11 A2 the science of heat

CHAPTER 1 It's Too Hot! PUT ON SOME SHORTS AND AT-SHIRT. TURN ON THE AIR CONDITIONING. THIS BOOK IS GOING TO MAKE YOU FEEL HOT! "Good morning everyone, you are listening to XYZ radio. And now the weather. It's going to be a very hot day today, with temperatures of 38 Celsius. Lots of sun and no clouds." Are you happy when you hear this because you love the heat? Or are you unhappy because you hate the heat? The dictionary says that "hot" means having a high temperature. But what does that tell us? Two people are sitting in a room together. One of them is sweating and wants to open the windows. The other is happily reading a book and loves the temperature. Different people feel comfortable at different temperatures. But why?

Well, sometimes your body can make a difference. People who are heavy usually don't like the heat as much as people who are thin. A person's age is also important. Older people usually have more problems when it is hot. They don't sweat as easily or as much as young people. Do men's bodies adapt to the heat better than women's? Yes, men sweat more than women, so they are better at keeping their body temperatures normal when it is hot.

CHAPTER 2 Hot Places MANY PLACES IN THE WORLD ARE SO HOT AND DRY IT IS NEARLY IMPOSSIBLE FOR PEOPLE TO LIVE THERE. Deserts The biggest and perhaps the most famous desert in the world is the Sahara, in Africa. It is about as big as the USA! If you look at a picture of this desert, you might think you are looking at a very big beach. In places like the Sahara, and other hot deserts, there are a lot of sand dunes (some as high as 180 meters) and rocks. There isn't much water in deserts because it doesn't rain much. When it does rain, it often rains very hard, but only for a short time. Because of the hot, dry air, the water quickly evaporates.

The Sahara is the biggest desert in the world, but is it the hottest? Not everyone agrees which is the hottest place in the world. It is difficult to say. Do we mean the highest ever temperature in one day? Or the highest temperature during a year? Or over many years? Let's look at some of the world's hot places. One day in 2008, the Turpan Basin in China had a temperature of 66.8C in the shade! In 2003, the shade temperature in a part of Queensland, Australia, was 69.3C. Think about living in the Lut Desert of Iran. A thermometer there showed a shade temperature of 70.7C in 2005. Nobody could live very long in that temperature! Volcanoes If you think the Lut Desert is hot, what about deep inside the Earth? Scientists say the temperature there is about 7,000C! This is so hot that the rock is not hard, it is a boiling liquid called magma.

Volcanoes are mountains that have a lot of magma below them. There are about 1,500 volcanoes in different countries around the world and there are many more under the sea. Sometimes, the magma below a volcano becomes even hotter and moves towards the top. Suddenly, the top of the volcano breaks open, and thousands of kilograms of boiling magma and ash fly up into the air. This is called a volcanic eruption. Eruptions can be very dangerous. In 1883, a volcano on the island of Krakatoa, in Indonesia, erupted. Almost all of the island fell into the sea and 40,000 people lost their lives. People heard the sound of the eruption thousands of kilometers away.

Mount Vesuvius, in Italy, has erupted many times in the past, most famously in 79 CE when it destroyed the city of Pompeii. In 2011, an underwater volcano erupted near Japan. A tsunami followed minutes after this and killed thousands of people. So it's really hot deep inside the Earth, but it's much hotter in another place. When you are sitting on a beach and the temperature is 38C, do you sometimes think about how hot it is on the Sun? The heat from the Sun travels 150 million kilometers to get to you. In the center of the Sun, it is an amazing 15,000,000C. Now that is hot!