1. Earth Rotation
Rotation of the Earth on its axis is called rotation of the Earth. For a single rotation, the Earth takes one day 23 hours 56 minutes or rounded to 24 hours. Earth rotates from west to east, the rotational motion of the earth causes various events, among others:
The occurrence of day and night
At the moment not all parts of the earth rotating the sun. Part of the earth that gets afternoon sun experience, while the part of the earth who do not get to experience the evening sunlight.
Apparent motion Daily Matahahari
The sun always rises in the east and sets in the west. Movement is called daily apparent motion of the sun. This movement occurs because of the rotation of the Earth. Earth rotates to the direction of movement from west to east. As a result, as if the sun moves from east to west.
The time difference in Different Places in the World
Rotation of the Earth causes the difference in time in various places in the world. In a single rotation, the Earth takes 24 hours (one day) and travel as far as 360 ° angle. Accordingly, any place on Earth at a distance of 15 ° has a time difference of one hour. If the distance is 30 °, then the two-hour time difference, and so on. This figure is derived by dividing the angle traveled by the travel time (360 °: 24 = 15 °). Indonesia lies between 95 ° E and 141 ° E. That is, the length of Indonesia is 46 °. Because every distance of 15 ° difference in time one hour, then Indonesia has three time zones. Three regions such time that Western Indonesia Time (WIB), AM (Central Indonesia Time), and WIT (East Indonesia Time).
Greenwich, London, England lies on the longitude 0 °. Therefore, the time in the city is used as a benchmark for the whole world. This time the benchmark is called Greenwich Mean Time (GMT). With reference to standard GMT, the faster Western Indonesian Time seven hours from GMT. Meanwhile, Central Indonesia Time quicker eight hours from GMT. The East Indonesia Time quicker nine hours from GMT. For example, if the show at 01.00 GMT, the West Indonesia Time showed 08.00.
Gravity Acceleration difference in Earth's surface
Rotation of the Earth causes the Earth is not perfectly round. Earth oblate at the poles. This resulted form the radius of Earth in the polar regions and the equator is different. Differences radius of the Earth makes a difference acceleration of gravity at the Earth's surface. The difference is mainly in the area of ??equator and the poles.
2. Revolution Earth
In addition to spinning on its axis, the Earth also rotates around the sun. The movement of the Earth around the Sun is called the revolution of the Earth. For one revolution, the Earth takes one year (365¼ days). Earth Revolution brought some influence on the Earth. Among them are the following:
Earth around the Sun at an angle of 23½ ° to the northeast of the Earth's axis. This position led to the change of seasons. When the south pole of the Earth gravitate to the Sun, the southern hemisphere to grow closer to the sun. This leads to the southern hemisphere experiences summer. At the same time, the northern hemisphere is getting away from the sun. Northern hemisphere experience winter. Among turn summer into the cold, in the fall. Among turn winter into summer, there was a spring. Thus, the southern and northern hemisphere experienced four musim.Kalian certainly know we lived on the equator, equatorial always receive sunlight throughout the year. Therefore, the equatorial region experienced two seasons, musi dry and rainy season. Teradi rainy season between the months of October to April, and the dry season between the months of April to October. Commonly called the equatorial region of the tropics.
Annual Apparent motion of the Sun
The sun seemed to rise from a different place every certain period of the year. In fact, the Sun actually has not changed position. This appearance is due to the revolution of the Earth. The sun as if to move or migrate. Well, the motion is called the annual apparent motion of the sun. Note the picture below:
March 21. Viewed from Earth, the Sun exactly on the equator (0 °). Therefore, as if the sun rises just to the east. Similarly, as if the sun sank in the west right.
Dated June 21, seen from Earth, the Sun appears to be in northern latitudes 23½º (LU). Therefore, as if the sun rises slightly shifted to the north.
September 23, observed from Earth, the Sun looks back at the equatorial line. As a result, as if the sun rises just to the east.
December 22, the sun appears to be in the southern latitude 23½º (LS) when viewed from Earth. This causes the sun as though rising slightly shifted to the south.
Months have two kinds of movement, ie rotation and revolution. Consequences caused by the rotation and revolution of the Moon are as follows:
Rotation of the Moon on its axis is called rotation of the Moon. For a single rotation, the Moon takes a month (29½ days). The rotation of the Moon does not give any influence on life on Earth.
As the Earth's satellite, the Moon moves around the Earth. The movement of the Moon around the Earth called the revolution of the Moon. The time required for one revolution Month is a month (29½ days). When evolved, vast parts of the Moon are exposed to the Sun changes. Therefore, the shape of the Moon as seen from Earth are also changing. Spring tide occurs when the full moon and new moon. Neap tide occurs when the Moon beak. Change the shape of the Moon called the phases of the Moon.
In one revolution, the Moon suffered eight phases. When averaged, each phase of the Moon lasts for approximately 3-4 days.
The first day, the Moon is at position 0 °. The moon that are not exposed to the sun facing Earth. As a result, the Moon is not visible from Earth. This phase is called the new moon.
The fourth day, the Moon is at position 45 °. Viewed from Earth, the Moon appears curved like a sickle. This phase is called a crescent moon.
The eighth day, the Moon is at position 90 °. The moon was semicircular. This phase is called the Moon beak.
The eleventh day, the Moon is at position 135 °. Viewed from Earth, the Moon looks like a disc. This phase is called the Moon convex.
The fourteenth day, the Moon is at position 180 °. In this position, the Moon looks like a full circle. This phase is called the full moon or a full moon.
The seventeenth day, the Moon is at position 225 °. Viewed from Earth, the Moon sighting back such discs.
Twenty-first day, the Moon is at position 270 °. Moon sighting together with the Moon at position 90 °. The moon was semicircular.
Twenty-fifth day, the Moon is at position 315 °. Moon sighting in the same position with the position of the Moon at 45 °. The moon was shaped like a crescent. Furthermore, the Moon will return to its original position, ie the Moon die. Moon died the same position with the position of the new moon.
Movement influence the Earth and Moon
1. Lunar Eclipse
In that event Gerhanan obstruction of sunlight to the moon by the earth. These events resulted in becoming dark because no sunlight reflected. Lunar eclipse occurs when the position of the Sun, Earth and Moon in a straight line. The position of the earth is between the sun and moon. There are three types of lunar eclipses. Total lunar eclipse occurs when the moon is right in the area umbra (shadow of the Earth's core). If only a part of the lunar surface that comes into the shadow of the core and the other portion is in a blur, then called a partial lunar eclipse. While gerhanan penumbral lunar month when all parts are in the penumbra of the earth. At the time gerhanan penumbral lunar, moon still visible although not too bright. The length of a lunar eclipse can reach 6 months. However, for a total eclipse only 1 hour 40 minutes.
2. Solar Eclipse
Solar eclipse event is the closing of the sun by the moon which lead to obstruction of sunlight to reach the Earth. A solar eclipse occurs when the sun, earth and moon lie on a straight line. By the time the sun moon gerhanan situated between the sun and earth. Solar eclipse can not last more than 7 minutes and 40 seconds. When a solar eclipse, people banned from looking at the sun with the naked eye as this can permanently damage the eyes and cause blindness. You need to know, there are three kinds of solar eclipse is a total solar eclipse, partial solar eclipse, and the solar eclipse ring.
Total Solar Eclipse
The total solar eclipse or eclipse also called matahri perfect. occurs when the Earth's surface is covered by the shadow umbra month. This eclipse occurs only in the affected area umbra (shadow core) months.
Solar Eclipse Part
Partial solar eclipse occurs when the Earth's surface is covered penumbra month. So, the sun is not perfectly covered by the moon. At matahri partial eclipse, there are still parts of the sun's visible light. The time the partial solar eclipse over the course of time longer than the total eclipse matahri. This is because the moon wider penumbra of umbra month.
The eclipse of the sun Ring
Ring solar eclipse occurs when the moon is at its farthest from the Earth. At this position the cone length is not enough to cover the earth's umbra but umbra month extension that covers the earth. Area on the earth's surface which is located in the extension of the ring eclipse umbra months experience. In areas experiencing this eclipse, the sun glow that looks like a ring. While in the middle blurred.
The dating system
Calendar is a system to take into account the time. Time is divided into days, weeks, months, and years. There are two calendar systems, namely AD and AH
1. Calendar AD
BC calendar is also called a solar calendar, or the solar calendar. BC calendar is based on the revolution of the earth around the sun. Earth moves around the sun according to evolutionary trajectory. Once round the earth takes 365 ¼ days (1 year = 365 or 366 days).
In AD calendar, the year is divided into 12 months. Ie January, February, March, April, May, June, July, August, September, October, November, and December. The number of days each month are not the same. Determination of BC initially conducted by Julius Caesar of the Roman Empire.
Leap year is a year in which the number of the next 366 days. In February the number of the next 29 days. But in a leap year the number of days in February there were 29 days. In the leap year, year number is divisible by 4. Leap year only 1 time in 4 years. The way to determine a leap year can be done by dividing the year. The number of years divisible by 4. Example: 1980 is a leap year since 1980 is divisible by 4 (1980: 4 = 495). While 1981 is not a leap year. Because 1981 is not divisible by 4 (1981: 4 = 495 trace 1).
2. Hijri Calendar
Hijra calendar calculation based on rotation of moon around the earth. Hijra calendar is also called lunar calendar. The time it takes months to evolve a single round for 29 ½ days. One year in the Hijra calendar is divided into 12 months. Namely Muharram, Safar, Rabi early, late Rabi, Jumadil beginning, Jumadil end, Rajab, Sha'ban, Ramadan, Shawwal, Zulkaidah and Zulhijjah. Hijra calendar there is also a leap year, so-called leap years in a year when there were 355 days. One day was added in Zulhijjah, resulting in a leap year Hijri calendar in the next 30 days Zulhijjah number.