THE EARTH

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ContentsI. Our WorldII. The AtmosphereIII. Time and SeasonsIV. Weather and Climate

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Our World

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The Earth formed about 4600 million years ago.4600 million years ago.

The equatorial diameter of Earth is 12,757 12,757 kilometers.kilometers.

Weigh nearly 6000 6000 million million million tonnes.

The land covers 29% of the Earth’s surface.

71% is covers by the oceans and seas.

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Inside the Earth1st layer call Crust .Crust . it is about 6 km deep to Oceans.

2nd layer call Mantle.Mantle.

3rd layer call Outer core.Outer core. 4th layer call Inner core.Inner core.5000 kilometers .5000 kilometers .Temperature is 2800 Temperature is 2800 ooC.C.

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What are latitude and longitude? • latitude and longitude are the lines marked on a map or

globe of the world.

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Why is the world round?Why is the world round?• When the Earth formed, it was hot and liquid.

• It become round because it was floating in space.

• When the liquid rock cooled and hardened into solid rock, the Earth stayed round.

The AtmosphereThe Atmosphere

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What is air made of ?How much does air weigh?

Air is made of invisible gases.Air is made of invisible gases.You cannot see the gases, but you can feel them when the wind blows.

There is about 160 kilometers of air above our head.

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Why is the sky blue?Why is the sky red at

sunset?

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During the day, light from the sun travels through the air to reach our eyes.

The white light of the Sun in fact consists of a mixture of colors (colors of the rainbow)

The blue rays are scattered by the air and come to our eyes from all angles in the sky. This makes the sky look blue.

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As the sun begins to set, the light must travel farther through the atmosphere before it gets to you.

More of the light is reflected and scattered. As less reaches you directly, the sun appears less bright. The color of the sun itself appears to change, first to orange and then to red.

This is because even more of the short wavelength blues and greens are now scattered.

Only the longer wavelengths are left in the direct beam that reaches your eyes.

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The sky around the setting sun may take on many colors. The most spectacular shows occur when the air contains many small particles of dust or water.

These particles reflect light in all directions. Then, as some of the light heads towards you, different amounts of the shorter wavelength colors are scattered out.

You see the longer wavelengths, and the sky appears red, pink or orange.

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How many colors are there in a rainbow?Can we see rainbow at night?Where does a rainbow end?

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Rainbows colors are:Violent light, indigo, blue, green, yellow, orange, red.

You can be seen rainbows at night. (MoonlightMoonlight)

Rainbows form in falling rain and in clouds of spray when sunlight falls on them. So, the rainbows is as far a way from you as the rain or spray . To see a rainbow, the Sun must be behind you.

Time and SeasonsTime and Seasons

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Why do we have seasons ever year?

Can the same day be both the longest and shortest day of the

year?

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Weather and Climate

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Why does rain fall from the sky?

Why does lighting strike?A flash of lighting is a huge spark of electricity.During a thunderstorm, electric charges of millions of volts

build up in the clouds.Electric charges build up on the ground too.

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How far away is thunder and lighting?

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Thanks

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