When Do Fish Sleep?

by David Feldman

  Those spaces that threaten the well-being of your mother’s back are a form of “tooled joints,” strategically positioned cracks. These joints are placed in all types of concrete slabs. Gerald Voigt elaborates:

  The concrete is sawed or tooled to approximately one-quarter of the thickness of the slab, which creates a “weakened plane.” The concrete will crack through the “weakened plane” joint, because that joint is not as strong. As you can see on almost any sidewalk, tooled joints are placed about every four to eight feet. These joints are placed to control where cracks develop and avoid random cracking which is usually considered unattractive…. Typically sidewalks are four inches thick; joint depth must be at least one-quarter of the sidewalk thickness.

  Perhaps the most surprising element in the story of concrete cracks is that although so much effort is put into preventing them, cracks are not particularly troublesome. The National Ready-Mixed Concrete Association says that cracks rarely affect the structural integrity of concrete. Even when the cracks are wide enough to allow water to seep in, “they do not lead to progressive deterioration. They are simply unsightly.”

  Incidentally, our correspondent asked how the superstition “Step on a crack, break your mother’s back” originated. We’ve never found a convincing answer to this Imponderable, but Gerald Voigt offered a fascinating theory:

  Since a concrete sidewalk consists of many short segments (slabs) of white concrete, it can be imagined that it is like a human spine. The spine also consists of many short segments (vertebrae) of white bones. The weak links in each system are the joints. Stepping on a sidewalk crack, or joint, is analogous to stepping on the weakest area of the spine. I imagine if I were walking down a spine, I would avoid stepping on a vertebrae link, wouldn’t you?

  Submitted by Mrs. Harold Feinstein of Skokie, Illinois. Thanks also to Henry J. Stark of Montgomery, New York.

  Why Do We Have to Shake Deodorant and Other Aerosol Cans Before Using?

  If you could see inside a can of deodorant, you would see that the ingredients are not arranged uniformly in the can. The propellant is not soluble and so won’t mix with the active ingredients in the deodorant.

  In many cases, you would see three or four levels of ingredients in a can. The top layer would contain the hydrocarbon gas used as a propellant. Other active ingredients, such as aluminum salt, emollient, and fragrance, also might seek their own level. By shaking up the can, you would guarantee spraying the proper proportion of ingredients.

  Any effort expended in shaking the can is well worth the appreciation from friends and loved ones. But a stiff spray of hydrocarbon gas simply isn’t sufficient to take care of a nasty body odor problem.

  Submitted by Mark Fusco of Northford, Connecticut.

  Why Do Airlines Use Red Carbons on Their Tickets?

  The dominant manufacturer of airline tickets is Rand McNally, the same company that makes maps and atlases. We spoke to Chris George, of Rand McNally’s Ticket Division, who told us that there are two explanations for the tradition of red carbons.

  In the early years of commercial aviation, black carbons were used. This we know for a fact. But Mr. George says the problem with black carbons was that in high humidity specks of black would fall off the ticket. Women, in particular, were upset that their hands or gloves were befouled with black crud. So the airlines did market research that revealed women did not object as much to traces of red on their hands because they were used to rouge and lipstick stains. This, Mr. George adds wryly, is the romantic explanation.

  The unromantic explanation (a.k.a. the truth) is as follows: Once your ticket form is torn by the ticket agent, it is sent to the accounting department of the airline. The major carriers have long used optical scanners to read the serial numbers found on each ticket. An OCR (Optical Character Recognition) scanner can’t read the ticket when black flecks of carbon land on the serial number because it can only register information printed in black ink. Much as a photocopier will not read blue ink, an OCR scanner won’t read red ink. Who would have thought that accountants would be responsible for the daring flash of red on airline tickets?

  In a time of high-tech stationery, why don’t the airlines use carbonless paper? Part of the answer again relates to the OCR equipment. Carbonless paper contains blue specks that OCRs won’t read. Furthermore, with chemically sensitized noncarbon paper, legibility is good for only about five copies. Old-fashioned carbon paper can render nine legible copies, sometimes necessary for the daunting itineraries of business travelers.

  Now that most airlines are issuing automated ticket boarding passes—the ones that look like computer cards—the decline of the carbonized form is inevitable. Because not all ticket counters possess the equipment to issue these boarding passes, Mr. George predicts that the beloved red carbonized forms will continue to play a part in aviation for the foreseeable future.

  Submitted by Niel Lynch of Escondido, California.

  I Have a Dollar Bill with an Asterisk After the Serial Number: Is It Counterfeit?

  The Imponderables staff will gladly accept your dollar bill if you don’t want it. No, it’s not counterfeit. You are holding a “star note,” a replacement for a defective bill that has been destroyed.

  In 1910, the Bureau of Engraving and Printing started printing B and later D as prefixes before the serial numbers of replacement notes. No star notes were issued for national bank notes, which were replaced by new notes that matched the missing serial numbers.

  Now that notes are issued in series of one hundred million at a time, it is obvious why the Bureau would rather not have to renumber replacement notes, especially since, as Bob Cochran, secretary of the Society of Paper Money Collectors, told us, errors are quite common in the printing process:

  The most common errors are in inking, cutting, and in the overprinting operation. With inking there can be too much, not enough, or unacceptable smears. Notes are printed in sheets of 32; the back is printed in all green ink and then the face is printed in all black ink. If one side or the other is not registered properly, the designs will not match up on both sides after the sheets are cut up; if the registration is very poor, the notes will be replaced. A third separate printing operation adds the serial number and Treasury Seal; the major error possibilities are in inking and placement, since the basic note design already exists at this point.

  You have probably noticed that serial numbers on U.S. currency are preceded by a letter. That letter designates which of the twelve Federal Reserve districts issued the note (this is why the letters span A through L). For example, all serial numbers preceded by D (the fourth letter of the alphabet) are issued by the Fourth District of the Federal Reserve (Cleveland). Here is a list of the twelve Federal Reserve Bank districts and the letter designations for each:

  District

  Letter

  City

  1

  A

  Boston

  2

  B

  New York

  3

  C

  Philadelphia

  4

  D

  Cleveland

  5

  E

  Richmond

  6

  F

  Atlanta

  7

  G

  Chicago

  8

  H

  St. Louis

  9

  I

  Minneapolis

  10

  J

  Kansas City

  11

  K

  Dallas

  12

  L

  San Francisco

  The star note enables the treasury to issue a new set of serial numbers rather than attempting to reassign all the missing serial numbers of defective notes. On U.S. notes, a star substitutes for the prefix letter. A replacement U.S. note might look like this: 00000007 B. On Federal Reserve notes, a star substitutes for the letter at the end of the serial number, so that the location of the Federal
Reserve district is kept intact: D 00000007 .

  William Bischoff, associate curator of the American Numismatic Society, adds that there is one other use for the star note. The Bureau of Printing and Engraving uses printers with eight-digit numbering cylinders to produce one hundred million notes at a time. But for the one-hundred-millionth note, a ninth digit is needed. Rather than bothering to add another digit on the cylinder that would literally be used on one out of a hundred million notes, the one-hundred-millionth note is a hand-inserted star note.

  To What Do the Numbers Assigned to Automotive Oil Refer?

  Thirty years ago, 10-30 was considered a premium automotive oil. Today, one can buy 10-50 or even 10-60 oil, but few people know what these numbers mean.

  The numbers measure the viscosity of the oil. The higher the number, the higher the viscosity (meaning the oil is less likely to flow). Although the viscosity of a liquid is not always directly correlated to thickness, high-viscosity oils are thicker than their low-viscosity counterparts.

  The numbers on engine and transmission oils are assigned by the Society of Automotive Engineers. Their numbers range from 5W to 60. The W stands for winter. When a W follows a number, it indicates the viscosity of the oil at a low temperature. When there is no W following a number, the viscosity is measured at a high temperature.

  All oil companies promote multigrade oils, which are designed to perform well in hot or cold temperatures. Thus 10W-40 doesn’t indicate a range of viscosity, but rather the low viscosity of oil during winter (when one desires greater flow capabilities) and high viscosity in the summer.

  Submitted by Tom and Marcia Bova of Rochester, New York.

  When I Put One Slice of Bread in My Toaster, the Heating Element in the Adjacent Slot Heats Up as Well. So Why Does My Toaster Specify Which Slot to Place the Bread in If I Am Toasting Only One Slice?

  Considering that the pop-up toaster has proven to be perhaps the most durable and dependable kitchen appliance, we were surprised to learn that toasting technology varies considerably from model to model. The earliest toasters browned one side of bread at a time; one had to decide when to flip the bread over by hand, a problem not unlike the momentous decision of when to flip over a frying pancake or hamburger.

  Now that even the simplest pop-up toaster has a toast selector dial to allow the user to choose the preferred degree of doneness, most of the guesswork in toasting has been eliminated. We are not even allowed to select which of two or four slots to put in our one meager slice of bread. Why not?

  Actually, nothing dire will result if you don’t use the slot marked ONE SLICE. The worst that will happen is that the toaster will pop up an underdone or overdone piece. But why is the same well that manages to produce wonderful toast when it has company next door suddenly rendered incompetent when forced to work alone?

  The answer depends upon the type of technology the toaster uses to determine doneness. The simplest toasters, now passé, worked from a simple time principle. The darker the brownness dial was set for, the longer the timer set for the toaster to heat the bread. Toasters that worked on a timer alone did not need a ONE SLICE notation because they always cooked the bread for the same amount of time, as long as the brownness dial wasn’t changed. Using a timer alone guaranteed that a second set of toast would come out overdone, because the toaster was already warmed up yet toasted the second set for the same period of time as the first batch that was heated from a “cold start.”

  To solve the problem, appliancemakers inserted a thermostatic switch in toasters, which measured the heat of the toaster rather than the time elapsed in cooking. The thermostat alone caused a reverse problem. A second batch of bread would come out underdone because the first cycle had already caused the heating element to charge. The toaster didn’t “know” that the second batch of bread hadn’t been exposed to the toaster long enough; it knew only that the toaster had achieved the desired temperature.

  The solution to the problem was to use a combination timer-thermostat. Today, the timer is not set off until the thermostat tells the timer that the toaster has reached the preset temperature (determined by the setting of the brownness dial). With this technology, it might take a minute for the thermostat to tell the timer to start ticking with the first set of toast but only a few seconds for the second or third.

  We spoke to an engineer at Proctor-Silex who told us that most of their toasters have the thermostat close to—or in some cases, inside—the well that is marked ONE SLICE so the thermostat can do a more accurate job of “reading” the correct temperature for that slice. Some toasters that have ONE SLICE markings are “energy saver” toasters, specifically designed so that the heating element in the second slot will not be charged if it does not contain bread.

  Sunbeam has long produced the 20030 toaster, an elegant two-slicer that selects the proper brownness of the bread by a radiant control that “reads” the surface of the bread to determine the degree of doneness. As far as we know, the Sunbeam 20030 is the only toaster that doesn’t work on a time principle. The 20030 actually measures the surface temperature of the bread by determining its moisture level and can accurately measure the time needed to toast any type of bread. Wayne R. Smith, of Sunbeam Public Relations, told Imponderables, “There’s no point in having radiant controls in both slots when having a control in one slot works just as well.”

  Submitted by Lisa M. Giordano of Tenafly, New Jersey. Thanks also to Muriel S. Marschke of Katonah, New York; and Jim Francis of Seattle, Washington.

  Why Are Almost All Cameras Black?

  Black isn’t the most obvious color we would pick for cameras. Not only is black an austere and a threateningly high-tech color to amateurs, it would seem to have a practical disadvantage. As Jim Zuckerman, of Associated Photographers International, explained, black tends to absorb heat more than lighter colors, and heat is the enemy of film.

  Of course, there was and is no reason why the exteriors of cameras need to be black. For a while, chromium finishes were popular on 35 millimeter cameras, but professional photographers put black tape over the finish to kill any possible reflections. Sure, some companies now market inexpensive cameras with decorator colors on the exterior. Truth be told, the persistence of black exteriors on cameras has more to do with marketing than anything else. As Tom Dufficy, of the National Association of Photographic Manufacturers, told us: “To the public, black equals professional.”

  Submitted by Herbert Kraut of Forest Hills, New York.

  Why Is There a Permanent Press Setting on Irons?

  We buy a permanent press shirt so that we won’t have to iron it. Then after we wash the shirt for the first time, it comes out of the dryer with wrinkles. Disgusted, we pull out our iron only to find that it has a permanent-press setting. Are iron manufacturers bribing clothiers to renege on their promises? Is this a Communist plot?

  The appliance industry is evidently willing to acknowledge what the clothing industry is reluctant to admit: A garment is usually permanently pressed only until you’ve worn it—once. Wayne R.Smith, consultant in Public Relations to the Sunbeam Appliance Company, suggested that “permanent press” was chosen to describe the benefits of some synthetic materials because “it has a far more attractive sound to consumers than ‘wrinkle-resistant.’”

  We know what Mr. Smith means. We’ve always felt that the difference between a water-resistant watch and a waterproof watch was that the waterproof one would die the moment after it hit H2O.

  What Causes Double-Yolk Eggs? Why Do Egg Yolks Sometimes Have Red Spots on Them?

  Female chicks are born with a fully formed ovary containing several thousand tiny ova, which form in a cluster like grapes. A follicle-stimulating hormone in the bloodstream develops these ova, which will eventually become egg yolks. When the ova are ripe, the follicle ruptures and an ovum is released. Usually when a chicken ovulates, one yolk at a time is released and travels down the oviduct, where it will acquire a surrounding white membrane and shell.

>   But occasionally two yolks are released at the same time. Double-yolk eggs are no more planned than human twins. But some chickens are more likely to lay double-yolk eggs. Very young and very old chickens are most likely to lay double yolks; young ones because they don’t have their laying cycles synchronized, and old ones because, generally speaking, the older the chicken, the larger the egg she will lay. And for some reason, extra-large and jumbo eggs are most subject to double yolks.

  If a chicken is startled during egg formation, small blood vessels in the wall may rupture, producing in the yolk blood spots—tiny flecks of blood. Most eggs with blood spots are removed when eggs are graded, although they are perfectly safe to eat.

  Submitted by Lewis Conn of San Jose, California. Thanks also to Melody L. Love of Denver, North Carolina.

  Why Are Barns Red?

  We first encountered this Imponderable when a listener of Jim Eason’s marvelous KGO-San Francisco radio show posed it. “Ummmmm,” we stuttered.

  Soon we were bombarded with theories. One caller insisted that red absorbed heat well, certainly an advantage when barns had no heating system. Talk-show host and guest agreed it made some sense, but didn’t quite buy it. Wouldn’t other colors absorb more heat? Why didn’t they paint barns black instead?