sábado, 10 de septiembre de 2011

Movements of the Earth

The earth is not static, it moves steadily through space, following two movements:

Rotation Movement:  : It is the one which describes the Earth spinning around an imaginary axis, eastbound.
The axis of rotation is tilted with respect to the plane of the orbit that describes the Earth around the sun.
The rotary motion produces a succession of day and night, as well as the time difference between some areas of the Earth.
As the Earth is spherical it is only illuminated on the face opposite to the sun. As it is turning on itself, the lighted face is not always the same. So the illuminated part (day) and the dark part (night) are constantly shifting.
Principal consequences of the rotation movement:

                                      * Day and the night
                                      * A uniform insolation of the Earth.

Translation movement:It is the one that the Earth accomplishes around the Sun. It describes an elliptical orbit of 93 million km, maintaining a speed of 29.8 km / seconds.

A Year: In this tour the Earth spends 365 days and 6 hours. Those 6 hours which are accumulated each year, after 4 years, they are 24 (one day). Each four years there is one that has 366 days, called leap year.
The plane that determines the Earth's orbit is called the ecliptic circle and is the maximum that the Earth describes in its movement around the Sun.
The Seasons: The translation movement causes the four seasons.The stations are determined by the tilt of the earth's axis on the ecliptic. According to the position of the sun-earth connection, some areas receive more solar radiation than others.
The Change of Seasons:  Seasons are changing alternately by the hemisphere which is closer to the sun. When the northern hemisphere is the farthest from the sun, it will be winter, while simultaneously, the southern hemisphere is closer and then it is summer there.
There are 4 key positions in the movement of translation: Spring and Autumn (equinoxes) and Summer and Winter (solstices). 


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