In the time that the Earth revolves around the same moves and moves around the sun . And its place in 365 days , 5 hours , 48 minutes and 51 seconds almost any in about 365 days and a quarter . This is what used to be called " the year ." And the direction of rotation of the Earth around the sun is like all the other planets of the solar system from west to east , but we are not aware of this movement is really going on , but at face value the reverse , Vijal us that the sun is orbiting in the opposite direction . And called the itinerary of the Earth travels around the sun in the orbit of the Earth or the Earth's orbit . This orbit is not a circle sense of the word , but rather oval-shaped elliptical any ELLIPSE.
And not the Earth rotates on a vertical elliptical orbit any Ptaamd centered on the level of the polar orbit and it diagonally so that deviates from the axis of the poles positioned vertically by 23, 27 and departs from the level of the Earth's orbit by 66 , 32 and 45
And maintains the stability of the Earth's axis inclination and direction during the rotation of the Earth around the sun occurring among a polar Earth toward the sun , while the other is moving away from it ( see Figure 4 or 7) . And when the Arctic heading toward the sun exposed the bulk of the Northern Hemisphere to sunlight Vitoul day and short night and this happens in the summer. In the southern hemisphere, where the South Pole is moving away from the sun Vitoul night and shortens the day and the opposite happens in the winter .
Relay day and night and contrast Toulhma :
To follow the night and day is the direct result of the spherical Earth and spins around its axis in front of the sun once every day . But if we assume that the Earth's axis is on a diagonal plane of its orbit , but it perpendicular to the length of night and day of equal length consistently throughout the year because the sun's rays will arrive perpendicular to the ground in the various stages of its movement on the orbit. Therefore, the inclination of Earth's axis on the plane of its orbit is responsible for the variation that you know the length of day and night in all performances except the area of the equator , which is equal Toulhma it throughout the year . With the exception of this region , we find that the length of the day over the summer is always the length of the night while increasing the length of the winter night on the length of his day in all the world .
And the difference between them is increasing gradually during the summer as we get closer to the summer solstice day during the winter and the closer to the winter solstice day . Therefore, the longest day and the shortest night of the year Ikunan on June 21 in the northern hemisphere and is the date of the summer solstice , while the shortest day and longest night of the same in the northern hemisphere on Dec. 21 and the date of the winter solstice .
And increasing the difference between night and day whenever gradually after us from the equator toward the poles. On the day of the summer solstice , for example, the length of the day at the equator , and more than 12 hours to 15 hours at latitude 40 north and 20 hours at a latitude of 63 , and 24 hours at the Arctic Circle , which is today then the whole day . Then increasing the number of days that are all day until you reach a full month at a latitude of 67 and four Ochehrand latitude 68 and then six months at the North Pole itself , and at this time have the Arctic as soon put him to the sun and is going on and the area surrounding it constantly in sunlight , while the South Pole in putting him farther it is Fedor and the surrounding area are constantly in the region not reached by sunlight throughout the six months , and just the opposite happens in the winter.
And which has already become clear to us the following facts :
- That night and day are entitled to equal Toulhma at the equator throughout the year .
- And also are entitled to equal at all points of the ground when the sun lying directly above the equator .
- That the difference between Tolehma few among orbits
- Maximizes the difference between Tolehma whenever we went north or south away from the tropics
- The maximum length ranges of the night or day in the polar regions between the 24 hours when the polar circles and six months at the poles .
Four Seasons :
When we look for the Figure ( 4) shows that the conditions of the Earth in its orbit around the sun at the equinox and my time and my time coups note the following:
- In the fall on March 21, the sun is perpendicular to the equator Viadel mile rays on the hemispheres , Visawy them day and night , as the two equalized heat. And then begins to spring in the northern hemisphere , and autumn in the southern half .
- On September 23, in the fall sunshine again perpendicular to the equator , Viadel mile rays on the hemispheres , and equal to them day and night , as the two equalized heat. , And then begins to fall in the northern hemisphere and spring in the southern half . This spring and is known to separate the transition from summer to winter .
- On 21 June the sun's rays fall perpendicular to the Tropic of Cancer , which is located on latitude 23 and 27 north of the equator and from there be sunlight highly inclined to the northern hemisphere and a weak tendency to the southern half , with the passage of the day and the temperature rises in the second half northern , and shortens the day and temperatures drop in the southern half , and therefore eliminates the summer in the northern hemisphere , and winter in the southern half .
- In the fall on December 21, the sun is perpendicular to the Tropic of Capricorn located on latitude 23 and 27 south of the equator , and there is a tendency weak rays fall on the northern hemisphere and a strong attraction on the southern half Fiksr day and temperatures drop in the northern hemisphere , and lengthens the night and the temperature rises in the southern hemisphere , and so it is winter in the northern hemisphere , and summer in the southern half .
This spring and starts from March 21 to June 21 , and the summer of June 21 until September 23 , and the fall from September 23 until March 21.
Belt perpendicular sunlight
Given the tendency of the Earth's axis and Taamayor not at the level of the point of its orbit , and the Earth's rotation around itself and around the sun on the other hand , lying directly above the places where the sun does not remain constant. And this is orthogonal gradually and regularly during the year, will move from south to north and from north to south in the area or the northern belt alone is the Tropic of Cancer and the Tropic of Capricorn south alone , .and occurs perpendicular sunlight on the Tropic of Cancer and the Tropic of Capricorn once a year while going twice in the area bounded between them .