Category Physics

How do you explain wind?

Wind

When the air seems calm, and you can’t feel a wind, it doesn’t mean that the wind has stopped blowing everywhere. There are always many winds keeping the air around the earth moving. In one place, there may be a soft breeze from the north. In another place, there may be strong gusts from the south.

Two different winds may blow near the same area at once. Near the ground, one wind may be pushing flags in one direction. But higher in the sky, another wind may be making the clouds scurry in another direction.

The fastest winds are high above the clouds, several kilometres up into the sky. These winds are called jet streams. Often, jet streams are connected. They form one huge, rushing river of wind that circles the earth, sometimes at speeds of more than 320 kilometres an hour. When an aeroplane takes off for a long trip, the pilot may fly into the jet stream because it can give the plane a powerful push.

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What makes the wind blow?

The wind moves over the land. It sways the tall grass in meadows and rustles leaves on trees. It ruffles your hair. In a storm, it whirls and roars. Wind can change a cloudy day into a sunny one by pushing clouds along. Wind is moving air. And it is the sun that makes air move.

The earth spins around like a big top. As it spins, each part of the earth, in turn, comes into the sunlight. The sun’s light warms the earth, and the earth warms the air. The heat makes the molecules of gas in the air move faster and spread apart. This warm air rises up like a big, invisible cloud. It rises because warm air weighs less than cool air.

As the warm air rises, cool air from other places flows in to replace the warm air. This moving cool air is the wind. When you feel the wind blow, you are feeling the movement of cooler air pushing in to take the place of the warm air that rose up into the sky.

What happens to the warm air? It cools and then sinks back to the ground. There it takes the place of warmer air, and all the same changes happen over again!

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What is air made of?

Air doesn’t seem to be made of anything. It has no colour, taste, or smell, and you can see right through it. But air is made up of things. It is made of many kinds of gases. And these gases are made up of tiny bits called molecules.

Actually, everything on the earth is made up of molecules. Solid things, such as plants, animals, and rocks, are made of molecules. So are liquids, such as water, and gases, such as the ones in air.

In solids, the molecules are packed close together and hardly move. In liquids, the molecules are further apart and move faster. In gases, the molecules are very far apart and zip about rapidly. That’s why gases are so light that you can’t see them.

For us, the most important gas in the air is oxygen. We breathe to get oxygen into our bodies. Almost every kind of animal and plant in the world must have oxygen, or it will die.

Only about one-fifth of the air is made up of oxygen. Most of the air – nearly four-fifths – is nitrogen. The rest of the air is made up of many different gases. Water vapour and dust float in the air, but they are not part of the air.

If air is just floating gases, why doesn’t it float away into space? Because the earth’s gravity pulls at the air just as it pulls at you. The air can no more float off into space than you can!

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What colour is the sky?

If you could stand on the moon and look at the sky, it would always be dark black. This is because the moon has no air. If the earth had no atmosphere, our sky would stay dark, too. Instead, the sky over the earth is dark only at night when the sun doesn’t shine.

Sunlight is made up of red, orange, yellow, green, blue, indigo, and violet light. These colours scatter when they hit the earth’s air. Some of them scatter more than others. Red, orange, and yellow light scatter the least. Blue scatters so much that it spreads to fill the sky.

That line in the distance where the sky seems to meet the earth is called the horizon. When the sun is near the horizon, sunlight must travel further through our atmosphere. This makes blue and most other colours scatter too much to be seen. But red, orange, and yellow are scattered just enough to make a beautiful sunrise or sunset. Dust from pollution, forest fires, and volcanoes can help make a brighter red or orange sunrise or sunset. The dust makes the other colours scatter even more.

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What surrounds the Earth?

 

 

Long ago, people believed the sky was a roof that stretched over the earth. Today, we know that a thick layer of air surrounds the earth like the skin on an orange. But unlike an orange skin, the air moves around the earth, and it reaches far above the earth’s surface. This moving cover of air is a mixture of gases called the earth’s atmosphere.

Air covers the earth everywhere. The pull of gravity holds it there. Near the earth, the air is thick, or heavy. Further away from the earth, the air becomes thinner. Furthest away from the earth’s surface, the air thins and disappears altogether. Where this happens is where space begins!

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Who studies the waters?

Many scientists study the ocean, looking into the secrets of the sea. They study how the ocean moves and how it affects the atmosphere. They study the living things in the sea and the shape of the ocean floor.

Scientists who study the ocean are called oceanographers. Sometimes they work aboard ships. Some wear diving suits and air tanks to explore underwater. Others use small submarines. They use underwater cameras to take pictures of the ocean’s floor and the plants and animals that live in the ocean.

Sometimes they use robots to bring up samples of the mud and sand for study. Some scientists study the direction and strength of waves, tides, and currents.

Oceanographers called marine biologists study the plants, fish, and animals that live in the ocean, lakes, and rivers. They keep track of their health and the way they grow.

Oceanographers called seismologists study earthquakes that happen on the ocean floor. One cause of earthquakes is volcano eruptions, so seismologists often keep track of volcanic activity.

Picture Credit : Google