THE EARTH

The Earth is the third planet from the Sun and comes between the planet Venus and the planet Mars.
The Earth takes 365¼ days to complete its orbit round the Sun. The Earth’s year is therefore 365 days long but
the ¼ days are added up and every fourth year has one extra day, on the 29th of February. This fourth year is
called a Leap Year (366 days) and is always a year which can be divided exactly by 4 – 2000, 2004, 2008, 2012,
2016. As the Earth orbits round the Sun it turns on its axis, rotating right round in 24 hours.

AXIS OF ROTATION is an imaginary line passing from North Pole and South Pole of the earth and it is
around this axis that the earth rotates from west to east.

• The axis is making 66 ½ degree with the orbital plane of the earth (plane formed by the orbit of the earth
  around the sun) and 23 ½ degrees from the vertical axis.

LATITUDES/PARALLELS:
Equator: It is an imaginary line running on the globe and dividing the globe in two parts-the northern part called
as the NORTHERN HEMISPHERE and the southern part called SOUTHERN HEMISPHERE (both are equal halves)

Equator passes through following Countries:
1) Ecuador
2) Colombia
3) Brazil
4) Gabon
5) Congo
6) Democratic Republic of Congo
7) Uganda
8) Kenya
9) Somalia

10)Indonesia

• All parallel circles from equator up to the poles is called PARALLELS or LATITUDES and are measured in degrees.
• All the parallels north of equator are called ‘north latitudes’ and south of equator are called ‘south latitudes’.
• The equator is zero degrees, NORTH POLE is 90 degree north(N) latitude and SOUTH POLE is 90 degree south(S) latitude.
• Total number of latitudes on the Earth is 181

OTHER IMPORTANT LATITUDES:
1. Tropic Of Cancer (23 ½ degree N)
2. Tropic Of Capricorn (23 ½ degree S)
3. Arctic Circle (66 ½ degree N)
4. Antarctic Circle (66 ½ degree S)

LONGITUDES:
The vertical longitude lines are also known as Meridians. They converge at the poles and are widest at the equator.
ZERO DEGREES LONGITUDE is located at Greenwich, England (0°) and called GREENWICH MERIDIAN or PRIME MERIDIAN.

• The degrees continue 180° east and 180° west where they meet and form the International Date Line in the Pacific Ocean. Greenwich, the site of the British Royal Greenwich Observatory, was established as the site of the prime meridian by an international conference in 1884.
• The Total Number Of Longitudes Is 360.
• The time in the longitudes east of GMT is ahead of GMT time, and in the western hemisphere, time is behind GMT time.
• The standard time for India (IST-INDIAN STANDARD TIME) is ahead of GMT time by 5 ½ hours and IST is at 82 ½ degrees E longitude.
• Countries having greater longitudinal extent have been divided into more than one standard time zone example Russia which has eleven time zones.

Composition of Whole Earth
1. Iron – 35% 6. Sulpher – 13%
2. Oxygen – 30% 7. Calcium – 1.1%
3. Silicon – 15% 8. Aluminium – 1.4%
4. Magnesium – 13% 9. Others – 0.5%
5. Nickel – 2.4%

ROTATION OF THE EARTH:

The movement of earth around its axis from west to east is called the rotation of the earth. The Exact period of rotation of earth is 23 hrs. 56 min and 4 seconds

EFFECTS OF ROTATION:

• The primary effect of Earth’s rotation is the phenomenon of day and night.
• An additional effect is that of spin or rotation placed on weather systems by what is called Coriolis Effect.
• In the Northern Hemisphere, low pressure systems rotate counterclockwise, and high pressure systems rotate clockwise. In the Southern Hemisphere, it is just the opposite.
• The rotation of the Earth also contributes to the shift of the shape of earth. The Earth is not a perfect sphere, but is flattened at the poles and has a bulge around the equator. Earth’s shape has actually been modified by its rotation, and we describe its shape as that of an oblate spheroid.