted by Richard T. Mitch of Dunlap, California. Thanks also to Kenneth D. MacDonald of Melrose, Massachusetts; R. Prickett of Stockton, California; Brian Steiner of Charlotte, North Carolina; and John Weisling of Grafton, Wisconsin.

  What Happens to the 1,000 or More Prints After Films Have Finished Their Theatrical Runs?

  Distribution strategies for films vary dramatically. A “critics’ darling,” especially a foreign film or a movie without big stars, might be given a few exclusive runs in media centers like New York City and Los Angeles. The film’s distributor prays that word-of-mouth and good reviews will build business so that it can expand to more theaters in those cities and later be distributed throughout the country.

  “High-concept” films, particularly comedies and action films whose plot lines can be easily communicated in short television commercials, and films starring “bankable” actors are likely to be given broad releases. By opening the film simultaneously across the country at 1,000 to 2,000 or more theaters, the film studios can amortize the horrendous cost of national advertising. But the cost of duplicating 2,000 prints, while dwarfed by marketing costs, is nevertheless a major expense.

  A run-of-the-mill horror film from a major studio, for example, might open in 1,500 theaters simultaneously. The usual pattern for these films is to gross a considerable amount of money the first week and then fall off sharply. A horror film without good word-of-mouth might be gone from most theaters within four weeks. Of course, studios will release the film on videotape within a year, but what will they do with those 1,500 prints?

  The first priority is to ship the prints overseas. Most American films are released overseas after the American theatrical run is over. Eventually, those American prints are returned to the United States.

  And then they are destroyed and the silver is extracted from the film and sold to precious metals dealers. The studios have little use for 1,500 scratchy prints.

  Mark Gill, vice-president of publicity at Columbia Pictures, told Imponderables that his company keeps twenty to thirty prints of all its current releases indefinitely. The film studios are aware of all of the movies from the early twentieth century that have been lost due to negligence—some have deteriorated in quality but others are missing simply because nobody bothered keeping a print. With all of the ancillary markets available, including videotape, laser disc, repertory theaters, cable television, and syndicated television, today’s movies are unlikely to disappear altogether (though we can think of more than a few that we would like to disappear). But the problem of print deterioration continues.

  Submitted by Ken Shafer of Traverse City, Michigan. Thanks also to John DuVall of Fort Pierce, Florida.

  Why Is Balsa Wood Classified as a Hardwood When It Is Soft? What Is the Difference Between a Softwood and a Hardwood?

  Call us naive. But we thought that maybe there was a slight chance that the main distinction between a softwood and a hardwood was that hardwood was harder than softwood. What fools we are.

  Haven’t you gotten the lesson yet? LIFE IS NOT FAIR. Our language makes no sense. The center will not hold. Burma Shave.

  Anyway, it turns out that the distinction between the two lies in how their seeds are formed on the tree. Softwoods, such as pines, spruce, and fir, are examples of gymnosperms, plants that produce seeds without a covering. John A. Pitcher, director of the Hardwood Research Council, told Imponderables that if you pull one of the center scales back away from the stem of a fresh pine cone, you’ll see a pair of seeds lying side by side. “They have no covering except the wooden cone.”

  Hardwoods are a type of angiosperm, a true flowering plant that bears seeds enclosed in capsules, fruits, or husks (e.g., olives, lilies, walnuts). Hardwoods also tend to lose their leaves in temperate climates, whereas softwoods are evergreens; but in tropical climates, many hardwoods retain their leaves.

  While it is true that there is a tendency for softwoods to be softer in consistency (and easier to cut for commercial purposes), and for hardwoods to be more compact, and thus tougher and denser in texture, these rules of thumb are not reliable. Pitcher enclosed a booklet listing the specific gravities of the important commercial woods in the U.S. He indicates the irony:

  At 0.16 specific gravity, balsa is the lightest wood listed. At a specific gravity of 1.05, lignumvitae is the heaviest wood known. Both are hardwoods.

  Do Earlobes Serve Any Particular or Discernible Function?

  Our authorities answered as one: Yes, earlobes do serve a particular function. They are an ideal place to hang earrings.

  Oh sure, there are theories. Ear, nose, and throat specialist Dr. Ben Jenkins of Kingsland, Georgia, remembers reading about a speculation that when our predecessors walked on four feet, our earlobes were larger “and that they fell in [ward] to protect the ear canal.” Biologist John F. Hertner recounts another anthropological theory: that earlobes served as “an ornament of interest in sexual selection.”

  Doctors and biologists we confront with questions like these about seemingly unimportant anatomical features are quick to shrug their shoulders. They are quite comfortable with the notion that not every organ in our body is essential to our well-being and not every obsolete feature of our anatomy is eliminated as soon as it becomes unnecessary.

  Actually, the opposite is closer to the truth. Anatomical features of earlier humankind tend to stick around unless they are an obvious detriment. As Professor Hertner puts it,

  Nature tends to conserve genetic information unless there is selection pressure against a particular feature. Our bodies serve in some respect as museums of our evolutionary heritage.

  Submitted by Dianne Love of Seaside Park, New Jersey.

  Why Does Butter Get Darker and Harder in the Refrigerator After It Is Opened?

  Butter discolors for the same reason that apples or bananas turn dark—oxidation. And although butter doesn’t have a peel to protect i
t from the ravages of air, it does have a snug wrapper surrounding it until it is first used by the consumer. Only after the wrapper is eliminated or loosened does the butter darken.

  Why does it get harder? The cold temperature in the refrigerator causes the moisture in the butter to evaporate. Many other foods, such as peanut butter and onion dip, become less plastic when refrigerated because of evaporation of liquid.

  Submitted by Mitchell Hofing of New York, New York.

  Why Are Dance Studios Usually Located on the Second Floor of Buildings?

  Truth be told, the quality of Imponderables we receive on call-in talk shows is usually distinctly inferior to the stuff in our mailbag. But Los Angeles talk-show host Carol Hemingway has an imaginative gang of listeners, and this question was posed to us on her gabfest.

  We loved it. This was an Imponderable deeply embedded in our subconscious. We have traveled through small towns with only one two-story commercial building in them. If there was a dance studio in town, it was located in that building. On the second floor.

  We recently saw film critic Roger Ebert wax nostalgic about his first date. He asked his friend to a dance at Thelma Lee Ritter’s studio in Urbana, Illinois. Unfortunately, the dance was canceled. But not all was lost—Ms. Ritter’s second-floor studio was located above the Princess Theater. So Roger and his date went to the movies.