Two Movements of the Earth: Rotation and Revolution
As a solar planet, the Earth revolves around the sun. In addition, it also spins on its own axis. Thus the Earth has two movements: rotation and revolution.
Rotate
The earth rotates on its axis from west to east. Axis is an imaginary line that passes north and south poles. The earth's rotation is complete in about 24 hours - this is called the daily motion of the earth. This motion is responsible for day and night.
One rotation is completed when a celestial body passes the observer meridian's line two times in a row.
How the rotation period is calculated: The rotation period is calculated with reference to the star and with reference to the sun. When calculated with reference to the star, it is called sidereal day and when calculated with reference to the sun, this is called the day of the sun.
Sun day and sidereal day: Day of the sun is a 24 hour period, and the duration of sidereal day is 23 hours 56 minutes. The four minute difference between sun and sidereal days is due to the fact that Earth's position is constantly changing with reference to the sun because of the revolution around it; While referring to unlimited stars, it will remain unchanged. So, sidereal day is the actual time taken by the planet for 360 degree rotation right on its axis.
Due to the apparent motion of the sun, the look of the night sky as seen from the Earth changes from day to day. The stars rise every day, four minutes earlier than the previous day. Also, every night, a degree of celestial sphere is added to the eastern sky while one degree is lost from the western sky.
Earth Rotation
Earth Rotation
The Earth Revolution
The Earth Revolution
Revolution
The movement of the Earth around the sun in its orbit is called a revolution. The movement of the earth is also from west to east. The period of the revolution is one year (365 1/4 days).
Earth's orbit around the sun is elliptical and not circular. Because of this, the distance between Earth and the sun keeps changing.
When this distance is minimum, Earth is said to be in perihelion (about 3 January).
When the distance is maximal, it is said to be in aphelion (around 4th of July).
The average maximum and minimum distance is called the average distance and the sun's distance from the earth is 150 million kilometers.
The true trace of sunlight through the stars remains in space is called the ecliptic, and the imaginary plane that passes through this plane and extends outward through all the dots is called the plane of the ecliptic. This aircraft is imagined horizontally. Earth's axis (rotation axis or pole) makes a 66 1/2 angle to the ecliptic plane.
Earth's axis leads to the same point (polar star) in space. As a consequence of the latitude on the surface of the earth where sunlight drops vertically continues to change as the earth moves its orbit around the sun. Because the earth reaches four critical positions with reference to the sun.
1). Equinoxes: On March 21, Earth is so positioned with reference to sunlight that the vertical sunlight at the equator and the rest of the world experiences the same day and night.
2). Equinox autumn: A similar situation occurred on 23 September.
3). Summer summer turning point: On June 21st, sunlight is vertical above the Tropic of Cancer because the north pole of Earth tends to the maximum toward the sun. At this time, the north pole undergoes a long and continuing day and the south pole continues over night (ergo, which we know as the summer solstice). The northern hemisphere has a current summer and the southern hemisphere is experiencing winter now. Also a day longer than the night in the Northern Hemisphere today.
4). The winter solstice: On December 22, the earth's position corresponds to the sun in such a way that the south pole tends to the maximum toward the sun and the Tropic of Cancer receives the sun's vertical rays. This position is called the winter solstice as the sun shines continuously in the south polar region and is a continuous night in the north pole. It is winter in the northern hemisphere and summer in the southern hemisphere. During the winter solstice, the days are longer than the night in the southern hemisphere.
- Thus, the variations in the duration of day and night and the turn of the seasons are caused by the earth's revolution and the earth's shaft tendency. Also the seasons are reversed from the northern hemisphere to the southern hemisphere.
Midnight Sun
At the time of the summer solstice, there is a continuous day in the north pole as the illumination circle passes over the Arctic Circle beyond the poles. Consequently, in places outside the Arctic Circle, the sun will be seen continuously even at night in the same longitude at the lower latitudes. This phenomenon is called midnight sun. Comparable situations occur in the Antarctic Circle during the winter solstice when the illumination circle passes this circle beyond the south pole.