Wind And What It Does (1963)

[Music] do you know what makes this big Paddle Wheel on the windmill turn can you tell what makes this wheel [Music] turn as the wheel turns it moves this water pump [Music] the faster the wheel turns the more water it pumps by turning the wheel the wind does work for us the wind can do work in other ways it can push a sailboat across the lake or lift a kite High into the sky yes the the wind can do work for us but how much work it can do depends on the force with which it blows what is [Music] wind although we can't actually see the wind we can see some of the things it does here we can see wind blowing away the smoke as it comes out of the chimney wind is air that is moving what causes air to move this pin wheel spins like the wheel on the windmill when air blows against it the force of the moving air turns the wheel now watch the wheel what makes the pin wheel turn when it's held over the burning candle it must be the force of air pushing against the wheel but where does the moving air come from does heat have something to do with it instead of a candle let's try something else that is hot this time we'll use an electric hot plate these electric coils make the air above the hot plate very warm now when we hold our pin wheel over the hot plate it turns again if we take it away it stops turning this Shadow photograph of the hot plate will help us explain why it actually shows the heated air moving upward now can you tell what makes our pin wheel turn it turns because the heated air that we have just seen moving up Acts just like wind the heated air moves against the wheel forcing it to spin round and round we can see that warm air moves up while cool air moves down to replace the warm air in the same way the air above our Earth behaves like the air above the hot plate warm air moves up and cool air moves down now suppose that you could look at our Earth from far out in space you would see that it was round like a ball surrounded by a layer of air because the Rays of the sun shining on the Earth are more direct at the equator than at the North or South Poles the Earth becomes warmer at the equator than at the poles in this way the air above the equator becomes warmer than the air above the Earth's poles this means that the warm air above the equator will move up away from the earth while the cool air above the Earth's poles will move down toward the Earth in this way a current of air moves above the Earth and this moving air is what we call wind this is how the currents of air above the Earth would look if the Earth were not spinning but remember our Earth is spinning in space and this spinning causes the currents of air to move about something like this this is why in certain parts of the world steady winds blow in the same direction most of the time long ago sailing ships took advantage of these regular winds to carry them across the oceans because the force of the wind is important we often need to measure wind one way we can measure the wind is by observing what it does a light wind barely moves the flag but a light wind may increase to a stronger wind wind the faster the wind the more powerful it is very strong winds are called Gale winds one type of very strong wind is a hurricane a hurricane is a storm with Winds of great force another kind of wind which is very strong and dangerous is called a t tornado this narrow whirling funnel of wind can leave a trail of Destruction many miles long now do you see how great the force of the wind can be we already know something about the force of wind in sailing strong winds can cause such such huge waves that a ship may have to change its course boats and ships must know both the direction and the speed of the wind in order to sail safely airplane pilots need to know about the wind too a strong wind might Force an airplane many miles off its course in order to make proper Corrections for the effects of wind a pilot and his crew must know the speed and direction of the wind when they are flying every airport has instruments for measuring the speed and direction of the wind this instrument is called a wind vein it shows from which direction the wind is blowing the wind vein is connected to this scale which indicat Ates accurately the direction of the wind this instrument is called an anemometer it measures the speed of the wind as the wind spins these cups around the anemometer registers the speed of the wind on this scale knowing about wind helps us forecast the weather too the wind moves clouds and clouds often bring rain or snow weathermen use balloons to learn more about winds that blow very high above the ground as the weather balloon Rises a small radio attached to the balloon sends back signals to the weather station this information often helps weathermen forecast our weather the study of moving air or wind is important in another way sometimes the wind picks up and blows so much sand and dust that we call it a dust storm dust storms sometimes entirely cover houses or Farms this is just one of the ways in which the powerful effect of the wind can change the surface of our Earth all of the time the wind blows somewhere on Earth the force of the wind can do work for us wind brings us our weather sometimes it can be dangerous but most of the time it blows gently and refreshingly bending the branches of trees or just helping us have fun [Music]