Globe: A Modal Of Earth

let's learn

• introduction

• globe

• parallels

• features of parallels

• meridians

• features of meridians

• grid

• movements of the earth

• solstices and equinoxes

our earth is a unique planet since it is the only planet that sustains life. it is home to millions of living organisms. several factors have made life possible on earth. we know that earth is spherical in shape. to locate a place on the earth, some points of reference are needed. let us learn about it with the help of a globe.

  globe  

a globe is a model of earth. it depicts the earth and shows the land and water bodies on a small scale. the blue-colored parts are the water bodies and the rest are landmasses. the deep blue color represents the deep waterbodies and light blue shows shallow waters. the large continuous masses of land are called continents. most continents are surrounded by water on three or on all sides.

there are seven continents in all. they are Asia, Africa, North America, South America, Antarctica, Europe, and Australia. the oceans of the world are all connected. although ocean water is saline, it supports a diverse range of life. plants and animals that live in the oceans together from the marine life.

there are five oceans on the earth-the Pacific, the Atlantic, the Indian, the Arctic, and the southern or Antarctic Ocean.

  the axis  

there is an imaginary line called the axis of the earth. it is drawn from the top of the earth to the bottom through the Centre of the earth. the axis is tilted at an angle of 23½˙ to the plane of the orbit. it is a fixed-line. the earth rotates on this line. thus, the axis has two endpoints which we call the north pole at the top and the south pole at the bottom.

on a globe, we can see lines drawn horizontally and vertically. these are the imaginary lines to locate or study a particular place on the earth.

  parallels  

the set of circular lines running east to west on the surface of a globe are called parallels or lines of latitude. the latitude runs parallel to each other and is equidistant to each other. these are measured in degrees.

the longest latitude that passes through the Centre of the earth midway between the north pole and the south pole is called the equator. it is also called 0˙latitude. it divides the earth into two halves, called the hemispheres. the part of the earth to the north of the equator is called the northern hemisphere, and the part to the south of the equator is called the southern hemisphere.

  features of parallels there are 180 parallels in a globe, 90 in the northern hemisphere and 90 in the southern hemisphere.

they are drawn at a gap of 1˙with the equator at 0˙.

the north pole is written as 90˙N (northern hemisphere) and the south pole as 90˙S (southern hemisphere).

other parallels are marked from 0˙ to 90˙ in each hemisphere.

the parallels at the north and south poles are reduced to a point,

unlike other parallels which are complete circles.

some important parallels:

tropic of cancer at 23.5˙N

tropic of Capricorn at 23.5˙S

arctic circle at 66.5˙N

The antarctic circle at 66.5˙S

  meridians  

vertical imaginary lines running from the north pole to the south pole are called the meridians or lines of longitude. there are 360 meridians and all are of the same length. 0˙ longitude (meridian) is called Greenwich or prime meridian, as it passes through the royal observatory at Greenwich near London, in the UK.

the prime meridian divides the earth into two halves, the eastern hemisphere, and the western hemisphere. the meridians are drawn at a gap of 1˙.

  features of meridians  

• the meridians are semi-circles.

• the distance between any two meridians increases towards the equator.

• this distance decreases towards the north and the south poles.

• the prime meridian is at the 0˙ longitude, the eastern hemisphere has 180 meridians and the western hemisphere has 180 meridians.

• 180˙E and 180˙W is the same line and is called the international date line

• the meridians cut the parallels at right angles (90)．

  grid  

the latitudes and longitudes intersect each other at right angles forming a network of lines or a grid. these imaginary lines are drawn so that we can locate a place easily with the help of the lines of latitude and longitude passing through it. this is the principle on which the global positioning system (GPS) and satellites work. let's take the example of Mumbai. as we know, Mumbai is at approx. so, the point where these two lines intersect is the location of Mumbai.

  movements of the earth

the earth moves from west to east. the two main movements of the earth are rotation and revolution. rotation is the movement of the earth about its axis, which is tilted at an angle of 23 ½˙ to the plane of the orbit. the rotation of the earth on its axis causes the occurrence of day and night. it takes the earth twenty-four hours to complete one rotation. the movement of the earth is from west to east; therefore, the part facing the sun has daytime while the other side experiences night.

revolution is the movement of the earth around the sun along a fixed path, called the orbit. it takes the earth about 365 days and 6 hours to complete one revolution. the 6 hours (or ¼ day) are added to February every fourth year. this year is known as the leap year. this movement causes four main seasons on the earth-summer, winter, spring, and autumn.

  solstices and equinoxes  

summer solstice

on June 20th or June 21st when the north pole is tilted toward the sun, and the sun shines directly over the tropic of cancer all places in the northern hemisphere experience summer. at this time, the southern hemisphere experiences the winter season.

winter solstice

on the 21st December or 22nd December, when the south pole is tilted towards the sun, and the sun shines directly on the tropic of Capricorn, the southern hemisphere experiences summer while the northern hemisphere experiences winter.

equinoxes

on the 20th/2nd of March, the spring equinox, and 22nd/23rd September, the Autumn equinox, the rays of the sun fall directly on the equator. at this time all places on the earth have equal days and equal nights, and it is known as the equinoxes.

(prepared by vidushi tyagi)