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  Now the bad news. In practice, most of the time, “dissolving” the stain translates into spreading the stain. Usually, hot water helps break up the stain, but it doesn’t lift the stain; rather, it allows stains to penetrate deeper into the fiber. Oily stains, especially on synthetics, have this reaction. Once the stain sets deeply enough in a fabric, detergents or dry cleaning are often ineffective.

  In other cases, hot water can actually create a chemical change in the stain itself that hampers removal. Protein stains are a good example of this problem, as Lever Brothers spokesperson Sheryl Zapcic illustrates:

  One common type of stain that can be set by hot water is a protein stain. If protein is a component of the stain, rinsing with hot water will coagulate the protein. For example, egg white, which is a protein, can be loosened with cold water without coagulating; however, hot water will immediately coagulate the egg white. Technically, this is called denaturation of the protein. In any event, the stain becomes insoluble or set.

  On some stains, it won’t matter much whether hot or cold water is used.

  Our own rule of thumb on this subject is: Nothing works. We have been in fancy French restaurants where our dining companions insist that “only club soda can get that stain out of your tie.” Of course, we never have club soda at hand. To placate our true believer, we end up ordering a glass. And, naturellement, the stain lingers as an enduring testament to our naïve belief that we will one day get a stain out of a garment successfully.

  Submitted by Pamela Gibson of Kendall Park, New Jersey.

  * * *

  HOW ARE THE FIRST DAYS OF WINTER AND SUMMER CHOSEN?

  * * *

  This Imponderable was posed by a caller on John Dayle’s radio show in Cleveland, Ohio. John and the supposed Master of Imponderability looked at each other with blank expressions. Neither one of us had the slightest idea what the answer was. What did it signify?

  We received a wonderful answer from Jeff Kanipe, an associate editor at Astronomy. His answer is complicated but clear, clearer than we could rephrase. So Jeff generously has consented to let us quote him in full:

  The first day of winter and summer depend on when the sun reaches its greatest angular distance north and south of the celestial equator.

  Imagine for a moment that the Earth is reduced to a tiny ball floating in the middle of a transparent sphere and that we’re on the “outside” looking in. This sphere, upon which the stars seem fixed and around which the moon, planets, and sun seem to move, is called the celestial sphere. If we simply extend the earth’s equator to the celestial sphere it forms a great circle in the sky: the celestial equator.

  Now imagine that you’re back on the Earth looking out toward the celestial sphere. You can almost visualize the celestial equator against the sky. It forms a great arc that rises above the eastern horizon, extends above the southern horizon, and bends back down to the western horizon.

  But the sun doesn’t move along the celestial equator. If it did, we’d have one eternal season. Rather, the seasons are caused because the Earth’s pole is tilted slightly over 23 degrees from the “straight up” position in the plane of the solar system. Thus, for several months, one hemisphere tilts toward the sun while the other tilts away. The sun’s apparent annual path in the sky forms yet another great circle in the sky called the ecliptic, which, not surprisingly, is inclined a little over 23 degrees to the celestial equator.

  Motions in the solar system run like clockwork. Astronomers can easily predict (to the minute and second!) when the sun will reach its greatest angular distance north of the celestial equator. This day usually occurs about June 21. If you live in the Northern Hemisphere and note the sun’s position at noon on this day, you’ll see that it’s very high in the sky because it’s as far north as it will go. The days are longer and the nights are shorter in the Northern Hemisphere. The sun is thus higher in the sky with respect to our horizon, and remains above the horizon for a longer period than it does during the winter months. Conditions are reversed in the Southern Hemisphere: short days, long nights. It’s winter there.

  Just reverse the conditions on December 22. In the Northern Hemisphere, the sun has moved as far south as it will go. The days are short, while the lucky folks in the Southern Hemisphere are basking in the long, hot, sunny days.

  The first days of spring and fall mark the vernal and autumnal equinox, when the sun crosses the equator traveling north and south. As astronomer Alan M. MacRobert points out, the seasonal divisions are rather arbitrary:

  Because climate conditions change continuously, there is no real reason to have four seasons instead of some other number. Some cultures recognize three: winter, growing, and harvest. When I lived in northern Vermont, people spoke of six: winter, mud, spring, summer, fall, and freezeup.

  * * *

  WHY DO ASTRONOMERS LOOK AT THE

  SKY UPSIDE DOWN AND REVERSED?

  WOULDN’T IT BE POSSIBLE TO REARRANGE

  THE MIRRORS ON TELESCOPES?

  * * *

  Merry Wooten, of the Astronomical League, informs us that most early telescopes didn’t yield upside-down images. Galileo’s original spyglass used a negative lens as an eyepiece, just as cheap field glasses made with plastic lenses do now. So why do unsophisticated binoculars yield the “proper” image and expensive astronomical telescopes render an “incorrect” one?

  Astronomy editor Jeff Kanipe explains:

  The curved light-gathering lens of a telescope bends, or refracts, the light to focus so that light rays that pass through the top of the lens are bent toward the bottom and rays that pass through the bottom of the lens are bent toward the top. The image thus forms upside down and reversed at the focal point, where an eyepiece enlarges the inverted and reversed image.

  Alan MacRobert, of Sky & Telescope magazine, adds that some telescopes turn the image upside down, and others also mirror-reverse it: “An upside-down ‘correct’ image can be viewed correctly just by inverting your head. But a mirror image does not become correct no matter how you may twist and turn to look at it.”

  OK. Fine. We could understand why astronomers live with inverted and upside-down images if they had to, but they don’t.

  Terrestrial telescopes do rearrange their image. Merry Wooten says that terrestrial telescopes can correct their image by using porro prisms, roof prisms, or most frequently, an erector lens assembly, which is placed in front of the eyepiece to create an erect image.

  Why don’t astronomical telescopes use erector lenses? For the answer, we return to Jeff Kanipe:

  Most astronomical objects are very faint, which is why telescopes with larger apertures are constantly being proposed: Large lenses and mirrors gather more light than small ones. Astronomers need every scrap of light they can get, and it is for this reason that the image orientation of astronomical telescopes are not corrected. Each glass surface the light ray encounters reflects or absorbs about four percent of the total incoming light. Thus if the light ray encounters four glass components, about sixteen percent of the light is lost. This is a significant amount when you’re talking about gathering the precious photons of objects that are thousands of times fainter than the human eye can detect. Introducing an erector into the optical system, though it would terrestrially orient the image, would waste light. We can afford to be wasteful when looking at bright objects on the earth but not at distant, faint galaxies in the universe.

  And even if the lost light and added expense of erector prisms weren’t a factor, every astronomer we contacted was quick to mention an important point: There IS no up or down in outer space.

  Submitted by William DeBuvitz of Bernardsville, New Jersey.

  * * *

  WHY DOES GREASE TURN

  WHITE WHEN IT COOLS?

  * * *

  You finish frying some chicken. You reach for the used coffee can to discard the hot oil. You open the lid of the coffee can and the congealed grease is thick, not thin, and not the yellowish-gold color of the
frying oil you put in before, but whitish, the color of glazed doughnut frosting. Why is the fat more transparent when it is an oil than when it is grease?

  When the oil cools, it changes its physical state, just as transparent water changes into more opaque ice when it freezes. Bill DeBuvitz, a longtime Imponderables reader and, more to the point, an associate professor of physics at Middlesex County College in New Jersey, explains:

  When the grease cools, it changes from a liquid to a solid. Because of its molecular structure, it cannot quite form a crystalline structure.

  Instead, it forms “amorphous regions” and “partial crystals.” These irregular areas scatter white light and make the grease appear cloudy.

  If grease were to solidify into a pure crystal, it would be much clearer, maybe like glass. Incidentally, paraffins like candle wax behave just like grease: They are clear in the liquid form and cloudy in the solid form.

  Submitted by Eric Schmidt of Fairview Park, Ohio.

  * * *

  WHY DOES MENTHOL FEEL COOL TO

  THE TASTE AND COOL TO THE SKIN?

  * * *

  Of course, the temperature of menthol shaving cream isn’t any lower than that of musk shaving cream. So clearly, something funny is going on. R. J. Reynolds’s public relations representative, Mary Ann Usrey, explains the physiological shenanigans:

  The interior of the mouth contains many thermoreceptors that respond to cooling. These thermoreceptors may be compared to the receptors for the sensations of “sweet,” “salty,” “bitter,” etc.

  In other words, individual receptors respond to specific types of stimulation. For example, a person’s perception that sugar is sweet is initiated when the receptors in the mouth for “sweet” are stimulated. Menthol feels cool to the taste because menthol stimulates the thermoreceptors that respond normally to cooling.

  Menthol has the ability to “trick” those thermoreceptors into responding. The brain receives the message that what is being experienced is “cool.”

  Although not as easy to stimulate by menthol as those in the mouth, the skin also contains those types of thermoreceptors, which is why menthol shaving cream or shaving lotion feels cool to the skin.

  Submitted by Allan J. Wilke of Cedar Rapids, Iowa.

  * * *

  WHY DOES HEAT LIGHTNING

  ALWAYS SEEM FAR AWAY? AND WHY DON’T

  YOU EVER HEAR THUNDER DURING

  HEAT LIGHTNING?

  * * *

  Heat lightning is actually distant lightning produced by an electrical storm too far away to be seen by the observer. What you see is actually the diffused reflection of the distant lightning on clouds.

  You don’t hear thunder because the actual lightning is too far away from you for the sound to be audible. There is thunder where the lightning is actually occurring.

  * * *

  WHEN GLASS BREAKS, WHY DON’T THE

  PIECES FIT BACK TOGETHER PERFECTLY?

  * * *

  We received a wonderful response to this Imponderable from Harold Blake, who you might remember from When Do Fish Sleep? as the gentleman who spent some time in college simulating the aroma of Juicy Fruit gum. It’s nice to know that Mr. Blake, now a retired engineer, is still trying to find the solutions to the important things in life.

  The key point Blake makes about this Imponderable is to remember that while glass appears to be inflexible, it does bend and change shape. If you throw a ball through a plate glass window, the glass will try to accommodate the force thrust upon it; it will bend. But if bent beyond its limits, glass shatters or ruptures.

  At the point that the glass breaks, the glass’s shape is distorted but the break is a perfect fracture—the parts would fit back together again. But as soon as the glass shatters, the parts begin to minimize their distortion and return to the unstressed state.

  When the pieces return to their unstressed state, the fracture is no longer “perfect.” Like a human relationship, things are never quite the same after a breakup.

  Blake points out that other seemingly inflexible materials show the same tendencies as glass. Ceramics, pottery, and metals, for example, also distort and then return to a slightly altered “original” configuration.

  Submitted by Charles Venezia of Iselin, New Jersey.

  * * *

  WHY DOES WOOD “POP” WHEN

  PUT ON A FIRE?

  * * *

  John A. Pitcher, director of the Hardwood Research Council, was kind enough to tackle this burning Imponderable:

  Wood pops when put on a fire because there are little pockets of sap, pitch [resin], or other volatiles that are contained in the wood. As the wood surface is heated and burns, heat is transferred to the sap or pitch deeper in the wood.

  The sap or pitch first liquefies, then vaporizes as the temperature increases. Gasses expand rapidly when heated and put tremendous pressure on the walls of the pitch pocket. When the pressure gets high enough, the pocket walls burst and the characteristic sound is heard.

  Submitted by Patric Conroy of Walnut Creek, California.

  * * *

  WHY DOES A FIRE CREATE A CRACKLING

  SOUND? IS THERE ANY REASON WHY A FIRE

  CRACKS MOST WHEN FIRST LIT?

  * * *

  Of course, “pops” are not unrelated to “crackles.” John Pitcher explains that the larger the sap or pitch pockets in the wood, the bigger the pop; but if there are smaller but more numerous pockets, the wood will crackle instead.

  The reason fires crackle most when first lit is that the smaller pieces of wood, used as kindling, heat up quickly. The inside sap pockets are penetrated and crackle immediately. Big pieces of wood burn much more slowly, with fewer, intermittent, but louder pops.

  For those of you who are, pardon the expression, “would-be” connoisseurs of lumber acoustics, Pitcher provided Imponderables readers with a consumer’s guide:

  There are distinct differences in the popping characteristics of woods. High on the list of poppers is tamarack or larch. Most conifers are ready poppers. On the other hand, hardwoods, such as ash, elm, and oak, tend to burn quietly, with only an occasional tastefully subdued pop. You might call them poopers rather than poppers.

  Submitted by Andrew F. Garruto of Kinnelon, New Jersey.

  * * *

  WHO DECIDES WHERE THE BOUNDARY LINE IS BETWEEN OCEANS? IF YOU’RE ON THE OCEAN, HOW DO YOU KNOW WHERE THAT LINE IS?

  * * *

  Much to our shock, there really is a “who.” The International Hydrographic Organization (IHO) is composed of about seventy member countries, exclusively nations that border an ocean (eat your heart out, Switzerland!). Part of their charter is to assure the greatest possible uniformity in nautical charts and documents, including determining the official, standardized ocean boundaries.

  All of the oceans of the world are connected to one another—you could theoretically row from the Indian Ocean to the Arctic Ocean (but, boy, would your arms be tired). No one would dispute the borders of the oceans that hit a landmass, but what about the 71 percent of the earth that is covered by sea?

  The IHO issues a publication, “Limits of Oceans and Seas,” that determines exactly where these water borders are located, but is used more by researchers than sailors. Michel Huet, chief engineer at the International Hydrographic Bureau, the central office of the IHO, wrote to Imponderables and quoted “Limits of Oceans and Seas”:

  “The limits proposed…have been drawn up solely for the convenience of National Hydrographic Offices when compiling their Sailing Directions, Notices to Mariners, etc., so as to ensure that all such publications headed with the name of an ocean or sea will deal with the same area, and they are not to be regarded as representing the result of full geographic study; the bathymetric [depth measurements of the ocean floor] results of various oceanographic expeditions have, however, been taken into consideration so far as possible, and it is therefore hoped that these delimitations will also prove acceptable to oceanographers. Th
ese limits have no political significance whatsoever.” Therefore, the boundaries are established by common usage and technical considerations as agreed to by the Member States of the IHO.

  Essentially, a committee of maritime nations determines the borders and titles for the oceans.

  How would the IHO decide on the border between the Atlantic and Pacific? A somewhat arbitrary man-drawn line was agreed upon that extends from Cape Horn, on the southern tip of South America, across the Drake Passage to Antarctica. A specific longitude was chosen, so the border goes exactly north-south from the cape to Antarctica.

  Of course, there are no YOU ARE LEAVING THE PACIFIC OCEAN, WELCOME TO THE ATLANTIC OCEAN signs posted along the longitude. But a sailor with decent navigational equipment could determine which ocean he was in—likewise with the boundaries between other oceans.

  Unlike the United Nations, most of the time the IHO does not become embroiled in political disputes, presumably because the precise location of the oceans’ borders has no commercial or military implications. Disputes are not unheard of, though. For example, Korea and Japan recently tussled about the designation of the sea that divides their countries. Traditionally, the body of water has been called the Sea of Japan, but Korea wanted it changed to “East Sea.”