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Earth...our birth place

Posted: Tue Aug 04, 2009 5:55 pm
by bentley
(Picture - Fotosearch)

Earth, our home planet, is the only planet in our solar system known to harbor life.
All of the things we need to survive are provided under a thin layer of atmosphere that separates us from the uninhabitable void of space.
Earth is a complex and unpredictable planet that has numerous characteristics that makes it different to any other planet...air, water, land, and life—plants, insects,animals and humans.
All these aspects create a constantly changing world that we are striving to understand.

Viewing Earth from the unique perspective of space provides the opportunity to see Earth as a whole. Scientists around the world have discovered many things about our planet by working together and sharing their findings.

Some facts are well known.
For instance, Earth is the third planet from the sun and the fifth largest in the solar system.
Earth's diameter is just a few hundred kilometers larger than that of Venus.
The four seasons are a result of Earth's axis of rotation being tilted more than 23 degrees.

Oceans at least 2.5 miles (4 kilometers) deep cover nearly 70 percent of Earth's surface.
Fresh water exists in the liquid phase only within a narrow temperature span (32 to 212 degrees Fahrenheit/ 0 to 100 degrees Celsius).
This temperature span is especially narrow when contrasted with the full range of temperatures found within the solar system.
The presence and distribution of water vapor in the atmosphere is responsible for much of Earth's weather.

The protective atmosphere

Near the surface, an ocean of air that consists of 78 percent nitrogen, 21 percent oxygen, and 1 percent other ingredients envelops us.
This atmosphere affects Earth's long-term climate and short-term local weather; shields us from nearly all harmful radiation coming from the sun; and protects us from meteors as well.
Satellites have revealed that the upper atmosphere actually swells by day and contracts by night due to solar activity.

Our planet's rapid spin and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape.
The solar wind is a stream of charged particles continuously ejected from the sun.
The magnetic field does not fade off into space, but has definite boundaries. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles.
These air molecules then begin to glow and are known as the auroras, or the Northern and Southern Lights.

The Atmosphere...earths protector

Posted: Sat Aug 15, 2009 12:40 pm
by bentley
Without the atmosphere earth would be nothing but a planet similar to as we know it and all it's splenders would not exist.

It is more than just the air we's a buffer that keeps us from being hammered by meteorites, a screen keeping out deadly radiation and allows radio waves to be sent long distances around the planet.
The air that sets all of this into action is composed of five major layers.

The Troposhpere
The lowest, which is the layer that provides most of our weather & contains aproxamately four-fifths of the Earth's air, it extends only to a height of +/- 11 miles (17 kilometers) at the Equator and somewhat less at the Poles.
The name derives from a Greek word that refers to mixing, this is exactly what happens within the troposphere. As warm air rises it forms clouds and produces rain fall and in turn creates winds to stir the lands below. Typically, the higher you go into the troposphere, the colder it gets.

The Stratoshpere
Above the troposphere is the stratosphere which extends to a height of +/- 30 miles (50 kilometers) and includes the ozone layer, which blocks out most of the sun's harmful ultraviolet rays.
This layer is warmer than the troposphere because of the energy from the ultraviolet light absorbed by the ozone. At its base of the stratosphere it is extremely cold, aproxamately -110 degrees Fahrenheit (-80 degrees Celsius) and towards its top, the temperature would have risen back to a stage of freezing point.

The Mesoshpere
In this layer the air temperature drops again, down to nearly -180 degrees Fahrenheit (-120 degrees Celsius) at the top. Meteors generally burn up in at this point and would disintergrate like a drop of water on a piping hot stove element. It extends to a height of +/- 52 miles (85 kilometers). This is why the Earth's surface isn't pocked with meteor craters, like the moon's.

The Ionoshpere
Is where we would be entering Outer Space, it extends to about 430 miles (690 kilometers) and is so thin it's generally considered part of outer space. The International Space Station and many satellites orbit within this section of the atmoshpere and quite venerable to meteors but are avoided due to constant monitoring.

The ionosphere is named for the ions created within this layer by energetic particles from sunlight and outer space. The ions create an electrical layer that reflects radio waves, allowing radio messages to be sent across oceans in the days before communication satellites. Electrical displays in the ionosphere also create the auroras called the Northern and Southern Lights.

The Exoshpere
Beyond the ionosphere lies the exosphere, tenuous portion of the Earth's atmosphere which extends outward until it interacts with the solar wind. The Solar storms / winds compress the exosphere, when the sun is tranquil, this layer extends further outward like a balloon being released then inflated, constantly. Its top ranges from 620 miles (1,000 kilometers) to 6,214 miles (10,000 kilometers) above the surface and merges with interplanetary space.