9 A2 the greatest invention of all time

CHAPTER 1 What Is the Greatest Invention SCIENTISTS INVENT NEW THINGS EVERY DAY. SOME OF THESE THINGS BECOME AN IMPORTANT PART OF OUR LIVES. How many of your friends have a cell phone or a laptop? How many of them use the Internet? The answer is probably all of them. We use the Internet to talk to our friends, to buy things, to get information, and to do business. But it's a very modern invention. Many other inventions that are part of our lives were not around 100 or 150 years ago. But it's difficult to imagine life without them.

In this book, you're going to read about some important inventions. Maybe you don't think they're inventions because you use them every day. For example, pipes bring water into our homes. We read books, magazines, and comic books because someone invented a special machine to print them. Imagine life without cars or airplanes, without refrigerators and medicines. They're all inventions. As you read this book, think about this question: "What single invention is the most important to everybody in the world?"

CHAPTER 2 Plumbing WHEN YOU TAKE A BATH OR WASH THE DISHES, DO YOU THINK ABOUT WHERE THE WATER COMES FROM? We have plastic or metal pipes in our houses. These pipes bring clean water from rivers and lakes and take dirty water away. This is plumbing. A long time ago, people didn't have baths or toilets in their houses. They carried water from rivers into their homes. About 4,000 years ago people started building special pipes called aqueducts to bring water to their homes. The ancient Romans were especially good at this. The Ancient Romans knew that dirty water made people sick. They built sewers. Sewer pipes took the dirty water out of the towns.

Thanks to aqueducts, there was plenty of water. The Romans knew that it was important for people to be clean, so they built big baths. In Europe, in the 18th and 19th centuries, thousands of families moved from the countryside into the towns to find work. The towns quickly became big cities. These cities didn't have enough plumbing for so many people. The water in the cities was very dirty. The dirty water ran through the streets and sometimes went into the drinking water. People became sick and died. In the 1800s, cities started to build bigger and better sewers. These sewers carried the dirty water far away. Because of good plumbing and clean water, people became healthier and lived longer.

CHAPTER 3 The Printing Press IN THE 21ST CENTURY, MOST OF US READ BOOKS, NEWSPAPERS, AND MAGAZINES BUT IN THE PAST, ONLY RICH PEOPLE READ BOOKS. In the 15th century, books were very expensive to make and difficult to find. The books were expensive because they took a long time to make. Special workers used pens and pencils to write them on paper made from animal skin. In about 1450, a German man named Johannes Gutenberg had an excellent idea for a machine. This machine could make thousands of books very quickly and very cheaply. He called his machine a printing press. The printing press used metal letters, ink, and paper. This paper was not made from animal skin. It was made from a plant called flax.

Workers put the metal letters together to make words, but they spelled the words backwards— for example, for the word "House" they put "HOUSE". They put all the words next to each other in a short box to make sentences— also backwards. Then they put ink on top of the letters. They pushed, or pressed, paper onto the inked letters, and pulled the paper off very carefully. The words printed on the paper going the right way! Many people in 15th-century Europe couldn't read or write. Most people didn't go to school, and most never saw a book. They didn't need to read because they worked on farms and learned how to do their jobs from other people. But Gutenberg's new machine changed people's lives.