It sounds like a case of poor surgery to me. You treated the patient (the soil) badly by pounding the wound that you made in the first place.
3. Soil often dries during the digging/handling/moving. Grant reports that the water in soil sometimes causes the soil to take up more space than it does when dry.
Both of our experts stressed that the scenario outlined by our correspondent is not always true. Sometimes, you may have leftover soil after refilling, as Dr. Hole explains:
It is risky to say that “you never have enough soil to refill.” Because sometimes you have too much soil. If you saved all your diggings on a canvas and put it all back, there could be so much soil that it would mound up, looking like a brown morning coffee cake where the hole had been.
…you loosened the soil a lot when you dug it out. When you put the soil back, there were lots of gaps and pore spaces that weren’t there before. It might take a year for the soil to settle back into its former state of togetherness. A steady, light rain might speed the process a little bit.
Submitted by Loren A. Larson of Orlando, Florida.
* * *
WHY IS IT THAT WHAT LOOKS TO US
LIKE A HALF-MOON IS CALLED A
QUARTER-MOON BY ASTRONOMERS?
* * *
An intriguing Imponderable, we thought, at least until Robert Burnham, editor of Astronomy, batted it away with the comment, “Aw, c’mon, you picked an easy one this time!”
Much to our surprise, when astronomers throw lunar fractions around, they are referring to the orbiting cycle of the Moon, not its appearance to us. Sky & Telescope’s associate editor, Alan M. MacRobert, explains:
The Moon is half lit when it is a quarter of the way around its orbit. The count begins when the Moon is in the vicinity of the Sun (at “new Moon” phase). “First quarter” is when the Moon has traveled one-quarter of the way around the sky from there. The Moon is full when it is halfway around the sky, and at “third quarter” or “last quarter” when it’s three-quarters of the way around its orbit.
Robert Burnham adds that “quarter-Moons” and “half-Moons” aren’t the only commonly misnamed lunar apparitions. Laymen often call the crescent moon hanging low in the evening sky a “New Moon,” but Burnham points out that at this point, the moon is far from new: “In fact, by then the crescent Moon is some three or four days past the actual moment of New Moon, which is the instant when the center of the Moon passes between the Earth and Sun.”
Submitted by Susan Peters of Escondido, California.
Thanks to Gil Gross, of New York, New York.
* * *
WHAT PRECISELY IS SEA LEVEL? AND HOW DO
THEY DETERMINE EXACTLY WHAT IT IS?
* * *
Painstakingly. Obviously, the sea level in any particular location is constantly changing. If you measure the ocean during low tide and then high tide, you won’t come up with the same figure. Wind and barometric shifts also affect the elevation of the seas.
But the oceans are joined and their height variation is slight. So geodesists (mathematicians who specialize in the study of measurement) and oceanographers settle for an approximation. Because the cliché that “water seeks its own level” is true, geodesists worry more about sea level variations over time than between places. Measurements are taken all over the globe; there is no one place where sea level is determined. One sea level fits all.
The National Geodetic Survey defines “mean sea level” as the “average location of the interface between ocean and atmosphere, over a period of time sufficiently long so that all random and periodic variations of short duration average to zero.” The U.S. National Ocean Service has set 19 as the appropriate number of years to sample sea levels to eliminate such variations; in some cases, measurements are taken on an hourly basis. Geodesists simply add up the 19 years of samples and divide by 19 to arrive at the mean sea level.
The mean sea level has been rising throughout most of the twentieth century—on average, over a millimeter a year. On a few occasions, sea level has risen as much as five or six millimeters in a year, not exactly causing flood conditions, but enough to indicate that the rise was caused by melting of glaciers. If theories of the greenhouse effect and global warming are true, the rise of the global sea level in the future will be more than the proverbial drop in the bucket.
Submitted by Janice Brown of Albany, Oregon.
Thanks also to Wendy Neuman of Plaistow, New Hampshire;
Noel Ludwig of Littleton, Colorado; Jay Howard Horne of Pittsburgh,
Pennsylvania; Charles F. Longaker of Mentor, Ohio;
and Mrs. Violet Wright of Hobbes, New Mexico.
* * *
WHY DO PEANUTS IN THE SHELL
USUALLY GROW IN PAIRS?
* * *
Botany 101. A peanut is not a nut but a legume, closer biologically to a pea or a bean than a walnut or pecan. Each ovary of the plant usually releases one seed per pod, and all normal shells contain more than one ovary.
But not all peanut shells contain two seeds. We are most familiar with Virginia peanuts, which usually contain two but occasionally sprout mutants that feature one, three, or four. Valencia and Spanish peanuts boast three to five seeds per shell.
Traditionally, breeders have chosen to develop two-seeded pods for a practical reason: Two-seeders are much easier to shell. According to Charles Simpson, of Texas A & M’s Texas Agricultural Experiment Station, there is little taste difference among the varieties of peanuts, but the three-seed peanuts are quite difficult to shell, requiring tremendous pressure to open without damaging the legume. We do know that patrons of baseball games wouldn’t abide the lack of immediate gratification. They’d much rather plop two peanuts than three into their mouths, at least if it means less toil and more beer consumption.
Submitted by Thad Seaver, A Company, 127 FSB.
* * *
DOES THE MOON HAVE ANY EFFECT
ON LAKES OR PONDS? IF NOT, WHY DOES IT
ONLY SEEM TO AFFECT OCEANS’ TIDES?
WHY DON’T LAKES HAVE TIDES?
* * *
If there is any radio show that we fear appearing on, it’s Ira Fistel’s radio show in Los Angeles. Fistel, a lawyer by training, has an encyclopedic knowledge of history, railroad lore, sports, radio, and just about every other subject his audience questions him about, and is as likely as we are to answer an Imponderable from a caller. Fistel can make a Jeopardy! Tournament of Champions winner look like a know-nothing.
So when we received this Imponderable on his show and we proceeded to stare at each other and shrug our shoulders (not particularly compelling radio, we might add), we knew this was a true Imponderable. We vowed to find an answer for the next book (and then go back on Fistel’s show and gloat about it).
Robert Burnham, senior editor of Astronomy, was generous enough to send a fascinating explanation:
Even the biggest lakes are too small to have tides. Ponds or lakes (even large ones like the Great Lakes) have no tides because these bodies of water are raised all at once, along with the land underneath the lake, by the gravitational pull of the Moon. (The solid Earth swells a maximum of about eighteen inches under the Moon’s tidal pull, but the effect is imperceptible because we have nothing that isn’t also moving by which to gauge the uplift.)
In addition, ponds and lakes are not openly connected to a larger supply of water located elsewhere on the globe, which could supply extra water to them to make a tidal bulge. The seas, on the other hand, have tides because the water in them can flow freely throughout the world’s ocean basins….
On the side of Earth nearest the Moon, the Moon’s gravity pulls seawater away from the planet, thus raising a bulge called high tide. At the same time on the other side of the planet, the Moon’s gravity is pulling Earth away from the water, thus creating a second high-tide bulge.
Low tides occur in between because these are the regions from which water has drained to flow into the two high-tide bulges. (The Sun exer
ts a tidal effect of its own, but only 46 percent as strong as the Moon’s.)
Some landlocked portions of the ocean—the Mediterranean or the Baltic—can mimic the tideless behavior of a lake, although for different reasons. The Mediterranean Sea, for example, has a tidal range measuring just a couple of inches because it is a basin with only a small inlet (the Strait of Gibraltar) connecting it to the global ocean. The Gibraltar Strait is both narrow and shallow, which prevents the rapid twice-a-day flow of immense volumes of water necessary to create a pronounced tide. Thus the rise and fall of the tide in the Atlantic attempts to fill or drain the Med, but the tidal bulge always moves on before very much water can pour in or out past Gibraltar.
Alan MacRobert, of Sky & Telescope, summarizes that a body of water needs a large area to slosh around in before tidal effects are substantial, and he provides a simple analogy:
Imagine a tray full of dirt dotted with thimbles of water, representing a landmass with lakes. You could tilt it slightly and nothing much would happen. Now imagine a tray full of water—an ocean. If you tilted it just a little, water would sloop out over your hands.
Submitted by a caller on the Ira Fistel show,
KABC-AM, Los Angeles, California.
* * *
WHAT KIND OF CONTAINER HOLDS THE
RAIN MEASURED BY METEOROLOGISTS?
* * *
You can set a bucket outside in your backyard, let the precipitation accumulate, and measure the bucket with a ruler. But after a while the thought is likely to occur to you: How big is the container supposed to be? Sure, it will take more rain to fill an inch of a big bucket than a thin beaker, but then the larger circumference of the bucket will also trap more water. Hmmmm. This isn’t as simple as it first seemed.
It turns out that meteorologists don’t let this stuff worry them too much. They use many different devices to measure rainfall. Perhaps the most common is the eight-inch rain gauge, a simple metal cylinder with an eight-inch-diameter top. The water is funneled from the outside cylinder into a smaller inner gauge. The water in the inner gauge is measured by a calibrated wooden or metal stick (which can convert the contents of different-sized gauges into the “inches” we hear about in weather reports). By funneling the water into the narrow inner gauge, the vertical scale is expanded, allowing accurate reading of rainfall to the nearest hundredth of an inch.
Richard Williams, meteorologist for the National Weather Service, told Imponderables that most of his agency’s offices use another method: weighing rain in a bucket and using a mathematical formula to convert weight into hundredths.
Williams adds that in a third type of gauge, rainfall is not collected at all:
As it falls, each one-hundredth inch of precipitation fills a small metal “bucket.” The bucket fills, tips over, and then empties. Each fill/empty cycle triggers an electrical contact and the number of “tips” is charted to determine the rainfall. This is particularly useful in determining the rate of rainfall and in making a permanent chart of the event.
Other variables affect accurate measurement of rainfall. But the most important problem is wind. Ground-level gauges will collect more rain, and tend to be more accurate, than those aboveground, especially if accompanied by an antisplash grid. If the rain gauge is set above the ground, high winds can create uneven distribution of rain and splashing of water onto, rather than into, the gauge.
The problems in measuring rainfall are minor compared to measuring snowfall. Wind is a particular problem since blowing snow, rather than falling snow, might accumulate in gauges, particularly ground-level gauges. The temperature when the snow was formed, wind patterns, and how long the snow has been caught in the gauge may determine whether snow accumulates in air-filled, feathery layers or is compacted down to a tight, dense pack. Since the density of fallen snow varies tremendously, scientists require some way to compare snowfalls accumulated under different conditions.
Meteorologists use several techniques to deal with these problems:
1. Snow boards. These boards are put out on the ground. The accumulation is measured on an hourly basis and then cleaned off. This labor-intensive method assures a reading before the snow can pack down. But any one board might not be representative of an area, so many must be used if an accurate assessment of precipitation is important.
2. Weighing. Essentially the same technique we discussed with rain gauges. A heating element is put into a gauge (often a standard rain gauge) so that the snow melts. The water is then weighed and converted into “inches.”
3. Snow pillows. These immediately record the weight of the snow that accumulates above them without converting the snow into water.
Submitted by Ted Roter of Los Angeles, California.
Thanks also to Valerie M. Shields of Danville, California.
* * *
WHY ARE CITIES WARMER THAN
THEIR OUTLYING AREAS?
* * *
In almost every metropolitan area in the United States and Canada, the city is warmer than its immediately surrounding areas. Compared to suburban and rural areas, cities have gotten warmer throughout the twentieth century.
Do the cities themselves generate enough heat to raise the temperature measurably? Is there something about cities that allows them to retain heat? The answer to both questions: Yes.
The heat generated by buildings, factories, vehicles, lighting, and other by-products of modern technology is enough to raise the temperature a degree or two in densely populated cities. The hot air exhaled by air conditioners during summer months affects the temperature outside as surely, if less dramatically, as it affects the temperature inside an air-conditioned room.
But even if cities did not generate their own heat, they would still be warmer than rural or suburban areas. When the sun shines on the flat, featureless Kansas countryside, the light is reflected back to the sky. When the sun shines in midtown Manhattan, the light bounces from skyscraper to skyscraper like a manic Ping-Pong ball—more of the sun’s warmth lingers close to ground level than on the Kansan farm and more warmth is absorbed in the city. In fact, buildings and cement pavements can retain more heat and more sunlight than grass, trees, or the farmer’s topsoil.
Precipitation has a cooling effect in the country. Rain is stored in the ground and recycles itself through evaporation and plant respiration, thus absorbing heat. In the city, precipitation is funneled into sewers, effectively eliminating much of its cooling effect. The relative lack of this evaporation in the city explains why cities tend to be less humid than rural areas.
It is commonly assumed that air pollution is what makes cities warmer. Since dust particles can absorb radiation, the theory goes, the more polluted the city, the higher the temperature is artificially raised. There is only one problem with this hypothesis: Dust particles can also reflect radiation, bouncing rays that would otherwise be trapped near ground level back up to the sky. The jury is still out on the net effects of pollution on temperature.
One fact remains indisputable, though. On extremely windy days, the temperature differences between city and country tend to disappear; on calm days, there is more of a discrepancy than normal. The wind mitigates human intrusion upon the “natural” climate.
While modern life hasn’t seemed to affect wind patterns, we have already created a lifestyle that might permanently change our temperature patterns, at least in metropolitan areas. Meteorologists have little idea, at this point, if these barely perceptible changes (cities have become a few degrees warmer in the last fifty years or so) will create profound changes in our ecosystem. They might. And we could usher in the next Ice Age with our cities as hothouses.
* * *
WHY DO PEOPLE LOOK UP WHEN THINKING?
* * *
Medical doctors have a nasty habit. You pose them a particularly tough Imponderable and they answer, “I don’t know.” Most medical and scientific research is done on topics that seem likely to yield results that can actually help clinicians with everyda
y problems. Determining why people look up when thinking doesn’t seem to be a matter of earth-shattering priority.
Ironically, some serious psychologists have decided that this question is important, have found what they think is a solution to the Imponderable and, most amazingly, found a very practical application for this information. These psychologists are known as neurolinguists.
Neurolinguists believe that many of our problems in human interaction stem from listeners not understanding the frame of reference of the people speaking to them. Neurolinguists have found that most people tend to view life largely through one dominant sense—usually sight, hearing, or touching. There are many clues to the sensory orientation of a person, the most obvious being his or her choice of words in explaining thoughts and feelings. Two people with varying sensory orientations might use totally different verbs, adjectives, and adverbs to describe exactly the same meaning. For example, a hearing-oriented person might say, “I hear what you’re saying, but I don’t like the sound of your voice.” The visually oriented person might say, “I see what you mean, but I think your real attitude is crystal clear.” The touch-dominant person (neurolinguists call them kinesthetics) would be more likely to say, “I feel good about what you are saying, but your words seem out of touch with your real attitude.”
Science Page 7
