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Amazing facts
Why is the centre of the Earth hot?
Some scientists believe that the earth began billions of years ago as a huge ball of swirling dust and gases. As the earth grew larger, new materials piled up on the outside and squeezed the materials inside. Energy from all this activity was released as heat. Eventually most of the iron in the earth melted and collected at the core, or the centre. This released more heat. The temperature at the core rises — perhaps more than 9000°F (4,982°C). Lighter materials rose to the outside of the earth and cooled, forming the earth’s crust.
Why does snow stay on mountain top?
Since the top of the mountain is closer to the sun than the base, the peak should be warm and toasty, right? Actually, the top is the mountain’s coldest spot. Here’s why: the dense atmosphere near the base easily traps the sun rays. But the thinner atmosphere near the peak traps less heat, and the temperature gets colder and colder the higher you go. Above a certain point called the snow line, snow never melts. So when it comes to the mountain, snow doesn’t mean winter.
Why do I feel hotter when I wear dark colours?
Dark colours tend to absorb light energy. Light colours and white reflect light energy. That’s why you might feel warmer wearing a dark-coloured jacket than a light-coloured one. When light shines on your dark jacket, the jacket fabric absorbs light energy. The absorbed light energy causes the electrons in the atoms of the jacket to vibrate. This activity releases heat energy, which makes the jacket — and you — warmer. That’s why people tend to wear more dark colours in winter and more light colours in summer.
Why does the wind blow?
Whoosh! You know that wind is moving air. But what causes the air to move? It’s the uneven heating of the earth’s atmosphere. As the sun warms the earth’s surface, the atmosphere warms too. Some parts of the earth receive direct rays from the sun throughout the year and are always warm. Other places receive indirect rays, so the climate is colder. Warm air, which weighs less than cool air, rises. Then cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow.
Why do clouds float?
Clouds may seem to defy gravity because they float, but gravity does affect clouds. Gravity influences the shapes and sizes of clouds and causes snow and rain to fall from them. Clouds form from water that evaporates from lakes, rivers, oceans and soil. When warm air and sun cause evaporation the warm air, full of water vapour, rises. As air rises, it expands and cools, forming clouds. Cooler air can’t hold as much water vapours as warm air. The extra vapour changes into water droplets and ice crystals which gravity pulls to earth as rain and snow.
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