User:Marica.tiboni/Sandbox2

The Earth, as all the planets, is subject to a rotation about its own axis and a surge of revolution around the Sun.

Rotational motion

The Earth's rotation is clockwise (from West to East) around an imaginary axis that passes through the poles. To make a complete rotation on its axis, the Earth takes 24 hours, a time frame called solar day. This movement has some consequences:

• the alternative of day and night, that is a period of light and one of dark;
• apparent diurnal motion of the Sun in the sky, from East to West.
  

  rotation end revolution

The motion of revolution

• the revolution of the Earth takes place on an elliptical orbit, a little squashed, which is covered in about 365 days and 6 hours (a little over a year); the Earth's axis has a constant inclination of 23° to the plane of the orbit.

The most obvious consequences of this motion are:

• the duration of day and night.

The Earth's axis

The Earth's axis is tilted: for this the circle of light does not always passes to the poles. Therefore, at the North Pole you can have 24 hours of darkness. Conversely, the Equator day is always divided into 12 hours of light and 12 hours of darkness: the equator is still halved from the circle of enlightenment. In all intermediate positions on the day will be longer than the night or, vice versa, the longest night of day, depending on the time of year.

The changing of the seasons

The succession of the seasons, that is warmer and colder periods in the year, is due to the constant inclination of the Earth's axis during the revolution. This produces two effects: during certain times of the year, the day is shorter than the night (at other times it is the other way around), with the result that the days are cooler (or warmer) because the Sun heats the surface for a different time; also the Sun's rays come in the same area of land with different inclination in b throughout the year, dispersing in different ways their energy on the surface.

thalassemia

is a genetic disease that comes from the greek (Thalassa "sea" αἷμα, AIMA, "blood") There are different types of thalassemia:Africa alpha thalassemia (reduced alpha chain) synthesis is most prevalent, while in the Mediterranean basin is more widespread beta thalassemia (reduced synthesis of beta chains), called for this also "Mediterranean anemia."