When Do Fish Sleep? (4 page)
Submitted by Jack Belck of Lansing, Michigan.
How
Is the Caloric Value of Food Measured?
Imponderables
is on record as doubting the validity of caloric measurements. It defies belief that the caloric value of vegetables such as potato chips and onion rings, full of nutrients, could possibly be higher than greasy tuna fish or eggplant. Still, with an open mind, we sought to track down the answer to this Imponderable.
Calories are measured by an apparatus called a
calorimeter
. The piece of food to be measured is placed inside a chamber, sealed, and then ignited and burned. The energy released from the food heats water surrounding the chamber. By weighing the amount of water heated, noting the increase in the water’s temperature and multiplying the two, the energy capacity of the food can be measured. A calorie is nothing more than the measurement of the ability of a particular nutrient to raise the temperature of one gram of water one degree Centigrade. For example, if ten thousand grams of water (the equivalent of ten liters or ten thousand cubic centimeters) surrounding the chamber is 20 degrees Centigrade before combustion and then is measured at 25 degrees after combustion, the difference in temperature (five degrees) is multiplied by the volume of water (ten thousand grams) to arrive at the caloric value (fifty thousand calories of energy).
If fifty thousand calories sounds like too high a number to describe heating ten liters of water five degrees, your instincts are sound. One calorie is too small a unit of measurement to be of practical use, so the popular press uses “Calories,” really kilocalories, one thousand times as much energy as the lowercase “calorie.”
The calorimeter is a crude but reasonable model for how our body stores and burns energy sources. The calorimeter slightly overstates the number of calories our body can use from each foodstuff. In the calorimeter, foods burn completely, with only some ashes (containing minerals) left in the chamber. In our body, small portions of food are indigestible, and are excreted before they break down to provide energy. The rules of thumb are that two percent of fat, five percent of carbohydrates, and eight percent of proteins will not be converted to energy by the body.
Food scientists have long known the caloric count for each food group. One gram of fat contains more than twice the number of calories (nine).
Scientists can easily ascertain the proportion of fat to carbohydrates or proteins, so it might seem that calories could be measured simply by weighing the food. When a food consists exclusively of proteins and carbohydrates, for example, one could simply multiply the weight of the food by four to discover the calorie count.
But complications arise. Certain ingredients in natural or processed foods contain no caloric value whatsoever, such as water, fiber, and minerals. Foods that contain a mixture, say, of water (zero calories), fiber (zero calories), proteins (four calories per gram), fats (nine calories per gram), and carbohydrates (four calories per gram), along with some trace minerals (zero calories), are simply harder to calculate with a scale than a calorimeter.
Submitted by Jill Palmer of Leverett, Massachusetts
.
Who
Put E on Top of the Eye Chart? And Why?
Professor Hermann Snellen, a Dutch professor of ophthalmology, put the E on top of the eye chart in 1862. Although his very first chart was headed by an A, Snellen quickly composed another chart with E on top.
Snellen succeeded Dr. Frans Cornelis Donders as the director of the Netherlands Hospital for Eye Patients. Donders was then the world’s foremost authority on geometric optics. Snellen was trying to standardize a test to diagnose visual acuity, to measure how small an image an eye can accept while still detecting the detail of that image. Dr. Donders’ complicated formulas were based on three parallel lines; of all the letters of the alphabet, the capital E most closely resembled the lines that Dr. Donders had studied so intensively. Because Donders had earlier determined how the eye perceives the E, Snellen based much of his mathematical work on the fifth letter.
The three horizontal limbs of the E are separated by an equal amount of white space. In Snellen’s original chart, there was a one-to-one ratio between the height and width of the letters, and the gaps and bars were all the same length (in some modern eye charts, the middle bar is shorter).
Louanne Gould, of Cambridge Instruments, says that the E, unlike more open letters like L or U, forces the observer to distinguish between white and black, an important consitituent of good vision. Without this ability, E’s begin to like B’s, F’s, P’s or many other letters.
Of course, Snellen couldn’t make an eye chart full of only E’s, or else all his patients would have 20-10 vision. But Snellen realized that it was important to use the same letters many times on the eye charts, to insure that the failure of an observer to identify a letter was based on a visual problem rather than the relative difficulty of a set of letters. Ian Bailey, professor of optometry and director of the Low Vision Clinic at the University of California at Berkeley, says that it isn’t so important whether an eye chart uses the easiest or most difficult letters. Most eye charts incorporate only ten different letters, ones that have the smallest range of difficulty.
Today, many eye charts do not start with an E—and there is no technical reason why they have to—but most still do. Dr. Stephen C. Miller, of the American Optometric Association, suggests that the desire of optical companies to have a standardized approach to the production of eye charts probably accounts for the preponderance of E charts. And we’re happy about it. It’s a nice feeling to know that even if our vision is failing us miserably, we’ll always get the top row right.
Submitted by Merry Phillips of Menlo Park, California.
As soon as law enforcement officials descend upon a murder scene, a police photographer takes pictures of the corpse, making certain that the deceased’s position is established by the photographs. The medical examiner usually wants the body as soon as possible after the murder; the sooner an autopsy is conducted, the more valuable the information the police are likely to obtain.
Right before the body is removed, the police do indeed make an outline of the position of the victim. More often than not the body is outlined in chalk, including a notation of whether the body was found in a prone or supine posture.
A police investigation of a murder can take a long time, too long to maintain the murder site as it appeared after the murder. Forensic specialists cannot rely on photographs alone. Often, the exact position of the victim can be of vital importance in an investigation. By making an outline, the police can return to the murder scene and take measurements which might quash or corroborate a new theory on the case. Outline drawings may also be used in the courtroom to explain wound locations, bullet trajectories, and blood trails.
Herbert H. Buzbee, of the International Association of Coroners and Medical Examiners, told
Imponderables
that chalk is not always used to make outlines. Stick-em paper or string are often used on carpets, for example, where chalk might be obscured by the fabric. Carl Harbaugh, of the International Chiefs of Police, says that many departments once experimented with spray paint to make outlines, but found that paint traces were occasionally found on the victim, confusing the forensic analysis.
The ideal outline ingredient would be one that would show up, stay put, and do no permanent damage to any surface. Unfortunately, no such ingredient exists. Chalk gets high marks for leaving no permanent markings, but is not easily visible on many surfaces. Tape and string (which has to be fastened with tape) have a tendency to mysteriously twist out of shape, especially if they get wet.
None of these flaws in the markers would matter if murder victims were considerate enough to die in sites convenient to the police. Harbaugh says that on a street or highway any kind of outline will do. But what good is a chalk outline on a bed covered with linens and blankets?
Submitted by Pat O’Conner of Forest Hills, New York
.
In most restaurants, potato skins are a waste product, served as the casing of a baked potato or not at all. So we assumed that restaurants that specialized in potato skins used the rest of the potato to make mashed potatoes, boiled potatoes, or soups.
Our assumption was correct, but our correspondent mentions that potato skins are often served in bars that do not serve potatoes in any other form. Is it cost-effective for these establishments to serve the skins and dump the potato filling?
Most restaurants that serve potato skins buy the skins
only
, usually in frozen form. Linda Smith, of the National Restaurant Association, sent us a list of the biggest suppliers of potato skins. Most of these companies, not at all coincidentally, also supply restaurants with pre-cut cottage fries, hash browns, and O’Brien potatoes, among others. Ore-Ida isn’t about to sell the skin and throw away the potato.
Anyone who has ever dissected a frog in biology class does not want to contemplate the idea of chefs picking apart an entire frog to get at its legs. Suffice it to say that restaurants buy only the legs of frogs. What suppliers of frogs’ legs do with the rest of the frog is too gruesome for even us to contemplate.
Submitted by Myrna S. Gordon of Scotch Plains, New Jersey. Thanks also to Sharon Michele Burke of Menlo Park, California
.
If
Water Is Heavier than Air, Why Do Clouds Stay Up in the Sky?
What makes you think that clouds aren’t dropping? They are. Constantly.
Luckily, cloud drops do not fall at the same velocity as a water balloon. In fact, cloud drops are downright sluggards: They drop at a measly 0.3 centimeters per second. And cloud drops are so tiny, about 0.01 centimeters in diameter, that their descent is not even noticeable to the human eye.
Submitted by Ronald C. Semone of Washington, D.C
.
