A water lily is a floating aquatic plant with large, fragrant, white or pink flowers and flat, round, floating leaves. The leaves have long stems and are bright green above and reddish or purplish underneath. The underside of the leaf contains air spaces; the air that traps beneath the leaf makes it float on water. The leaves’ strong stems help them grow and stay upright in the water—which allows the leaves to absorb sunlight and stay alive.
Nobody who has died has been able to come back to tell us about it, so it is impossible to know whether dying hurts. But people who have had “near-death” experiences— those whose hearts have stopped, for instance, but were later restarted— have only good things to report. Most tell of a peaceful sensation of floating above their bodies. A number also describe traveling through a tunnel toward a beautiful light or having loving meetings with friends and relatives who have died before them.
Scientists know that when a person is in a state of very low oxygen—often a condition that precedes death—he or she experiences feelings of euphoria, or great happiness. So as far as we know, the act of dying is not painful at all. Many sick people welcome death. The same wonders of medicine that have allowed people to reach old age have also enabled them to live through long, and sometimes painful, illnesses. Often, death is seen as a welcome end to pain, both for the ill person and for the family and friends who have watched their loved one suffer. People with strong religious faith, too, may fear death less because they believe they will journey to a better place.
Early in human history, people used anything that they could find to keep their teeth clean. Usually a thin, sharp object, like a stick, was used to pick out food left between teeth. Chewing on the end of certain sticks would fray the wood, making a kind of brush, which could then be rubbed across the teeth. (Even today, members of primitive tribes chew sticks to keep their teeth clean. The constant chewing produces more saliva than usual, which helps wash food away.) Later, people found that if they rubbed abrasive elements, like salt or chalk, across their teeth, they could get rid of grime. They also used water and pieces of rough cloth to clean their teeth. Toothpicks made of all kinds of materials also became popular. Rich people had jeweled toothpicks made of gold and silver. Toothbrushes for the wealthy, with fancy handles and hog bristles, came into use in the eighteenth century.
Only much later, when cheaper, woodenhandled toothbrushes were made, and the importance of good dental hygiene became known, did most people start to regularly use them.
A charley horse a muscle cramp, or sudden, uncontrolled contraction of a muscle. This type of pain is generally felt in the legs, sometimes after heavy exercise, and usually lasts just a few minutes.
The expression probably came from the word “charley,” which is used to describe a horse that is lame.
Located in Arizona and stretching to Colorado, the Grand Canyon is 18 miles (29 kilometers) wide, 227 miles (365 kilometers) long, and 6,000 feet (1,828 meters) deep in its deepest section. It takes about two days by foot or mule to travel from the top to the bottom.
Although it is not the biggest canyon in the world—Barranca de Cabre in northern Mexico and Hell’s Canyon in Idaho are deeper—it is known for its amazing landscape. The canyon’s walls are made up of rocks, cliffs, hills, and valleys formed millions of years ago, and it is home to hundreds of species of mammals, reptiles, and birds. Although people lived in the canyon some 4,000 years ago, today it is a national park and national landmark.
The word computer first appeared in the seventeenth century as the job title of a person who did calculations as an occupation.
Although slide rules were sometimes called computers, it wasn’t until the 1940s, with the development of massive electronic data machines, that the human occupation of computing became obsolete. These mechanical devices became known as computers.
Almost everything we do is governed by some set of rules. There are rules for games, for sports, and for adults in the workplace. There are also rules imposed by morality (or ethics) that play an important role in telling us what we should and should not do. However, some rules—those made by the state or the courts—are called “laws.”
Laws are designed to control or alter our behavior, and to help make society a more ordered place. If people were allowed to choose at random what to do and how to behave, our country would be dangerous and chaotic. Laws that govern business affairs help businesses to operate properly, and laws against criminal behavior help to protect personal property and human life.
There are three general forms of government, based upon who rules: (1) those governments in which the authority is placed in one single person, (2) those dominated by several people, and (3) those controlled by many. In some nations, governing is done by a single individual, such as a king, queen, or dictator. This form of government is known as an autocracy. An autocratic government is called an oligarchy if a small group, such as landowners, military officers, or wealthy merchants, make up the government. If the country’s people make up the government and contribute to its decision-making process, that nation’s government is known as a democracy. There are also several ways in which governments do their governing. Limited governments, such as the United States and most countries in Western Europe, are known as constitutional governments, since these governments are limited as to What they are permitted to control. In other words, they have limited power, and this limited power is enforced by a separation of powers.
Most of these nations have constitutions that define the scope of governmental power. In contrast to a constitutional government, a government is called authoritarian when it has no formal limits; the government is limited by other political and social institutions in the land—such as churches, labor unions, and political parties. While these governments are sometimes responsive to these sources of limitation, there is no formal obligation for the government to represent its citizens. Examples of recent authoritarian governments include Spain from 1936 to 1975 under General Francisco Franco. Totalitarian governments attempt to control every area of political, economic, and social life and are usually associated with dictators who seek to end other social institutions that might challenge the government’s complete, or total, power. Some examples of totalitarian governments include Nazi Germany from 1933 to 1945 under dictator Adolf Hitler, the Soviet Union from 1928 to 1953 under dictator Joseph Stalin, and Cuba from 1959 to 2008 under Fidel Castro.
A rainbow is an arc that shows all the colors, with their different wavelengths, that make up visible light. Seven colors make up a rainbow, and they always appear in the same order: red, with the longest wavelength, is on the top, followed by orange, yellow, green, blue, indigo (a deep reddish-blue that is often difficult to see), and violet, which has the shortest wavelength. A good way to remember the order of those colors is by taking the first letter of each to spell “ROYGBIV,” pronounced “roy-jee-biv.” A rainbow occurs when sunlight passes through water droplets and is refracted or bent by their rounded shape into separate wavelengths.
Rainbows can sometimes be spotted in the spray of lawn sprinklers, in the mist of waterfalls, and—most spectacularly—in the sky during a rain shower when the Sun is still shining. A rainbow appears in the part of the sky opposite the Sun. Because the Sun must also be low in the sky, near the horizon, late afternoon is the best time to look for a rainbow if the day has been sunny with a few short rain showers or thunderstorms.
One reason is that the metric system is based on the number 10. The metric system emerged in the late eighteenth century out of a need to bring standardization to measurement. But 10 was important before the metric system. For example, Nichomachus of Gerasa, a second-century mathematician from Judea, considered 10 a perfect number, the figure of divinity present in creation with humankind’s fingers and toes. Pythagoreans believed 10 to be “the first-born of the numbers, the mother of them all, the one that never wavers and gives the key to all things.”
And shepherds of West Africa counted sheep in their flocks by colored shells based on 10, and 10 had evolved as a “base” of most numbering schemes. Some historians believe the reason 10 developed as a base number had more to do with ease: 10 is easily counted on figures and the rules of addition, subtraction, multiplication, and division for the number 10 are easily memorized.