Bill Nye: The Science Guy

Wind (2x2)

: 25, 1994

Some answers, my friend, do in fact, blow in the wind. A cool breeze is great on a hot summer day. A cold winter wind can chill you until you can't stop shivering. Where does all that wind come from? It starts with the Sun. Energy from the Sun warms the Earth and the atmosphere, the air, above it. As the world turns into darkness each night, the atmosphere cools off. The molecules in a mass of warm air are more spread out than the molecules of air in a cold air mass. So cold air is heavier than warm air. Cool air masses squeeze warm air up. That's why you may hear people say, "Warm air rises." The Sun warms the Earth with huge amounts of heat each day. And, the Earth is spinning. So, as air masses move up and down, they get nudged sideways along the Earth's surface at the same time. Try drawing a straight line on a spinning ball. It'll curve. The same thing happens to make wind. Air travels all over the Earth moving across deserts, up and down mountains, through val