Camels are the only animals with humps. A camel’s hump is a giant mound of fat, Which can weigh as much as 80 pounds (35 kilograms). The hump allows a camel to survive up to two weeks without food. Because camels typically live in the deserts of Africa and the Middle East, where food can be scarce for long stretches, their hump is key to their survival. When camels are born their humps are empty pockets of flexible skin. As a camel grows and begins to form its fatty tissue reserves, the humps begin to fill out and take shape.
The humps also come in handy for humans who have domesticated the camel. For thousands of years, people have used these strong, resilient creatures for transportation and for hauling goods. The two-hump, or Bactrian, camel was domesticated sometime before 2500 B.C.E., probably in northern Iran, northeastern Afghan – istan, and northern Pakistan. The one-hump, or Dromedary, camel was domesticated sometime between 4000 and 2000 B.C.E. in Arabia.
There are many cities around the world that are “big,” meaning they have more than 10 million people living in them. Tokyo, Japan, ranks the largest, since it has 33.2 million people living in the city, according to 2005 estimates. The next biggest cities in order of size are São Paulo, Brazil (17.7 million), Seoul-Incheon, South Korea (17.5 million), Mexico City, Mexico (17.4 million), Osaka-Kobe-Kyoto, Japan (16.4 million), and New York City (about 8 million people).
Most of these cities are located in different places around the globe. In the United States, after New York, Los Angeles is the biggest city (with almost 4 million people), and then Chicago (with almost three million people). Populations of cities are constantly changing as people move in and out of them, according to the U.S. Census Bureau, a government organization that estimates how big or small cities are based on their populations, or the number of people living in them.
Human beings communicate through language, a complicated system of vocal symbols that our complex brains allow us to learn after we are born. But we also communicate through our bodies and senses. Our organ of touch is our skin, covering the outside of our bodies. (Nerve endings under the surface of skin give us our sense of touch.) Hugging and kissing are ways to share love and caring through touch. When you were born, well before you knew language and could understand caring words, you were learning about love through your sense of touch. As a newborn, when everything was frighteningly new, you immediately experienced the comfort of touch when you were held in your mother’s arms, feeling the warmth of her body and the beat of her heart, sensations familiar to you when you were inside her womb. You were held close when you first learned about food and about how good it felt to have milk in your empty stomach.
Your parents’ caring hands kept you clean and dressed in dry clothes when you could not yet do those things for yourself. So, from your earliest days, you learned that someone’s touch usually made you feel comfortable and safe. Loving and caring about special people in our lives is a feeling inside that is hard to describe in words. But hugs and kisses make it easy to show that love—and their message is clear. Giving hugs and kisses feels as good as getting them. (Because the lips have an extra supply of nerve endings, kissing is an especially intense way to touch.) The human need to share affection through touch is something we all experience throughout our lives.
The fastest growing hairs on the human body are men’s beard hairs. If the average male never trimmed his beard, it would grow to almost 30 feet (9 meters) long in his lifetime.
After a victory on a battlefield, the ancient Greeks would build a monument dedicated to a chosen god, which they called a “trophy.” These trophies were made of limbs stripped from the dead enemy soldiers and then hung on a tree or pillar, a ritual that is kept alive by modern “trophy hunters,” who celebrate their victory over an unarmed animal by hanging its head on the wall.
Be grateful for the Stanley Cup.
Dams, which are structures that hold back water, have been built since ancient times. They are usually made of earth, rock, brick, or concrete—or a combination of these things. They are constructed to control the flow of water in a river, and they are built for a number of reasons. One reason is to prevent flooding. Heavy rains in high country may cause water levels in a river to rise. As the river flows downhill, it may overflow its banks, flooding communities located downstream. A dam can prevent this by stopping or slowing rushing water, allowing it to be released at a controlled rate. Dams are also frequently used to store water for general use and farming. When a river’s flow is restricted by a dam, water often spreads out behind the dam to form a lake or reservoir in the river valley. That water can then be used as needed, preventing water shortages and crop damage during long periods of dry weather.
A great number of dams today are used to make electricity. Such hydroelectric dams are built very tall, to create a great difference in the height of the water level behind and in front of it. High water behind a dam passes through gates in the dam wall that allow it to fall to the river far below. As the water falls, it flows past huge blades called turbines; the turbines run generators that make electricity. One of the world’s largest and most productive hydroelectric dams is the Hoover Dam, located on the Colorado River between Nevada and Arizona. Built in the 1930s, it is 726 feet (221 meters) high and 1,244 feet (379 meters) long. Its reservoir (Lake Mead)—the world’s largest— supplies water to several states, allowing huge regions of naturally dry terrain in southern California, Arizona, and Mexico to flourish. Many modern dams are used for all three purposes: flood control, water storage, and hydroelectric power.
The story of Cinderella was passed along orally for centuries before it was written down by Charles Perrault in 1697. While doing so he mistook the word vair, meaning ermine, for the word verre, meaning glass.
By the time he realized his mistake, the story had become too popular to change, and so instead of an ermine slipper, Cinderella wore glass.
The Nobel Prize is the most famous international science award. Three science prizes, for chemistry, physics, and physiology or medicine, are awarded every year to people who have made significant contributions to these fields. The prize was created by the Swedish chemist and industrialist Alfred Nobel, who made a fortune from his invention of dynamite and left much of his money to fund the prize. Since 1901, the Nobel Prize has been honoring men and women from all parts of the world for their discoveries and inventions in these areas, as well as in the fields of literature and peace.
Some famous scientists and inventors who have been awarded the prize include Ivan Pavlov (in 1904), Albert Einstein (1921), and Linus Pauling (1954). Eleven women, from a total of 500 scientists, have been awarded a Nobel Prize in the sciences from 1901 to 2008. Among them, Marie Curie is the only person ever to have twice received a Nobel Prize in the sciences, each time in a different field of specialization: in Physics, in 1903, and in Chemistry, in 1911.
Governor William Penn established Pennsylvania’s first post office in 1683. Central postal organization came to the colonies after 1692, when Thomas Neale received a 21-year grant from the British Crown, whose settlements dominated the Atlantic seaboard, for a North American postal system. It wasn’t until 1774, however, that William Goddard, a newspaper publisher and former postmaster, set up the Constitutional Post for intercolonial mail service.
Colonies funded it by subscription, and net revenues were used to improve mail service rather than to pay back to the subscribers. By 1775, when the Continental Congress met in Philadelphia, Goddard’s post was flourishing, and thirty post offices operated between Williamsburg, Virginia, and Portsmouth, New Hampshire. The Constitutional Post provided security for colonial messages and created a communication line that played a vital role in bringing about American independence during the Revolutionary War.
Water is vital to the survival of everything on the planet and is limited in supply. Earth might seem like it has abundant water, but in fact only 1 percent is available for human use. While the population and the demand on freshwater resources are increasing (each person uses about 12,000 gallons of water every year), supply remains the same. Water is constantly being cleaned and recycled through Earth’s water cycle, yet we still need to conserve it because people use up Earth’s freshwater faster than it can naturally be replenished.
When you use water wisely, you help the environment. You save water for fish and animals, help preserve drinking water supplies, and ease the job of wastewater treatment plants—the less water you send down the drain, the less work these plants have to do to make water clean again. When you use water wisely, you also save the energy that your water supplier uses to treat and move water to you, and the energy your family uses to heat your water. Your family pays for the water you use, so if you use less water, you’ll have more money left to spend on other things.