When Do Fish Sleep? (19 page)
Any situation that wakes us up just after or during the course of a dream will make the sleeper perceive that he or she has been dreaming profusely. Dr. Robert W. McCarley, the executive secretary of the Sleep Research Society, told
Imponderables
that women in advanced stages of pregnancy often report that they are dreaming more frequently. Dr. McCarley believes that the perceived increase in dreaming activity of pregnant women is prompted not by psychological factors but because their sleep is constantly interrupted by physical discomforts.
Well, who said life was fair? It turns out that this blatant discrimination occurs not because anyone wants to persecute punters particularly but for the convenience and accuracy of the scorekeepers. Jim Heffernan, director of Public Relations for the National Football League, explains:
Punts are measured from the line of scrimmage, which is defined point, and it sometimes is difficult to determine exactly where the punter contacts the ball. Field goals are measured from the point of the kick because that is the defined spot of contact.
Submitted by Dale A. Dimas of Cupertino, California
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How
Does a Gas Pump “Know” When to Shut Off When the Fuel Tank Is Full?
A sensing device, located about one inch from the end of the nozzle, does nothing while fuel is flowing into the gas tank, but is tripped as soon as fuel backs up into the nozzle. The sensing device tells the nozzle to shut off.
Because of the location of the sensing device and the relatively deep position of the nozzle, a gas tank is never totally filled unless the customer or attendant “tops off” the tank. Topping off tanks is now illegal in most states and is a dangerous practice anywhere.
Submitted by Stephen O. Addison, Jr. of Charlotte, North Carolina
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There are more than two hundred billion dollars in coins and currency in circulation today in the United States. Determining the necessary timing for the minting and printing of new monies is therefore far from a simple task.
Most of the demand for new money comes from banks. When a bank receives more checks to cash than it can comfortably accommodate with its cash on hand, the bank orders new money from one of the twelve Federal Reserve Banks. Of course, the bank doesn’t get the new money for free; it uses a special checkbook to order new cash. When a bank has excess cash, it can deposit money into an account at the Federal Reserve Bank to offset its withdrawals.
What happens when the Federal Reserve Bank itself runs out of coins or notes? It places an order with the U.S. Mint for new coins or the Bureau of Engraving and Printing for the new currency. So demand from individual banks, funneled through a larger “distributor”—a Federal Reserve Bank—is responsible for the decision to issue new currency.
The average life-span of a dollar bill is fifteen to eighteen months. Larger denominations tend to have a longer life because they are circulated less frequently. The perishability of paper notes is the second major factor in calculating the requirements for new currency. In 1983 alone, the twelve Federal Reserve Banks destroyed more than 4.4 billion notes, worth more than $36 billion. The constant retirement of defective bills explains why almost one out of every four notes the Federal Reserve Bank sends to local banks is a newly printed one.
Every time a Federal Reserve Bank receives currency from a local bank, it runs the notes through high-speed machines designed to detect unfit currency. The newest machines can inspect up to sixty thousand notes per hour, checking each bill for dirt by testing light reflectivity (the dirtier the note, the less light is reflected) and authenticity (each note is tested for magnetic qualities that are difficult for counterfeiters to duplicate).
Notes valued at $100 or less are destroyed by the local Federal Reserve Bank. Unfit bills used to be burned and processed into mulch (we kid you not), but they are now shredded and compressed into four-hundred-pound bales. Most of these bundles of booty are discarded at landfills. Federal Reserve notes in denominations of $500 or more are canceled with distinctive perforations and cut in half lengthwise. The local Federal Reserve Bank keeps the upper half of each note and sends the other half to the Department of Treasury in Washington, D.C. When the Treasury Department verifies the legitimacy of the notes, it destroys its halves and informs the district bank that it may destroy the upper halves.
Coins have a much longer life in circulation, but the Mint still produces more than 50 million coins a day (compared to “only” twenty million notes printed per day). A U.S. Mint official told us that shipping coins across country is not a trivial task logistically—five-hundred-thousand pennies, for example, are a tad bulky. Huge tractor-trailer trucks, up to 55 feet in length and 13 1/2 feet high, are used to transport coins from the Mint to Federal Reserve Banks. Dimes, quarters, and half dollars are transported by armored carriers.
The demand process for coins works the same way as for paper notes. Although the Mint has learned that seasonal peaks run true from year to year (the demand for coins goes up during prime shopping seasons, such as Christmas), the Mint yields to the demands of its constituent Federal Reserve Banks.
Submitted by Hugo Kahn of New York, New York
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What
Is the Purpose of that Piece of Skin Hanging from the Back of Our Throat?
No, Kassie Schwan’s illustration to the contrary, the purpose of that “hanging piece of skin” is not to present targets for cartoon characters caught inside other characters’ throats. Actually, that isn’t skin hanging down, it’s mucous membrane and muscle. And it has a name: the uvula.
The uvula is a sort of anatomical tollgate between the throat and the pharynx, the first part of the digestive tract. The uvula has a small but important role in controlling the inflow and outflow of food through the digestive system. Dr. William P. Jollie, chairman, Department of Anatomy, the Medical College of Virginia, explains: “The muscle of both the soft palate and the uvula elevates the roof of the mouth during swallowing so that food and liquid can pass from the mouth cavity into the pharynx.”
Dr. L.J.A. DiDio, of the Medical College of Ohio, adds that the uvula also helps prevent us from regurgitating our food during swallowing. Without the uvula, some of our food might enter the nasal cavity, with unpleasant consequences.
Submitted by Andy Garruto of Kinnelon, New Jersey
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Why
Don’t Birds Tip Over When They Sleep on a Telephone Wire?
A telephone wire, of course, is only a high-tech substitute for a tree branch. Most birds perch in trees and sleep without fear of falling even during extremely windy conditions.
The secret to birds’ built-in security system is their specialized tendons that control their toes. The tendons are located in front of the knee joint and behind the ankle joint. As it sits on its perch, the bird’s weight stretches the tendons so that the toes flex, move forward, and lock around the perch.
Other tendons, located under the toe bones, guarantee that a sleeping bird doesn’t accidentally tip over. On the bottom of each tendon are hundreds of little projections. These fit perfectly into other ratchetlike sheaths. The body weight of the bird pressing against the telephone wire (or tree branch) guarantees that the projections will stay tightly locked within the sheaths.
Barbara Linton, of the National Audubon Society, adds that while this mechanism is most highly developed in perching birds and songbirds, many other birds do not perch to sleep. They snooze on the ground or while floating on water.
Submitted by Dr. Lou Hardy of Salem, Oregon. Thanks also to Jann Mitchell of Portland, Oregon
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Why
Is It Sometimes Necessary to Stroke a Fluorescent Lamp to Get It to Light?
All fluorescent bulbs require a ground plane to start. If the fluorescent lamp is inside a metal fixture, any piece of metal, such as the reflector, can serve as a ground plane. Richard H. Dowhan, manager of Public Affairs for GTE Products Corporation, told
Imponderables
that the closer the ground plane is to the tube, the easier it is to start the fluorescent. “Placing your hand on the tube or stroking it creates a very effective ground plane.” Magicians have been lighting “naked” fluorescent bulbs for quite a long time by serving as the ground plane.
But most of us aren’t magicians, and most of us use fluorescent lamps inside of metal fixtures. Why do the lamps usually light with a flick of the switch at some times and then other times require a little massage? J. Robert Moody, of General Electric’s Lighting Information Center, was kind enough to supply an answer that doesn’t require a physics degree to understand.
Under normal conditions, fluorescent lamps should light without difficulty, with the electric current flowing inside the fluorescent tube. But if the lamp has a combination of a light coating of dust and a small amount of moisture from the air, the coating will allow “some of the electric current to flow on the outside of the tube, and the current on the outside of the bulb will prevent the lamp from lighting. Under this condition, stroking the tube will interrupt the flow of current on the outside of the tube and cause the light to come on.”
Submitted by Harold J. Ballatin of Palos Verdes, California
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