Earth
From the Simple English Wikipedia, the free encyclopedia that anyone can change
Earth is the planet that humans, animals and plants live on. It has only one moon. Earth circles around the Sun every 365.2564 days, known to us as one earth year. The Sun provides light that shines onto the Earth.
The Earth is a spheroid, a shape which is not quite a sphere. It spins (turns around itself) from west to east so each part of it is in light during the day and dark at night. Just the right amount of heat from the Sun reaches Earth to keep its water from freezing, but not enough to turn it all into steam.
Around 71% of the Earth's surface is covered by salt water in its oceans. It has seven continents which rise above the oceans to make land, while one (Antarctica), is covered almost completely by ice, with very little land above the ice. There are also a lot of smaller islands.
The Earth's north and south pole are very cold and full of ice because they get less sunlight than other areas.
The heat from the Sun makes the ocean waters turn into water vapour to make clouds. Clouds help protect the earth from harmful ultraviolet rays from the sun. When there are too many clouds in one place, rain falls. The water vapour changes back into water and falls back on the land, to form many rivers which have shaped it.
The Earth is the only place humans know about which has life. The Earth's liquid water makes life possible. The places with the smallest amount of rain are called deserts.
The Earth is tilted (that means that it is turned a little bit onto its side) as it goes around the Sun. This means that at one time of year the north pole gets more of the Sun's heat, and six months later the south pole gets more. This also makes the four seasons of summer, autumn, winter, and spring.
The Earth has mountain ranges and volcanoes. They are caused by movement of hot rocks deep inside the Earth. When the rocks move, there are sometimes earthquakes that shake the ground.
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[change] The Earth's Beginnings
No one knows for sure how the Earth was formed, but the best possible idea that scientists have (called a "theory") is that the Earth was formed from a flat circle of gas and dust around 4.55 billion years ago, and that gravity (the force that holds everything together) pulled the gas into a bigger and bigger ball of molten rock that cooled down very slowly over millions of years. According to this idea, heavy materials sank deeper into the ball to form a core (centre) of dense hot rock mostly made of iron. Less dense materials stayed on the surface and cooled to form a solid rocky crust (outside layer). Gases outside the crust formed the air.
Scientists also think that later, another planet as big as Mars smashed into Earth and big pieces of it were sent flying into space. This would mean that the Earth was destroyed and turned back into molten rock. They think that after the planets smashed into each other, many small pieces of rock and dust circled the Earth to form rings that slowly stuck together and became the moon.
If this is true, the moon would have been much closer to the Earth in those days than it is today, and the Earth also would have spun faster so the length of the days were shorter (less than 10 hours). Some scientists also believe that early life had already started on Earth before the smash, but was nearly killed by it. This crash would mean similar ages for the moon and the Earth. It would also explain why the moon has no iron center.
When the Earth cooled down to below 100 °C (212 °F), steam in the air (or atmosphere) started to fall as rain. The water filled up cracks in the solid crust to form rivers, lakes, and oceans on the surface of the Earth.
There are also many other stories about how the Earth began that are different from this one called creation myths. Religions also have different ideas about how the Earth was made.
[change] The Earth's Future
The sun is expected to shine steadily for another billion years before it starts to get bigger. In about 4.6 billion years sun will become a giant star. When this happens the Earth would be big enough to be swallowed up by the Sun. Earlier scientists predict that the Earth might not be swallowed up, since the fraction of loss might bring Earth's orbit to 1.7 AU, if without the tidal interaction. However; even if this is the case we will no longer be able to live on it as all the water would have evaporated, and most of its atmosphere would have been lost. The new scientist calculate due to the tidal interactions with sun and Earth; Earth would be swallowed up by sun anyways no matter what condition.
[change] The structure of the Earth
The Earth is made up of three layers: the core, the mantle and the crust. The innermost layer is the core. The layer surrounding the core is called the mantle. The crust is the outermost layer. The crust is the thinnest layer out of the three.
[change] See also
[change] Other websites
- http://www.solarviews.com/eng/earth.htm
- http://www.earth.nasa.gov/science/questions.html
- http://www.geody.com/
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| The Sun · Mercury · Venus · Earth · Mars · Ceres · Jupiter · Saturn · Uranus · Neptune · Pluto · Eris |
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Planets · Dwarf planets · Moons: Terrestrial · Martian · Jovian · Saturnian · Uranian · Neptunian · Plutonian · Eridian
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Small bodies: Meteoroids · Asteroids/Asteroid moons (Asteroid belt) · Centaurs · TNOs (Kuiper belt/Scattered disc) · Comets (Oort cloud)
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| See also: List of solar system objects |
