The air all around you and all around the Earth makes up the lower part of our atmosphere. The entire atmosphere is made up of gas molecules, but as you get farther away from the Earth's surface, the types of gases change.
According to the U.S. Environmental Protection Agency, for every dollar spent on the Clean Air Act of 1970, Americans have received a $20 return on health care and pollution savings. In 1990 alone, vehicle and smokestack emission reductions saved an estimated 79,000 lives and resulted in an estimated 15 million fewer respiratory illnesses.
Blowin' in the Wind
Begin your discussion about wind with a simple poem written by Christina Rossetti:
Who Has Seen the Wind
Who has seen the wind?
Neither I nor you.
But when the leaves hang trembling,
The wind is passing through.
Who has seen the wind?
Neither you nor I.
But when the trees bow down their heads,
The wind is passing by.
What makes air move? What makes the wind? Have all the students stand on one side of the room. Then have them all walk across to the other side at the same time. That's what wind does to air molecules, but how? The wind's energy comes from the sun. The sun's rays hit the Earth and warm the air molecules closest to the surface. When that layer of air warms up, it becomes less dense, and it floats higher, allowing cooler air to come back to the ground. That movement creates the wind.
Split the class into two groups. One group should stand on one side of the classroom, which represents the North Pole. The other group should stand on the other side of the room, which represents someplace warm (you can use a globe and let them pick a tropical place) near the equator. The sun's rays warm the equator more than the poles. So what will happen when those air molecules at the equator warm up? They get lighter and are replaced by the cold molecules that are at the poles. Have the children switch places. Now the cold ones are at the equator. What's going to happen to them? They are warming up and the ones at the pole are cooling down. What happens when the ones at the equator warm up? They trade places again. The warm air and cold air are constantly changing places. These are global air currents.
When pollutants end up in the air, they sometimes connect to the water vapor that eventually becomes rain. When the rain or water vapor comes down attached to the pollutant, it creates acid rain. Acid rain is harmful to plants, animals, soil, and water bodies. It's even strong enough to eat away at buildings and statues. Ouch!
Air Currents and Pollution
What happens if one of the places produces a bunch of air pollution? Say the people in the warmer spot build a whole bunch of factories and start driving a lot of cars. Have some of the children in the current warm group hold gray and brown construction-paper clouds that represent air pollution. Except for a very few scientists or explorers, no one else really lives at the poles, and they are probably not making any pollution, so your North Pole group doesn't get clouds. What's going to happen to that pollution, though?
When the air heats up, it trades places with the cold air. The students switch places again. Now the polluted air is far away from where it was made. What's happening in the warm place? More pollution is being made, so give some of your equatorial students some pollution clouds. Then the air heats up and everyone switches places again. Then more pollution is made, more students at the equator are given clouds, and everyone switches again. What's happening? The pollution doesn't go away; it just keeps blowing around. Unfortunately for the polar bears, even though they don't make any pollution, they still have to breathe it.
For thousands of years, people have used wind power. The ancient Egyptians used wind power to sail boats down the Nile, Europeans used windmills to grind wheat and other grains, and American colonists built windmills to pump water up from underground. Right now, most of our energy comes from burning coal and oil, which are nonrenewable resources and will eventually run out. Wind is called a renewable energy source because it will never run out, and it's also a very clean energy source. Mining for coal and drilling for oil create large amounts of pollution, as does burning them. Make your own mini-windmills with a piece of paper, a push pin, a couple small beads, and a dowel or pencil.
Decorate an eight-inch square piece of paper.
Fold the square into a triangle, corner to corner, and then fold again. Open it up and you should have a big X. Make a pencil mark about a third of the way from the center on each line.
Cut along the fold lines, stopping at your pencil marks.
Bring every other point into the center (don't fold) and stick a push pin through all four points in the middle. The head of the push pin becomes the hub of the windmill.
Turn the windmill over to make sure the pin went through the middle. Give it a little wiggle so the hole opens up a bit to ensure the windmill will spin.
Put a couple small beads onto the sharp end of the pin and then stick the pin into a thin dowel or pencil.
Huff and puff and blow the windmill around!