Though most bees fill their days visiting flowers and collecting pollen, some bees take advantage of the hard work of others. These thieving bees sneak into the nest of an unsuspecting "normal" bee (known as the host), lay an egg near the pollen mass being gathered by the host bee for her own offspring, and then sneak back out. When the egg of the thief hatches, it kills the host's offspring and then eats the pollen meant for its victim. Sometimes called brood parasites, these bees are also referred to as cuckoo bees, because they are similar to cuckoo birds, which lay an egg in the nest of another bird and leave it for that bird to raise. They are more technically called cleptoparasites. Clepto means "thief" in Greek, and the term cleptoparasite refers specifically to an organism that lives off another by stealing its food. In this case the cleptoparasite feeds on the host' hard-earned pollen stores.

Humans usually experience sound as the result of vibrations in air or water. Although sound that humans can sense is usually carried through these media, vibrations can also travel through soil, including rocks. Thus, sound can travel through a variety of substances with different densities, and the physical characteristics of the medium through which the sound travels have a major influence on how the sound can be used. For instance, it requires more energy to make water vibrate than to vibrate air, and it requires a great deal of energy to make soil vibrate. Thus, the use of vibrations in communication depends on the ability of the sender to make a substance vibrate. Because of this, large animals such as elephants are more likely than small animals to use vibrations in the soil for communication. In addition, the speed at which sound travels depends on the density of the medium which it is traveling through.

The repairman is called in when the smooth operation of our world has been disrupted, and at such moments our dependence on things normally taken for granted (for example, a toilet that flushes) is brought to vivid awareness. For this very reason, the repairman's presence may make the narcissist uncomfortable. The problem isn't so much that he is dirty or the job is messy. Rather, he seems to pose a challenge to our self-understanding that is somehow fundamental. We're not as free and independent as we thought. Street-level work that disrupts the infrastructure (the sewer system below or the electrical grid above) brings our shared dependence into view. People may inhabit very different worlds even in the same city, according to their wealth or poverty. Yet we all live in the same physical reality, ultimately, and owe a common debt to the world.

Adolescence is a stage of development in which teens have superb cognitive abilities and high rates of learning and memory because they are still riding on the heightened synaptic plasticity of childhood. These abilities give them a distinct advantage over adults, but because they are so primed to learn, they are also extremely vulnerable to learning the wrong things. How does this happen? It is all because the brain wants rewards and anything that is learned, good or bad, that stimulates the production of dopamine is interpreted by the brain as a reward. This means a little bit of stimulation to a teenage brain whose synapses are firing all over the place leads to wanting more stimulation that can, in certain situations, result in a kind of overlearning. The more commonly known name for this overlearning is addiction.

Businesses of design and entertainment are essentially competing with one another to predict the consumer's taste―but also have some ability to influence it through clever marketing plans. In fashion, there is something of a cottage industry to predict which colors will be popular in the next season. This must be done a year or so in advance because of the planning time required to turn around a clothing line. If a group of influential designers decide that brown will be the hot color next year and start manufacturing lots of brown clothes, and they get models to wear brown, and stores begin to display lots of brown in their windows, the public may well begin to comply with the trend. But they're responding more to the marketing of brown than expressing some deep underlying preference for it. The designer may look like a savant for having "anticipated" the popular color, but if he had picked white or lavender instead, the same process might have unfolded.

An independent artist is probably the one who lives closest to an unbounded creative situation. Many artists have considerable freedom from external requirements about what to do, how to do it, when to do it, and why. At the same time, however, we know that artists usually limit themselves quite forcefully by choice of material and form of expression. To make the choice to express a feeling by carving a specific form from a rock, without the use of high technology or colors, restricts the artist significantly. Such choices are not made to limit creativity, but rather to cultivate it. When everything is possible, creativity has no tension. Creativity is strange in that it finds its way in any kind of situation, no matter how restricted, just as the same amount of water flows faster and stronger through a narrow strait than across the open sea.

Evolution works to maximize the number of descendants that an animal leaves behind. Where the risk of death from fishing increases as an animal grows, evolution favors those that grow slowly, mature younger and smaller, and reproduce earlier. This is exactly what we now see in the wild. Cod in Canada's Gulf of St. Lawrence begin to reproduce at around four today; forty years ago they had to wait until six or seven to reach maturity. Sole in the North Sea mature at half the body weight they did in 1950. Surely these adaptations are good news for species hard-pressed by excessive fishing? Not exactly. Young fish produce many fewer eggs than large-bodied animals, and many industrial fisheries are now so intensive that few animals survive more than a couple of years beyond the age of maturity. Together this means there are fewer eggs and larvae to secure future generations. In some cases the amount of young produced today is a hundred or even a thousand times less than in the past, putting the survival of species, and the fisheries dependent on them, at grave risk.

Driving is, for most of us, what psychologists call an overlearned activity. It is something we are so well practiced at that we are able to do it without much conscious thought. That makes our life easier, and it is how we become good at things. Think of an expert tennis player. A serve is a complex maneuver with many different components, but the better we become at it, the less we think of each individual step. One of the interesting things about learning and attention is that once something becomes automated, it gets executed in a rapid string of events. If you try to pay attention, you screw it up. This is why the best hitters in baseball do not necessarily make the best hitting coaches.

The difference between learning by instruction and learning by discovery is primarily a difference in the materials on which the learner works. When he is being instructed―discovering with the help of a teacher―the learner acts on something communicated to him. He performs operations on discourse, written or oral. He learns by acts of reading or listening. Note here the close relation between reading and listening. If we ignore the minor differences between these two ways of receiving communication, we can say that reading and listening are the same art―the art of being taught. When, however, the learner proceeds without the help of any sort of teacher, the operations of learning are performed on nature or the world rather than on discourse. The rules of such learning constitute the art of unaided discovery. If we use the word "reading" loosely, we can say that discovery is the art of reading nature or the world, as instruction is the art of reading books or, to include listening, of learning from discourse.

In the past few years, many new devices have been developed to assist people with sight problems. A laser cane, for example, helps blind people walking around. It sends out three beams of light. If the beams hit something, the cane makes sounds. The sounds warn a walker if something is in the way at head, waist, or foot level. One company has also invented traffic lights that make a difference sound when each color light is illuminated. Another company has created talking street signs that tell what street a walker is approaching. More complex machines have been created to help people read. One machine magnifies type to many times its printed size to make it easy for people with poor sight to read.

Grammar is the branch of linguistics which deals with the form and structure of words, and their interrelation in sentences. While many people, influenced by writing, tend to think of words as the basic units of grammatical structure, linguists recognize a smaller unit, the morpheme. The word cats, for instance, consists of two elements, or morphemes: cat, the meaning of which can be roughly characterized as "feline animal," and -s, as "more than one." Antimicrobial, meaning "capable of destroying microorganisms," can be divided into the morphemes anti-(against), micorbe(microorganism), and -ial, a suffix that makes the word an adjective. The study of these smallest grammatical units and the ways in which they combine into words, is called morphology.

Some people insist that children's baseball leagues should use baseballs that are softer than those used by adults and professional leagues. Yet both kinds of balls have their risks. The balls can cause a sudden stopping of the heart when they hit a child in the chest. That might seem hard to believe, but research has shown that a softer ball can also cause the heart to stop. Furthermore, in some circumstances, the softer ball triggers this rare but dangerous response even more than a harder ball does. In addition, a softer ball poses the same risk for eye injury. A softer ball may prevent a serious head injury, but a fast-moving ball of any type is likely to damage the eye socket, seriously hurting the eye.

This is a true story about two ships. One of the ships really existed and the other was created by a fiction writer. The first passenger ship was called the Titanic. It set out on its first trip from a starting point in Southampton, England, in April, 1912. Its destination was New York. One night, the ship hit an iceberg and began to sink. The ship did not have sufficient lifeboats for all passengers, and therefore many people died. The second passenger ship, the Titan, was described in a book by Morgan Robertson. It was almost the same size as the Titanic. The Titan submerged on an April night after it hit an iceberg, and many people died because there were not enough lifeboats. You might think Robertson had copied the true story of the Titanic in his fiction book, but he had not. Robertson wrote his novel in 1898. That was 14 years before the Titanic set out on its voyage.

Although the first thing that comes to mind when we hear the word ballet is a graceful ballerina gliding across the stage, the ballet is not just dancing. The final production is a combination of four arts: dancing, music, drama and painting. It is also a combination of the efforts of many people. The ballerina and her partner dance the main roles. It may be hard to realize that behind their seemingly effortless movements are long years of practice. Some of the people who create a ballet never appear on stage. They are responsible for the music to which the dancers move, the theme of the ballet's story, the sets, and the costumes. It is the fusion of these many talents that creates the one, overall effect that is a ballet.

Most nutritional science involves studying one nutrient at a time. The problem with nutrient-by-nutrition science is that is takes the nutrient out of the context of the food. This nutrient bias is built into the way science is done. Scientists study variables they can isolate; if they can't isolate a variable, they won't be able to tell whether its presence or absence is meaningful. Yet even the simplest food is a hopelessly complicated thing to analyze, a virtual wilderness of chemical compounds, many of which exist in intricate and dynamic relation to one another. So if you're a nutrition scientist, you do the only thing you can do, given the tools at your disposal: Break the thing down into its component parts and study those one by one, even if that means ignoring subtle interactions and contexts and the fact that the whole may well be more than, or maybe just different from, the sum of its parts.

"Cloud seeding" is a process used by several western state governments and private businesses, such as ski resorts, to increase the amount of rainfall or snow over a certain area. First, meteorologists use radar, satellites, and weather stations to track storm fronts. Then they measure a storm's clouds for temperature, wind, and composition. When the meteorologists determine that conditions are right, pilots are sent to "seed" the clouds with dry ice(frozen carbon dioxide). An aircraft files above the clouds, and dry ice pellets are dropped directly into them. Almost immediately, the dry ice begins attracting the clouds' moisture, which freezes to the dry ice's crystalline structure. Finally, precipitation drops from the clouds to the earth in the form of rain or snow.