Karen Hill

What the United States Census Bureau calls the geographic center of area is the point on which the surface of a geographical entity would balance if the surface were a plane of uniform weight per unit of area. For the United States, that point has been in Butte County, South Dakota, on the state’s western … Read more

The current plans involve bringing along a rocket that could be launched from Mars into a low orbit, where it would meet another craft that would return to Earth. The vehicle that returns to Earth would carry some kind of Earth-entry vehicle, like a capsule or shuttle plane. To make the return cheaper by bringing … Read more

Yes, a gun fired in space or on a space station or rocket ship should work as well as it would on Earth or possibly even better. The laws of physics still apply in space. The path of the bullet should be fairly straight, as gravity is greatly reduced, though not entirely absent. There may … Read more

There is growing evidence that exercise can help astronauts recover from muscle and bone losses and limit such losses. In the near absence of gravity, bone mass decreases in the load-bearing regions of the skeleton, and muscles shrink when not used. But Michael Foale, who was on the Russian space station Mir for four and … Read more

It has largely to do with the fidelity of the microphones, not the quality of space-to-ground communications systems. The astronauts wear wireless mikes that are as light and unobtrusive as NASA can make them. An FM signal goes from the astronaut to a communications device, then is radioed through a satellite system to the ground. … Read more

Shortly after the shuttle clears the launching tower, the software of its automated guidance, navigation, and control system initiates a roll command to line it up on the desired course and heading. The roll program tells the engine nozzles how much to gimbal, or swivel, to aim the shuttle properly. It goes straight up for … Read more

Parents have supposedly explained human reproduction to children in terms of the birds and the bees. If birds were really used to make this explanation, it would be widely believed that fertilization occurs after the briefest period of proximity of the waste elimination organs. Most birds do not have external sex organs. The transfer of … Read more

Smaller eagles have occasionally been “domesticated” by falconers and were traditionally reserved for the hunting pleasure of medieval kings. The American bald eagle, which has a wingspan of up to 7 feet and would therefore require a very large falconer, has been reliably reported to have lived for 30 years and 5 months in captivity … Read more

The assumption that a bird’s tail functions only as a horizontal surface is erroneous. A bird also can twist its tail from left to right and downward, so it acts almost as a braking system that allows it to bank into turns. Some birds are better at this than others. Some hawks in the group … Read more

The pinkness of flamingos is determined by food, but not by pink shellfish. The factors in the flamingo diet that ensure pinkness are carotenoid pigments, which are found in plankton, diatoms, and blue-green algae that the birds strain out of the muck in which they feed. The birds process yellow carotene into a red compound, … Read more

The winner, wings down, is the peregrine falcon, Falco peregrinus, which may also be the fastest animal of any kind on earth. Estimates of its top speed when diving start around 200 miles per hour, and some authorities put it considerably higher, perhaps 275 m.p.h. Its top horizontal speed is 60 m.p.h. or more. The … Read more

Short of exterminating all the crows in town, there is not much chance of getting rid of them. Driving out one family simply opens a place for another young male to move in. One possible way is to make things less attractive, but what attracts crows is the same thing that makes gardens attractive to … Read more

Like mammals, birds take in air and extract oxygen from it to supply body tissues, while fish respiration depends on getting the oxygen dissolved in water through organs called gills. But bird respiration is significantly different from that of mammals. In the very efficient avian system, the lungs are small, taking up just 2 percent … Read more

Yes, and though it is highly variable from species to species, research is leading to a higher estimation of birds’ smelling abilities. Sensitivity to odors varies among orders of birds with the size of the olfactory bulb in the brain relative to that of the cerebrum. The bulb tends to be small, but it is … Read more

Probably, based on structural features and fossil evidence, though some scientists studying DNA evidence suspect otherwise. There are studies, primarily of mitochondrial genes, suggesting that guinea pigs might not be rodents, but might belong to their own separate order. (Mitochondrial DNA is carried by the structures in cells that act as cellular power plants. It … Read more

There is no special equipment, just a highly developed ability to imitate. The ability to imitate a species’ own song is present in all songbirds. Some birds, like woodpeckers or chickens, do not actually learn songs. But of the birds that do, some learn a little and some learn a lot. Among the star imitators … Read more

Yes, in some cases. Kidney transplants were pioneered by the School of Veterinary Medicine at the University of California at Davis and are now performed at some other veterinary colleges around the country. They can cost $3,000 or more. There are no other transplant programs for dogs or cats, though there was initial research on … Read more

Brain size is not generally seen as a reflection of intelligence in dogs or in other species. That is evident if you compare other species with different brain sizes — for example, elephants and people: People are far more intelligent despite the huge disparity in physical size. Intelligence has more to do with the development … Read more

“Sense” in its physical meaning is the key word. Many case reports cite instances of animals’ behaving in strange ways before natural phenomena, but there is little scientific data. Domestic animals, dogs and cats in particular, have hearing and other sensory capacities that are greater than those of people. Their hearing is more sensitive and … Read more

There are two approaches. One is avoiding the buildup of the charge; the other is discharging it so you cannot shock the cat or yourself. The cat also builds up a charge, but because of its smaller size, most of the flow is from you to the cat. In friction between any two materials with … Read more

Whiskers give cats important sensory information and also have a role in communication between cats. They are far more important to a cat than a dog’s whiskers are to a dog, and they should never be trimmed, as they tell a cat whether it can squeeze through a narrow passage, for example. Technically called vibrissae, … Read more

Yes, allergies are common in cats and dogs. They arise by similar mechanisms and can cause similar symptoms, though skin eruptions are more common in cats and dogs than sneezing or digestive distress. Treatments may be similar, too. In an allergy, the animal’s immune system is hypersensitive to some substances it encounters, called allergens. For … Read more

It is probably more evolutionary than it is anything physiological, and is possibly related to hunting techniques. It is not usually seen in farm cats, who have to work for a living. Their predatory behavior involves sitting beside a mouse hole for hours, then pouncing. Instead, the mad dash is often seen among well-fed, secure, … Read more

One recent estimate is 10 million to 13 million living species. A 1988 study said only about 1.5 million species then had scientific names, though far more certainly exist. The study pointed out that “total” figures are not actual counts, but theoretical reckonings based on things like the number of species that make up typical … Read more

Although it can be difficult to know with certainty, there are clues in the shape and size of bony landmarks on the skull. You usually can’t sex other bones reliably, except for the pelvis. With the skull, what scientists look for is the difference between what is called robust morphology, meaning typically heavier, larger shapes … Read more

They are cousins but belong to different families. All are members of the cetacean order, which includes whales, and all belong to the suborder odontoceti, literally meaning toothed whales. The thirty-two species of seagoing dolphins (members of the family Delphinadae) are perhaps most easily distinguished from the six species of porpoises (members of the family … Read more

In some whale species, a third whale may have a role in courtship, but it is now thought to involve competition, not assistance. The California gray whale, Eichrichtius robtistus, has many more males than females. During courting, two males will often follow one female, and the trio will stay together right up to the moment … Read more

Yes, some fish are simultaneously hermaphroditic, possessing the reproductive equipment of both sexes at one time; a few can fertilize their own eggs. In some species, called sequential hermaphrodites, an individual can change from male to female, from female to male, or back and forth. Some fish species are entirely female and reproduce by cloning … Read more

The several species of oceanic flying fish seem to take flight either when they are alarmed or when they are attracted by a light shining in the night. Most flying fishes belong to the family Exocoetidae and live in the surface waters of all tropical oceans. They are able to leap out of the water … Read more

There is no special name for the sticky substance, but scientists do know it is secreted by mucous glands at the moment the frog’s tongue hits the prey. Otherwise it would stick the frog’s mouth together. The tongue of a frog, which is hinged at the front of the mouth, not the back, can be … Read more

There are two groups of lizards commonly called chameleons, and they change colors in different ways. True chameleons belong to an Old World family called Chamaeleontidae, with two genuses and about eight-five species. They have a variety of colorations, which they can change, to a greater or lesser extent, by concentrating or spreading out the … Read more

Rattlesnakes are good swimmers, though they are not in a class with species that spend all or most of their lives in water or even with the familiar garter snake. From anecdotal accounts, we know that rattlesnakes will swim readily enough when their travels in search of food, mates, or refuge require them to cross … Read more

The turtle lives ‘twixt plated decks Which practically conceal its sex. I think it clever of the turtle In such a fix to be do fertile. The poet Ogden Nash was right about the turtle’s external ambiguity and fertility. Turtles are not only enthusiastic breeders, they also have external sexual characteristics that often make it … Read more

Most snakes have specialized body structures that let them swallow things that are larger than their heads or necks. First, a snake’s skin is very elastic. Even more important is the fact that the snake’s jaws are made up of four elements, not two, and they are only loosely attached with ligaments that can stretch … Read more

As you suspect, the chirping noise a chipmunk makes probably has less to do with foraging, as the familiar fat-cheeked eastern chipmunk (Tamias stratus) can easily collect and store a life-time supply of food in a single season, than with protecting territory and warning off interlopers. Chipmunks have a variety of vocal sounds, not all … Read more

The subject is a confusing one because of the rather inexact use of terms in most post-Roman cultures. Especially large or poisonous snakes are commonly called serpents, and biblical tradition calls the shape Satan assumed to tempt Eve a serpent. But technically speaking, all snakes can be called serpents, from the Latin derpere, meaning to … Read more

Beavers make their complex domestic arrangements to improve security from predators and to move and store a reliable food supply. Dam building is only one of their construction activities, along with canal building and lodge building. The dammed-up ponds make an important contribution to the beavers’ well-being by creating storage at the right depth to … Read more

They are very closely related, so closely that they are now usually considered different races of the same species, Rangifer tarandus. Even the somewhat smaller domesticated reindeer are part of the same group. Caribou coloration varies widely, from nearly black to brown to gray to almost white, and some populations migrate hundreds of miles, with … Read more

Horses can doze standing up and spend more time upright than other animals, but get their deepest rest, the so-called REM sleep, only when lying down. In total relaxation, which rapid eye movement or dream sleep involves, the system of tendons and ligaments that keeps horses’ legs extended does not work. If a horse goes … Read more

Bears do hibernate, though not as deeply as some other hibernating animals. Deep hibernators spend most of the winter with drastically lowered body temperatures. Bears lower their body temperatures only slightly and continue to burn about 4,000 calories a day, resulting in a Zen-like state of watchful rest. They can quickly rouse themselves in response … Read more

The polar bear can breed with the brown bear, and the offspring would probably be fertile. But it would never happen in the wild. The ranges of polar and brown bears do not overlap, and even if two met, they would see each other as competitors, not mates. Such interbreeding has occurred in captivity, but … Read more

Pound for pound, a 40-pound wolverine, formally Gulo gulo, is simply stronger than many of its adversaries and is capable of killing animals much larger than itself. Wolves are probably aware of this. For example, a wolverine’s jaws are so strong that it can completely crush a frozen caribou’s large bones, part of its adaptation … Read more

All animals need various nutrients—things like amino acids and vitamins — to build and maintain their cells and to provide energy for bodily processes. Carnivorous animals get many of these nutrients ready-made from the other animals they eat. Vegetarian animals get the nutrients not just by chemically changing plant material through enzymatic processes but also … Read more

Dust mites are often referred to as tiny insects, but they are not. Instead, they are arachnids, part of the large group of eight-legged creatures that includes spiders and ticks. Several species of dust mite belong to the genus Dermatophagoides, a name that describes in Latin their way of life: They live mostly by devouring … Read more

It is partly a matter of appearances, with zoo animals less active at peak visiting hours, and partly a matter of normal rhythms of carnivore life. Lions in the wild are normally inactive for twenty to twenty-two hours a day because they need to conserve their energy for hunting, never being quite sure where their … Read more

It is hard to be sure, but depending on when the flies show up, you can make an educated guess. Flies have a particular amount of time to spend as egg, larva, and pupa before they climb out of the pupa. In the common fruit fly, this takes about eight to perhaps ten or twelve … Read more

In some species of cricket, the number of chirps per minute used by the male to attract females rises and falls along with the outside temperature, and can in fact be used as a rough thermometer. Since insects are small (with a high surface-to-volume ratio) and cold-blooded, with relatively slow metabolisms unless they are exerting … Read more

With some exceptions, spiders in temperate regions have one-year life spans, with the females outliving the males by weeks or months. Perhaps the most interesting exceptions belong to the family Lycosidae, or wolf spiders. Some members of this family live in elaborate silk-lined underground burrows. The females protect their eggs in sacs that they carry … Read more

Unfortunately, no. There are many species of mosquitoes, perhaps 3,000 worldwide and 150 in the United States. The females, which seek a blood meal to produce eggs, have many different kinds of feeding habits. While many of the mosquitoes that carry disease are most active at dawn and dusk, even they may be roused to … Read more

Scorpion experts have found that scorpion species with smaller and more slender claws typically have more toxic venom. But just as with bee stings, any scorpion’s sting can be fatal to a person who is severely allergic to it. Toxicity of the venom also varies by species and prey. A species’ particular cocktail may contain … Read more

How high an insect can fly depends on air temperature. Generally speaking, most insects can fly as long as they stay in air above 50 degrees Fahrenheit. If the air temperature at ground level is 90 degrees, the 50-degree border is around 6,000 feet; if ground temperatures are in the 70s, the ceiling is around … Read more

You may have observed female dragonflies depositing their fertilized eggs into the water, where they will hatch into larvae. The eggs are sometimes inserted into underwater plant stems and sometimes smeared onto the surface of the water. More than three hundred eggs may be laid at one time. Sometimes several hundred females lay their eggs … Read more

That is the right time of year for the eastern monarchs’ migration, and they do congregate in Cape May, New Jersey, by the thousands. The monarchs seen in and around New York City are flying through on the way to their wintering sites in the mountains of central Mexico. The butterflies seek out microclimates congenial … Read more

The energy is gathered from nectar, and the butterflies that make the trip, those born in the early fall, are able to convert nectar into fat. Those born in September know to fill up on nectar. Their abdomens get really large. Unlike the other generations, these monarchs have a little area of fatty tissue where … Read more

While they do not exactly scream, some caterpillars have noise-making organs, and the sound they produce is used to call in troops of ants to protect them from predatory wasps. The noise has an average frequency of 1,877 hertz, which would be audible to human ears if it were not so very faint. Some noisy … Read more

If there was any foreleg contact or waving about of antennae by the ants, some communication may have been involved. But the wide range of communication methods among ants is weighted heavily toward chemical signals, and visual signals have not been solidly documented. Ant communication, which has been extensively but not exhaustively studied, includes tappings, … Read more

Several ant species “herd” the small pear-shaped insects called aphids and “milk” them for a sweet fluid that they excrete after feeding on sap from roots or leaves. They are sometimes called dairying ants. Ants that “milk” root-eating aphids often dig them chambers to serve as “barns.” The ants protect their aphids, carry them from … Read more

Brain wrinkles seem to have more to do with what makes humans smarter than lower animals than with what might have made Einstein smarter than you. In normal human brains, large grooves called fissures, small ones called sulci, and outward folds called gyri follow a standard plan from person to person. Lower animals have smoother … Read more

The stomach is not essential for human survival. Many people have survived and adjusted to total or partial surgical removal of the stomach because of diseases like stomach cancer. The stomach is essentially a reservoir that allows people to eat the quantity of food they want, emulsify it, and pass it gradually into the small … Read more

Like other important organs, teeth have nerves for sensation and protection. The diseased “nerve” removed in a root canal procedure is the common term for the combination of nerves and blood vessels that form pulp, the soft interior of the tooth. There is also a bundle of nerve fibers in the ligament that attaches the … Read more

If the lump is stress related and does not involve serious difficulty in swallowing, it is probably just an exaggerated awareness of the epiglottis or spasms of muscles surrounding the throat. After ruling out physical ailments that can cause the feeling of a lump in the throat, like throat cancer or esophageal reflux, in which … Read more

Yes, eventually, but it is not a simple matter of sleeping longer on a weekend after being denied adequate sleep for some days. In extreme cases, experts say, you may need six weeks of adequate sleep to repay a long term sleep deficit. Several studies have found that the amount of recovery sleep required to … Read more

The small piece of soft tissue dangling over the tongue is the uvula. It is variously described as U-shaped or tear-shaped, or classically speaking, grape-shaped; its name comes from the Latin word for grape. While some anatomy experts think it is only a vestigial organ, not all would agree with your teacher that it has … Read more

Many of the explanations offered for the sharp pain runners feel during hard breathing, usually on the right side, involve muscle stress or spasms in or near the diaphragm. Because the muscle stress is probably caused by a rhythmic, repetitive activity, the solution is to develop techniques to break up that stressful rhythm. Runners could … Read more

The brain can tell which tickling sensations are caused by one’s own actions and gives them low priority, so that it can be more receptive to sensations from outside sources that may be more urgent. One study suggests how brain areas may interact to do this. In the study, a magnetic resonance imaging device scanned … Read more

You are not alone, because about 30 percent of the population seems to have the same problem. The classic ice cream headache is a stabbing pain that usually peaks after thirty to sixty seconds, though it can last up to five minutes. A doctor who gets such headaches, Dr. Robert Smith, founder of the Cincinnati … Read more

Not according to experts. In fact, children can focus up close without eyestrain better than adults. That is because the lens, which changes its focus for nearby and faraway viewing, tends to lose some of its flexibility as people grow older. Usually, sitting very close to the television set is a habit that children grow … Read more

Ordinary hiccups, resulting from things like overeating and stress, are usually benign. But hiccups can indicate a serious problem, and a prolonged, uncontrollable bout may lead to debilitating consequences like fatigue, weight loss, depression, problems with heart rhythm, esophageal reflux, and possibly exhaustion and death in a weakened patient. In a famous case, Pope Pius … Read more

Nobody has specifically studied this aspect of sneezing, but there are logical reasons that would explain why people do not sneeze overnight. The reason people sneeze is that the inside of the nose swells up, much like blowing up a balloon. When a windblown particle of anything, an allergen or a particle of dust, hits … Read more

Rigor mortis is gradual, usually noticeable about three to four hours after death, and the timing varies with several factors, including the person’s activity just before death and the temperature of the body’s surroundings. How long it takes the muscle stiffness to subside also varies, with rigidity usually reaching a peak after twelve hours and … Read more

The eyes have a very efficient radiator as well as a surface deicing system, at least in theory. The eye has a system of blood vessels that provides a constant irrigation of warm blood through and around the eyeball to keep it warm. This makes freezing very unlikely. As for the surface of the eye, … Read more

Crime novels to the contrary, it is hard to dispatch someone with a needle unless you are expertly trying. It is standard practice to make sure air is cleared from a syringe before pushing the plunger, but the chances of death occurring because of the air a fine needle might carry in a normal injection … Read more

Organs may come from newborns on up, with no specific age limit. There was more of an age limit in the past, but now it is decided on a case-by-case basis. The oldest known donor of a liver was 92, in Canada, and there was one who was at least 85 in the United States. … Read more

A keloid is a scar that does not know when to stop forming, becoming large, shiny, smooth, and often pink and dome-shaped. It is not known why some people get overgrown scars after injuries, surgery, or acne, but keloids are more common among people of black and Asian descent, so a genetic factor is suspected. … Read more

Yes, but it is not a good idea except under very special circumstances, because too high a concentration of oxygen or oxygen at too high a pressure can be toxic. For example, when a diver gets too much oxygen at high pressure, oxygen toxicity can cause lung damage and even convulsions. However, pure oxygen in … Read more

A pinched, compressed, or entrapped nerve can be surrounded by swollen tissues or impinged upon by bony processes in many areas of the body. The cause can be injury, disease, or even pregnancy. The result is pain, numbness, tingling, and weakness in the part of the body to which the nerve normally carries impulses. One … Read more

The prevailing theory involves damage to the DNA of skin cells. It is the shorter UVB rays, which penetrate only the top layers of the skin, that are suspect, while the longer and more deeply penetrating UVA rays cause wrinkles and aging. In tissue cultures, UV damages the DNA of cells, but humans have an … Read more

There are treatments for vitiligo that are at least partly effective in many cases, but its cause is still under study. A prominent theory is that an autoimmune reaction is involved. The condition may also be associated with certain ailments, including thyroid disorders, and may flare up after injury, stress, or severe sunburn. Patches occur … Read more

Exposure to the sun’s ultraviolet radiation darkens granules of the pigment melanin in the surface layers of the skin. Part of the radiation also stimulates pigment-producing cells, called melanocytes, in deeper layers of the skin, causing a delayed-reaction tan, about three days after exposure. When the top layers of skin wear off, so does the … Read more

Skin changes that cause wrinkles do accompany aging, as the deeper layer of skin, the dermis, gets thinner. But it happens more quickly in sun-exposed areas and in people who smoke. The breakdown of two kinds of molecules, collagen and elastin, is at fault. Collagen type 1 is the molecule that makes up the bulk … Read more

The vermiform (Latin for worm-shaped) appendix, a dead-end branch of the intestines, plays at least a minimal role in the immune system and is also sometimes regarded as a potential spare part for replacing things like a diseased urinary bladder. Along with the adenoids, tonsils, and spleen, the appendix is classified as part of the … Read more

Such a condition is probably an inflammatory response to the irritation of having the eyes open and exposed to the drying air. The effect is common knowledge and a clear symptom of sleeplessness but has not been completely studied. Eye lubricants and tears dry in the air and may form scratchy particles. The skin around … Read more

Ear wax, known to scientists as cerumen (pronounced suh-ROO-mun), traps dust and dirt particles to keep them from going down the ear canal to the eardrum. Besides protecting against dirt and water and lubricating the canal, ear wax is slightly acidic, so some experts say it has mild antibacterial properties and helps fight the growth … Read more

If we leave aside the possible presence of diseases like arthritis or diabetes, several mechanical factors could make standing still more tiring than walking. First, the action of the muscles in walking keeps the circulation of both blood and lymph going, preventing the pooling of fluids in feet and ankles. For another thing, when a … Read more

Liver spots, also called age spots or lentigines, are the result of hyperpigmentation, or the buildup of excess pigment in patches of the skin. Liver spots have nothing to do with the liver and most often result from a lifetime of exposure to sunlight. Other possible causes include surgery, pregnancy, and some medications. Liver spots … Read more

Sensitivity to temperature is much more complicated than a simple gender split, physiologists say. The reaction depends on many factors, such as exercise, previous conditioning, diseases, and any other tinkering with the complex system of signals to and from the hypothalamus that sets the body’s temperature controls. Some doctors suspect psychological factors make a difference, … Read more

Medical literature contains few if any cases in which people have recovered after their inner, or core, temperatures dropped below 55 degrees Fahrenheit. Core body temperature is usually measured by elec, tronic sensors inserted into the digestive tract. It cannot be measured with an ordinary oral thermometer. Hypothermia is considered to exist whenever the core … Read more

What seems like frozen fingers is very subjective and could cover a wide range of temperatures. Having fingers that are icy cold is a real sensation and can be very distressing, but it is usually not reflective of something dangerous. What is more dangerous is where one finger is cold or has changed color, or … Read more

Artificial blood will not be available any time soon, and the need for donations will remain acute for the foreseeable future. Synthesizing blood is much more complex than synthesizing insulin. Blood includes many different kinds of cells, while insulin is a protein. There are ways to make hemoglobin, the protein in blood that carries oxygen, … Read more

The most basic classification of the hundreds of ways to type human blood, the ABO system, is important because incompatible types of blood react with each other to form sticky globs of red blood cells that can cause serious and sometimes fatal blockages. The classification was developed in 1901 by Karl Landsteiner, a Viennese-born pathologist … Read more