When Do Fish Sleep? Part 11

Submitted by Dave Bohnhoff of Madison, Wisconsin.

Why Do We Dream More Profusely When We Nap than We Do Overnight?

According to the experts we consulted, we dream just as much at night as we do when we take a nap. However, we recall our afternoon-nap dreams much more easily than our dreams at night.

While we are dreaming, our long-term memory faculties are suppressed. During the night, our sleep is likely to go undisturbed. We tend to forget dreams we experience in the early stages of sleep. The sooner that we wake up after having our dreams, the more likely we are to remember them.

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.

Why Do Place Kickers and Field-Goal Kickers Get Yardage Credit from Where the Ball Is Kicked and Yet Punters Only Get Credit from the Line of Scrimmage?

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.

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.

How Does the Treasury Know When to Print New Bills or Mint New Coins? How Does it Calculate How Much Money Is Lost or Destroyed by the Public?

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 Was.h.i.+ngton, 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 s.h.i.+pping 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 const.i.tuent Federal Reserve Banks.

Submitted by Hugo Kahn of New York, New York.

What Is the Purpose of that Piece of Skin Hanging from the Back of Our Throat?

No, Ka.s.sie Schwan's ill.u.s.tration 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 pa.s.s 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.

Why Don't Birds Tip Over When They Sleep on a Telephone Wire?

A telephone wire, of course, is only a high-tech subst.i.tute 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 Mitch.e.l.l of Portland, Oregon.

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 ma.s.sage? 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.

Why Is There an Expiration Date on Sour Cream? What's the Matter, Is It Going to Get More Sour?

We've gotten this Imponderable quite often on radio interviews, usually from smug callers sure that expiration dates are a capitalist plot to force us to throw away barely used sour cream. But mark our words: if you think sour cream is tart when you open it, just leave it in the refrigerator too long and taste the difference. As the expiration date on sour cream becomes a dim memory, bacteria acts upon the sour cream, making it unbearably tart. Given enough time, mold will form on the sour cream, even if it is properly refrigerated.

Sour cream has about a month-long life in the refrigerator. Wait much longer and we'll bet that you won't want to test just how sour cream can get. If you think we're wrong, there's one way to find out for sure.

Go ahead and taste it. Make our day.

Who Translates the Mail When a Letter Is Sent to the United States from a Foreign Country that Uses a Different Alphabet?

If the United States Postal Service has problems sending a letter across town in a few days, we wondered how they contended with a letter sent to Nebraska from a remote village in Egypt. Does every post office hire a staff of linguists to pore over mail and route it in the right direction?

No, not every post office. But the USPS does employ linguists at their International Exchange Offices, located at the major ports (New York, San Francisco, Miami, and Boston) where foreign mail is received. All mail is separated and sorted at these border points and sent on its merry way.

We contacted some foreign consulates to find out how they solved the problem of indecipherable mail. A representative of the Greek consulate told Imponderables that if foreign mail is written in one of the international languages, multilingual personnel have no problem sorting it. If no postal worker can translate an address, the postal service will likely do what we did-call the emba.s.sy or consulate of the country of the sender and hope for the best.

Submitted by Charles F. Myers of Los Altos, California.

Why Do Roaches Always Die on Their Backs?

We couldn't believe that three readers actually had experienced the good fortune to see a dead roach and had torn themselves away from the subsequent celebration long enough to note the posture of the deceased insect. But we trudged on nevertheless, contacting entomologists who actually get paid to study stuff like this.

Professor Mary H. Ross, affiliated with Virginia Polytechnic Inst.i.tute and State University, told Imponderables that when a roach dies, its legs stiffen and the c.o.c.kroach falls on its side. Because most roaches have a flattened body form with narrow sides, the momentum of the fall rolls them onto their backs.

John J. Suarez, technical manager of the National Pest Control a.s.sociation, adds that small c.o.c.kroaches, such as the German and the brown-banded, are more likely to die on their backs. Larger c.o.c.kroaches with lower centers of gravity, such as the American and the Oriental, occasionally die face down.

Needless to say, we can't guarantee the position of dead roaches contained in traps. Maybe the lifeless occupants of Roach Motels lie perfectly p.r.o.ne. Unfortunately, there is only one way to find out and only entomologists have the stomach for it. Please don't try to verify this at home!

Submitted by Gloria Stiefel of Orange Park, Florida. Thanks also to Irma Keat of Somers, New York; and Gregg Hoover of Morgan Hill, California.

Why Does Warmth Alleviate Pain?

A caller on Tom Snyder's radio show posed this Imponderable. We had no idea of the answer, but it was surprising that so many physicians we spoke to didn't know the answer either.

We finally got the solution from Daniel N. Hooker, Ph.D., coordinator of Physical Therapy/Athletic Training at the University of North Carolina at Chapel Hill. His answer included plenty of expressions like "receptors," "external stimuli," and "pain sensors." So let's use an a.n.a.logy to simplify Hooker's explanation.