Monday 21 November 2016

World Geography_Earth Important Facts Part-II


Earth Solar System
· Earth solar system consists of :
· The Sun
· The Planets
· Dwarf Planets and countless fragments of left –overs called asteroids, meteors, comets and satellites of the planets (Called small solar system Bodies).
Solar System Some Facts
· Biggest Planet: Jupiter
· Smallest Planet: Mercury
· Nearest Planet to Sun: Mercury
· Farthest Planet from Sun: Neptune
· Nearest Planet to Earth: Venus
· Brightest Planet: Venus
· Brightest star after Sun Sirius
· Planet with maximum satellites: Jupiter
· Coldest Planet: Neptune
· Hottest Planet: Venus
· Heaviest Planet: Jupiter
· Red Planet: Mars
· Biggest Satellite: Gannymede
· Smallest Satellite: Deimos
· Blue Planet: Earth
· Morning/Evening Star: Venus
· Earth's Twin: Venus
· Green Planet: Neptune
Planet with a big red spot: Jupiter
· Lord of the Heavens: Jupiter
· Greatest Diurnal Temperature: Mercury
Earth Movement
· The Earth also called Blue Planet. It is the densest of all planets.
· Earth Circumference : 40,232 Kilometers.
· Earth Area : 510 million Square Kilometers
Average distance from sun: 149 million-Kilometers.
· Earth Perihelion : Nearest position of earth to sun. The earth reaches its perihelion on January 3 every year at a distance of about 147 million-Kilometers.
· Aphelion : Farthest position of earth from sun. The earth reaches its aphelion on July 4, when the earth is at a distance of 152 million Kilometers.
· The shape of the earth is oblate spheroid or oblate ellipsoid (i.e. almost spherical, flattened a little at the poles with a slight bulge at the centre).
Types of Earth Movements:
· 1. Rotation or daily movement.
· 2. Revolution or annual movement.
Earth Rotation
· Spins on its imaginary axis from west to east in 23 hrs, 56 min and 40.91 sec.
· Rotational velocity at equator is 1667 Kilometers/h and it decreases towards the poles, where it is zero.
Earth’s rotation results in
· i . Causation of days and nights;
· ii . A difference of one hour between two meridians which are 15° apart;
· iii. Change in the direction of wind and ocean currents;
· Rise and fall of tides everyday.
· The longest day in North Hemisphere is June 21, while shortest day is on 22 Dec (Vice-versa in S. Hemisphere).
· Days and nights are almost equal at the equator. 
Earth Revolution
· It is earth’s motion in elliptical orbit around the sun. Earth’s average orbital velocity is 29.79 Kilometers/s.
· Takes 365 days, 5 hrs, 48 min and 45.51 sec. It results in one extra day every fourth year.
· Revolution of the earth results in
i . Change of seasons
ii . Variation in the lengths of days and nights at different times of the year
iii . Shifting of wind belts
iv . Determination of latitudes.
The 4 Earth Seasons are:
Spring: On March 21, the sun is directly overhead the equator. This is the season of spring in the northern hemisphere.
· Summer: On June 21, the sun is directly overhead the Tropic of Cancer. Thus, the northern hemisphere experiences summer.
· Autumn: On September 23, the sun returns to the equator, and the northern hemisphere experiences autumn.
· Winter: On December 22, the sun is at the Tropic of Capricorn, and the northern hemisphere experiences winter.
Earth Latitude and Longitude
Earth Latitude
· Imaginary lines drawn parallel to the equator. Measured as an angle whose apex is at the centre of the earth
· The equator represents 0° latitude, while the North Pole is 90° N and the South Pole 90° S
· 23½° N represents Tropic of Cancer while 23½° S represents Tropic of Capricorn.\
· 66½° N represents Arctic Circle while 66½° S represents Antarctic Circle.
· There are total 181 latitudes including the equator. Each parallel of latitude is a circle, but they are not equal.
· The circle becomes smaller towards the poles. Equator is the ‘Greatest Circle’ that can be drawn on the earth’s surface.
· The distance between any two parallels of latitude is always equal.
Earth Longitude
· It is the angular distance measured from die centre of the earth. On the globe the lines of longitude are drawn as a series of semicircles that extend from the North Pole to the South Pole through the equator. They are also called meridians.
· The distance between any two meridians is not equal. At the equator, 1 degree = 111 km. At 30°N or S, it is 96.5 km. It goes on decreasing this way until it is zero at the poles.
· There are 360 meridians of longitude. The prime meridian is a longitude of 00, passing through the Royal Observatory at Greenwich near London.
· This meridian is taken by geographers to divide the earth into the eastern and the western hemispheres. · Each meridian of longitude is a semi-circle. 180° meridian (International Date Line) lies exactly opposite to ° meridian. Such points are called Antipodl Points.
· The earth is divided into 24 longitudinal zones, each being 15° or 1 hour apart in time (4 minutes / degree) 
Longitude and Time
· Places that are on the same meridian have the same local (sun) time. Since the earth makes one complete revolution of 360° in 24 hours, it passes through 15° in one hour or 1° in 4 minutes.
· The earth rotates from west to east, hence places east of Greenwich see the sun earlier and gain time whereas places west of Greenwich see the sun later and lose time.
· India, whose longitudinal extent is approx. 30°, has adopted only one time zone, selecting the 82.5°E for the standard time which is 5 hours and 30 minutes ahead of GMT (Greenwich Mean Time).
International Date Line
· It is the 180° meridian running over the Pacific Ocean, deviating at Aleutian Islands, Fiji, Samoa and Gilbert Islands.
· Travelers crossing the Date Line from west to east (i.e., from Japan to USA) repeat a day and travelers crossing it from east to west (i.e., from USA to Japan) lose a day.
Earth Eclipses
Earth Lunar Eclipse
· When earth comes between sun and moon. · Occurs only on a full moon day. However, it does not occur on every full moon day because the moon is so small and the plane of its orbit is tilted about 5° with respect to the plane of the earth’s orbit. It is for this reason that eclipses do not occur every month. · This light is red because the atmosphere scatters the other colors present in sunlight in greater amounts than it does red.
Earth Tides
Earth Tides
· Refer to the phenomenon of regular rise and fall of the sea water. Though both sun and moon exert gravitational force on earth, resulting in the production of tides, the moon, by nature of its closeness to the earth, has greater control over the timings of the tidal rises and falls.
· The interval between two tides is 12 hrs and 26 minutes.
Spring Tide
· When the sun, moon and the earth are in a straight line, the gravitational force is at its greatest because tide producing forces of both sun and moon complement each other and they pull together. This produces tides of unusually great range, called the spring tide.
· These occur about twice a month: at new moon when the sun and the moon are in conjugation and at full moon when they are in opposition. 
Neap Tide
· Lowest magnitude as the tide producing forces of sun and moon act opposite to each other, as they form a triangle.
· This happens during phases of first and third quarter, i.e., at half moon, the sun’s tide producing force tends to balance the tide producing force of the moon., resulting in tides of unusually small range known as neap tides.

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