Page 118 - SST Class 06

The earth’s diameter at the Equator is about Measurements
12,756 kilometers (7,926 miles). At the poles, the Although, the earth is neither a perfect circle nor
diameter is about 12,714 kilometers (7,900 a sphere, but for the purpose of calculation all
miles). The earth’s equatorial bulge is about 43 measurements are done as though it is a circle.
kilometers (27 miles). The circle measures 360° in circumference. If we

go from the equator to the North Pole or the
DO YOU KNOW?
South Pole, we would go through a quarter (¼)
Now, inflatable globes packed in small cardboard of a whole circle or 90°. Thus, from the equator
boxes are available. It is to inflate the plastic globe to the pole we mark 90 divisions each forming
like a balloon and mount it on the stand. It can be
one degree. The direction north and south of the
dismantled easily and packed in the box. It is easy to
Equator is indicated by suffixing letter N and S,
carry the box and store in a small space. Not only the
as the case may be. For determining exact
celestial globes, showing stars, constellations,
location of a place north or south of the equator,
galaxies etc., but Lunar globes are also available.
degrees are further subdivided into minutes and
seconds.
The North Pole and the South Pole are the points
where the (imaginary) axis of the earth, cuts the Each degree (°) is divided into 60 minutes written
earth’s surface. as (') and each minute is further sub-divided into
60 seconds written as ('').
The equator at the end has North Pole and
South Pole each are of 90°. LATITUDES

Problem of Location on the Earth Latitude is a measurement on a globe or map of
location north or south of the Equator.
It is usually easy to fix one’s position on land.
Technically, there are different kinds of lati-
Telephone messages such as:
tude—geocentric, astronomical and geographic
“Shall we meet outside the library?” or I have
(or geodetic)—but there are only minor differ-
run out of petrol on NH or just one km, away ences between them. In most common refer-
from Panipat towards Karnal. These references
ences, geocentric latitude is implied. Given in
are very clear to arrive at the designated place.

The nearly spherical shape of the earth, however, North Pole 90° N
presents some difficulties since it has neither a
Northern
beginning, nor an end. Besides, there is no Hemisphere
natural point or line of reference from which to
measure the relative position of other points.
The fact of rotation, however, establishes two
Equator
fixed points, the two geographical poles of the
earth. These poles serve as the needed points of
reference.
To divide the earth into the Northern
Southern
Hemisphere and the Southern Hemisphere, the Hemisphere
Equator is drawn as a circle running around the
Earth exactly half way between the poles. South Pole 90° S
Latitudes

Social Science-6 118