Globe: Latitudes and Longitudes [ Summary Notes] ~ Civil Services Self Study

What is the equator?

The equator is an imaginary line running across the globe that divides the globe into two equal parts.

Northern Hemisphere:

The half of the Earth located north of the equator is called the Northern Hemisphere.

Southern Hemisphere:

The half of the Earth located to the south of the equator is called the Southern Hemisphere.

Earth-Size:

The Earth is slightly flattened at the north and south poles and bulges in the middle. Earth has two poles which are the North Pole and the South Pole.
The earth moves from west to east.

What are latitudes?

Latitudes are measured in degrees. All parallel circles from the equator to the poles are called lines of latitude.

The equator is also called zero degrees latitude.
All parallel north of the equator is called northern latitude.
All parallel south of the equator is called southern latitude.
On moving away from either side of the equator, the length of the latitudes decreases, that is, the equator is the longest and the length of the latitudes at the poles is zero.

Some other important latitudes are:

Why do poles measure by 90 degrees?

Since the distance from the equator to any pole is one-quarter of the circle around the earth; So 360/4=90 degrees.

What is the Torrid [tropical] zone of the Earth?

This area between the Tropic of Cancer(23.5 N) and the Tropic of Capricorn (23.5 S) is called the Tropical Zone.
In these regions, the meridian Sun is directly overhead at all latitudes at least once a year. Therefore, this region receives maximum heat, it is called the Earth's tropics or torrid zone of the earth.

What are the Earth's temperate zones?

In the Northern Hemisphere, the region between the Tropic of Cancer (23.5 N) and the Arctic Circle (66.5 N), and in the Southern Hemisphere between the Tropic of Capricorn (23.5 S) and the Antarctic Circle (66.5 S) is called the Temperate Zone.
The temperature in this region remains moderate. Because:

The midday sun never falls perpendicular to any latitude after the Tropic of Cancer and the Tropic of Capricorn.
The rays of the sun go slanting towards the poles.

What are the cold tropics regions?

The region between the Arctic Circle(66.5 N) and the North Pole in the Northern Hemisphere and the Antarctic Circle (66.5 S) and the South Pole in the Southern Hemisphere is called the Cold Zone.
These regions are very cold because here the sun does not rise much above the horizon. Hence horizon rays provide less heat.

What are longitudes?

Longitudes are imaginary lines running from the North Poles to the South Poles.
The distance between longitudes is measured in degrees of longitude. Each degree is further divided into minutes and minutes into seconds.
The distance between the longitudes at the poles is zero and is greatest at the equator, i.e. the distance between the longitudes decreases as you move towards the poles.
Unlike latitudes, all longitudes have the same length.
The longitude passing through Greenwich is called the Prime Meridian and has a value of zero (0) degrees. Longitudes are calculated up to 180 degrees east and 180 degrees west of the prime meridian.
The 180 degree east and 180 degree west longitude lines are the same.
The meridian 180 degrees east of the main meridian is called the Eastern Hemisphere and the meridian 180 degrees west of the main meridian is called the Western Hemisphere.

How are day and time measured?

The motion of the earth, moon, and planets is the main factor in measuring time.
Local time can be measured by the shadow cast by the Sun.
The shadow is shortest in the afternoon and greatest at sunrise and sunset.
As we know, the Sun rotates from west to east, so the time west of Greenwich will be behind and the time of the area east of Greenwich will be ahead.

Why do we follow standard time?

It is difficult to prepare a separate timetable for each longitude, so for convenience, we have standard time.
There is a standard time in India too, although there exists a time difference of 1 hour and 45 minutes between Dibrugarh and Dwarka in Assam.
In India, the longitude of 82.5 degrees east is considered as Indian Standard Time (IST).
There are 11 (Eleven) Standard Time in Russia.
Earth has been divided into 24 (twenty-four) time zones on the basis of an interval of one hour.

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