Unit 1- Alexander Graham Bell
Can you imagine living without a telephone or a cell phone? Until 1876, people didn’t have phones. Many scientists tried to invent the telephone, and Alexander Graham Bell finally succeeded in 1876. How did he first know that he made a successful telephone? One day, Bell spoke into one part of his machine, “Mr. Watson, come here. I want to see you.” Mr. Watson was his partner. He was in a different room of the same house. And Mr. Watson heard Bell’s voice out of the other part of the machine. It was the first telephone communication in history!
Unit 2- Comets
Do you know what a comet is? A comet is an object in the solar system. It travels around the sun like the planets. Then why don’t we call it a planet? Because comets are usually very small, and their orbits are not regular, they cannot be planets. Because their orbits are not regular, they sometimes crash into planets and disappear. So it is very hard to observe comets in the sky. However, there are some comets we can observe. For example, Halley’s Comet is very famous. Every 75 or 76 years, we can see it in the sky. So if you live very long, you can see Halley’s Comet more than once!
Unit 3- Penguins
Do you know where we can find penguins? Some penguins live near the South Pole. But others live in mild weather, too! And one kind of penguin lives in very hot areas. Penguins are found in many islands and continents in the southern parts of the Earth. For zoologists, it is a very important fact because it means that penguins could fly a long time ago. But now, penguins can’t fly, even though they are birds. But they can swim instead. Penguins are also good at walking. How fast can they walk? Penguins can walk faster than an average human!
Unit 4- Smog
What is smog? It is fog combined with dirt and dust in the air. Is it a natural event? No, it isn’t. In fact, smog is a type of air pollution. In big cities, smoke from automobiles and factories goes up into the sky and meets the moisture in the air. When the air cools down at dawn, a huge amount of the dirty moisture in the sky comes near the ground. And what happens? It forms smog! Smog is a huge problem for people in big cities. Smog causes many kinds of lung diseases and eye or nose problems.
Unit 5- Lenses
Do you wear glasses? How about contact lenses? Do you know what the similarities between glasses and contact lenses are? They help you see objects better. How can they do that? Glasses and contact lenses improve your eyesight, because both of them use some kind of lens. Generally, there are two kinds of lenses. One kind of lens makes you see things bigger. These kinds of lenses are used for magnifying glasses or glasses for old people. Another kind of lens makes you see things smaller. These are used for common glasses.
Unit 6- The Color Spectrum
Do you know what aspectrum is? It is a series of colored lights. How can we see a spectrum? Whenyou see sunlight through a prism, you may see a rainbow. This is the spectrumof light! Can you separate a color from one spectrum? No, it is impossible.People think there are only red, orange, yellow, green, blue, indigo, andviolet colors in a rainbow. Is it true? No, it isn’t. As a matter of fact,there are thousands of colors between each color. Therefore, a spectrum is aset of thousands of colors.
Unit 7- Nuclear Weapons
Do you know what the most dangerous weapon in the world is? Of course, every weapon is dangerous. But a nuclear weapon must be the most dangerous and powerful weapon. A nuclear weapon is a kind of bomb. It uses nuclear reactions to release energy. During World War II, American scientists developed a bomb using nuclear power. And the United States dropped nuclear bombs on two cities in Japan. What happened next? Over 120,000 people were killed! And these two cities were totally destroyed. Now everyone is afraid of nuclear weapons.
Unit 8- Geneticists
If your mum’s blood type is O, and your dad’s blood type is A, your blood type must be either A or O. How do we know this fact? Because some scientists studied human blood types, we know that one’s blood type is determined by the blood types of one’s parents. What do we call these scientists? Geneticists! Geneticists are the scientists that study genes and heredity. Geneticists usually study medicine, biology, chemistry, and so on. These days, some geneticists are working to make human clones! Do you think it is possible? They think it is!
Unit 9- Benjamin Franklin
Benjamin Franklin was an adventurous scientist. One stormy night, Benjamin and his son went outside and flew a kite to catch electricity. They attached a metal piece on the top of the kite and a metal key at the end of the string. After lightning struck the kite, Benjamin touched the key. It gave him a small electric shock! Fortunately he didn’t hurt himself, but it was a really dangerous experiment! Later, he invented a lightning rod. It is an iron stick on roofs of houses or buildings. It protects the houses and the buildings from lightning damage.
Unit 10- Shorelines
Is a shore different from a coast? Yes, it is! The word coast is used when land meets the ocean. The word shore is used when land meets a large body of water, like an ocean or lake. Therefore, a shore can be a coast because a coast is a kind of shore. The word shoreline describes the line where shore and land meet. How is a shoreline created? It is usually created by waves of water. Rocks and soil from the land also affect the shape of a shoreline. Some areas near an ocean or lake boast beautiful shorelines. Do you know any beautiful shores?
Unit 11- Galaxies
Can you believe that there are at least 100 billion galaxies in the universe? Yes, there are! Small galaxies have 10 billion stars, and big galaxies have one trillion stars! The universe must be really big! Do you know what galaxies look like? Some galaxies have elliptical shapes. And some galaxies have spiral shapes. The Milky Way is a spiral galaxy. These two shapes are the most common shapes of galaxies. But some other galaxies have irregular shapes. Can we observe galaxies? Yes, we can see them if we use a really good telescope!
Unit 12- Iron
Iron is a very important element in our lives. It is a kind of metal. Thousands of years ago, people with iron swords and armor were the most powerful people. Now, it is used to build building, machines, and automobiles. Is iron expensive? No, it isn’t. There is a lot of iron in the Earth. Do you know where else we can find iron? In the human body! Like other animals, humans need iron. In human blood, there is iron. If you don’t have enough iron in your blood, you may become very sick!
Unit 13- Dictators
A country is usually governed by many people. Then is there any country governed by one person? Yes, there is. In North Korea, Kim Jungil has absolute power, so no one can object to him. He can do anything he wants in his country. Is he a president? No, he isn’t. Instead, we call him a dictator. A dictator has absolute power and rules a country by force. Is Kim Jungil the only dictator in history? Of course not! There were many dictators in history. Usually dictators were bad people. Adolf Hitler was one of them.
Unit 14 – Wagon Trains
When Americans first moved from the eastern coast to the western coast, there were no airplanes, trains, or automobiles. Then how could they move? They used wagons! Moving from the eastern coast to the western coast was really a long trip. They could meet wild animals or Indians. Or they could get lost. Therefore, the travelers traveled together. They traveled in a straight single line. If you saw them, you might think they looked like a train. So this group of wagons is called a wagon train. At night, they formed a circle with their wagons and took a rest.
Unit 15 – NATO
NATO is the North Atlantic Treaty Organization. It is a kind of contract among Western European countries and North American countries. A few years after World War II, Western European countries, the United States, and Canada wanted to protect themselves from the Soviet Union. So they promised to help one another if one of the NATO countries was in danger. How many countries are members of NATO? There are 26 European countries, and Canada, and the United States. Do you know where the headquarters of NATO are? They are in Belgium.
Unit 16 – History
What is history? It is a written record of human activities over time. Historians discover these records and study history. Then how could we learn about ancient life if there were no written records? Historians also study ancient architecture, drawings, weapons, tombs, and so on. We call the time without any written record ‘prehistory.’ Both prehistoric time and historic time are very important to understand human activities and civilization. Who left the first written records? Chinese people left records on animal bones and shells about 3,300 years ago.
Unit 17 – The French Revolution
In the late 18th century, in France, the economy was in trouble. Why? At that time, Louis XVI became the king of France. The king and the queen Marie=Antoinette did not really care about their country. Instead, they spent a lot of tax money to buy expensive things. Therefore, the economy was really terrible. People couldn’t even buy bread! So they got upset and attacked the palace, Versailles. This event is called the French Revolution. Do you know what happened in France after the French Revolution? France didn’t have any more kings or queens.
Unit 18 – Samurais
Who are Samurais? Samurais were high ranking soldiers in Japan. They wore armor and used swords. First, samurais worked for the upper class. But they governed Japan later. There were a lot of samurais in Japan, and those samurais affected Japanese culture a lot. The cherry blossom is the national flower of Japan, because Japanese people believe it stands for the samurai spirit. Did only Japanese men become a samurai? No, there were some Western samurais, too. If the ruler of Japan allowed it, a Western person could become a samurai.
Unit 19 – Monopoly
When you go to a market, you may find that many companies make similar products. What if there was only one cereal company in your country? We would call it a monopoly. A monopoly means there is no competition in the market. If a company has a monopoly, it can control the price of its product. So people have to buy the product even if it is very expensive! Therefore, governments usually prohibit companies from having a monopoly. So companies compete to make better products and offer cheaper prices!
Unit 20 – Gladiators
Gladiators were fighters in the ancient Roman period. They fought in big stadiums, and people watched their fights for fun. Gladiator fights were the biggest entertainment at that time. Gladiators sometimes fought against each other and sometimes fought with wild animals like lions! Some gladiators were volunteers because they could get a lot of money if they won. However, many of them were slaves from other countries. What happened if they lost? Many gladiators lost their lives or were wounded during fights.
Unit 21 – The Free States
Do you know that there were slaves in the United States? Before the mid 19th century, there were many slaves in the United States. When Abraham Lincoln became the president of the United States, he wanted to free all slaves. The states in the Midwest and Northeastern parts of the United States supported his decision and freed the slaves living in these places. These states were called the free states. How many free states were there? There were 19 free states at the beginning of the Civil War. However, every state became a free state after the war.
Unit 22 – Heavy Industry
Heavy industry describes the companies or factories that make heavy products. Examples of heavy products are automobiles, buildings, ships, and any other product made from metal. In addition, heavy industry also includes companies that make parts of such products, like pipes, machines, or construction equipment. Heavy industrial firms usually need a lot of workers and large machines. So they need a huge area of land. Therefore, you can find cities made just for heavy industry in many countries. If those firms close, many people will lose their jobs!
Unit 23 – Totem
Do you think that animals or plants also have spirits? A long time ago, some people believed that animals and plants had spirits and supernatural powers. These animals and plants were called totems. Can any animal or plant become a totem? Yes, it can. But there should be a group of people who believe in it. Some ancient people also thought their ancestors were animals. For example, one Korean myth tells us that a bear is the ancestor of all Koreans. So we can learn that the bear was a totem for Koreans a long time ago.
Unit 24 – Territory
What is a territory? When a person, an organization, or a nation owns a large piece of land, that land becomes a territory. We don’t call a small land a territory. A territory is often bigger than a small city. So who decides that an area becomes a territory? Usually, people and companies pay money to buy it. Countries sometimes have a war to gain territory. For example, England and France had territories in North America after fighting with Native Americans. Is all land on the Earth a territory? No, it isn’t. No person or country owns Antarctica.
Unit 25 – Whole Numbers
What are whole numbers? Whole numbers are natural numbers and 0. Natural numbers are the numbers when you count something. Thus, whole numbers start from 0. And the next numbers are 1,2,3,4, and so on. What is the rule for whole numbers? First, it should be 0 or bigger than 0. Second, the number doesn’t have a decimal point. For example, 2.5 can’t be a whole number. Third, every whole number has its next whole number. Whole numbers are used to count time, dates, money, and so on.
Unit 26 – Fractions
What is a fraction? In mathematics, a fraction means any part of a number. If you learned division, it must be easier for you to understand a fraction. When you divide 4 by 2, you will get 2. It is because 2 is half of 4. The symbol for a fraction is ’/’. A fraction explains how to count a part of something. Why do we need fractions? Fractions help us get an answer if the result is not a whole number. Then how do we read a fraction? When you see 3/7, you read it “three seventh.”
Unit 27 – Murals
Have you seen any murals? A mural is a picture painted on a wall or ceiling. Do you know the famous work of Michelangelo, The Creation of Adam? It is a mural because it is painted on the ceiling of a chapel. Long, long ago, people lived in caves. They sometimes drew pictures on the walls of caves. Those drawings were the earliest murals in history. Art historians are very interested in murals because murals are the earliest form of art. In addition, murals in prehistoric time help us understand our ancestors.
Unit 28 – Gothic style
About 1200 AD, most Europeans were Christians. So Europeans built many churches. Those churches had pointed arches. Do you know why? They believed they could be near their god if the church was very high. This style of architecture is called the Gothic style. Also, Europeans people were very rich at that time. So they spent a lot of money on building magnificent churches. Therefore, churches in the gothic style are very huge and beautiful. Later, the Gothic style became famous, so people built other buildings in the Gothic style, too.
Unit 29 – Ostinato
Do you know what ostinato is? Ostinato is a short musical phrase. It appears throughout a song. Where can we find ostinato? We can find ostinato both in some popular music and classical music. Usually ostinato is played by the same voice or instrument. Composers sometimes make the rhythm of the phrase change a little bit, but it usually has the same pitch throughout the song. Bass guitars are commonly used to play ostinato. Jazz musicians often use ostinato. When you listen to jazz next time, why don’t you try to find an ostinato in the song?
Unit 30 – Caribbean Folk Music
Around the Caribbean Sea, there are many small island countries, like Jamaica, Puerto Rico, Bahamas, and Haiti. People of these countries are festival lovers. At a festival, they play their traditional instruments, sing, and dance together. For example, a maraca is one of their favorite instruments. A maraca is a coconut shell filled with seeds and beans. If you shake maracas, beans and seeds make a sound. Banjos are also famous. A banjo looks and sounds like a guitar. With those instruments, they play samba or rumba music. And these kinds of music are all good for dancing!