Latitudes & Longitudes || Time Zones of the World
Important
Parallels of Latitudes:
❖
Tropic of Cancer (23 1⁄2° N) in the
Northern Hemisphere.
❖
Tropic of
Capricorn (23 1⁄2° S) in the Southern Hemisphere.
❖ Arctic Circle at 66 1⁄2° in the North of the Equator.
❖ Antarctic Circle at 66 1⁄2° in the South of the Equator.
❖ Equator: The Equator is an imaginary
line running on the globe that divides it into two equal parts.
❖ The northern half of the Earth is the Northern Hemisphere and the Southern half is the Southern Hemisphere.
❖Parallels of latitude are drawn at an interval of one degree. If the earth were a perfect sphere, the length of 1 ̊ of latitude would be a constant value, i.e., 111 km everywhere on the earth. But to be precise, the degree of latitude changes slightly in length from the equator to the Poles.
➢
At the Equator, there is high insolation.
➢
At the Tropics, there is moderate insolation.
➢ At the Poles, there is low insolation. [Therefore, due to different intensities of sunlight and heat, the vegetation and weather in different regions are different.]
❖ Torrid Zone: Overhead rays are concentrated in this zone and thus there is high insolation in a small area.
➢ The
mid-day sun is exactly overhead at least once a year on all latitudes in between the Tropic of Cancer and the Tropic
of Capricorn.
➢
It, therefore, receives the maximum heat.
➢ The
highest temperature on Earth is found near the Tropical areas.
❖ Temperate Zones: The mid-day sun never
shines overhead on any latitude beyond the
Tropic of Cancer and the Tropic of
Capricorn.
➢ The
angle of the sun’s rays goes on decreasing towards the poles. They, thus, have
moderate temperatures.
❖ Frigid Zones: Insolation is low and
covers a large area. In this zone heat energy is not concentrated.
➢ Areas
lying between the Arctic Circle and the
North Pole in the Northern Hemisphere and the Antarctic Circle and the South Pole in the Southern Hemisphere,
are very cold.
➢
It is because, here, the sun does not rise much
above the horizon.
➢
Coniferous
trees are found in these areas.
➢ Tundra and Taiga type of vegetation is found.
India as a Geographical Unit:
❖
The Tropic of Cancer passes through eight states in India.
❖ Gujarat
(Jasdan), Rajasthan (Kalinjarh), Madhya Pradesh (Shajapur), Chhattisgarh
(Sonhat), Jharkhand (Lohardaga), West- Bengal (Krishnanagar), Tripura (Udaipur)
and Mizoram (Champhai).
|
Countries Passing Through |
|
Countries
|
|
Equator
|
❖ |
South America: Ecuador, Colombia, Brazil |
|
|
❖ |
Africa: Sao Tome
and Principe, Gabon, Congo, Democratic Republic of Congo, Uganda, Kenya,
Somalia. |
|
|
❖ |
Asia: Maldives, Indonesia, Kiribati |
|
Prime
Meridian |
❖ |
Europe: UK, France, Spain |
|
|
❖ |
Africa: Algeria, Mali. Burkina Faso, Ghana, Togo |
|
|
❖ |
Antarctica |
|
Tropic
of Cancer |
❖ |
North America: Bahamas (Archipelago), Mexico |
|
|
❖ |
Africa: Egypt, Libya, Niger, Algeria, Mali, Western Sahara,
Mauritania |
|
|
❖ |
Asia: Taiwan, China, Myanmar, Bangladesh, India, Oman, UAE, Saudi
Arabia |
|
Tropic
of Capricon |
❖ |
South America: .Argentina, Brazil, Chile, Paraguay |
|
|
❖ |
Africa: Namibia. Botswana, South Africa. Mozambique. Madagascar |
|
|
❖ |
Australia |
Longitude:
❖ It's
the angular distance east or west of the Prime
Meridian. It is also measured in
degrees.
❖ The
longitudes vary from 0° to 180° eastward and westward of the Prime Meridian. (Also called meridian).
❖ Prime Meridian: In 1884, it was decided to choose as zero meridian the one which passes through the Royal Astronomical Observatory at Greenwich, near London as a Prime Meridian. Meridian.
❖ The
distance between longitudes decreases from the Equator towards the Poles (It is
maximum at the equator).
❖ On
the globe, longitude is shown as a series of semi-circles that run from pole to
pole passing through the equator. Such lines are also called Meridians.
❖ They
have one very important function, they determine local time in relation to G.M.T. or Greenwich Mean Time, which is
sometimes referred to as World Time.
❖ The
distance between longitudes at the equator is the same as latitude, roughly 69 miles.
❖ At
45 degrees north or south, the distance between them is about 49 miles (79 km).
❖ The
distance between longitudes reaches zero at the poles as the lines of meridian
converge at that point i.e. the degree
of longitude decreases in length from the equator to the pole.
❖
At the
Equator the distance between two longitudes is maximum and at the Poles it is
minimum.
Facts
about Line of Longitude:
❖
These are also known as meridians that run in a north-south direction.
❖
It helps in measuring
the distance east or west of the prime meridian and calculating the local time in different areas.
❖
These are farthest apart at the Equator and meet
at the poles.
❖
These lines cross the Equator at right angles.
❖
It lies in planes that pass through the Earth’s
axis.
❖
These are equal in length and halves of great
circles.
❖
The primary unit in which longitude and latitude
are given is degrees (°). There are 360° of longitude (180°
East ↔ 180° West) and 180° of
latitude (90° North ↔ 90° South). Each degree can be broken into 60 minutes
(’). Each minute can be divided into 60 seconds (”).
Standard
Time and Time Zones:
❖ If
each town were to keep the time of its own meridian, there would be much
difference in local time between one town and the other.
❖ Travelers
going from one end of the country to the other would have to keep changing
their watches if they wanted to keep their appointments. This is impractical
and very inconvenient.
❖
Most countries adopt their standard time from
the central meridian of their countries.
❖ In larger countries such as Canada, U.S.A., China, and U.S.S.R, it would be inconvenient to have single time zone. So, these countries have multiple time zones
❖
Both Canada and the U.S.A. have five time zones
—the Atlantic, Eastern, Central,
Mountain, and Pacific Time Zones.
❖ The
difference between the local time of the
Atlantic and Pacific coasts is nearly five hours. U.S.S.R had eleven time
zones before its disintegration.
International
Date Line:
❖
International Date Line is an imaginary line where the date changes by exactly one day when it is
crossed.
❖
The International Date Line in the mid-Pacific
curves from the normal 180° meridian at the Bering Strait, Fiji, Tonga, and other islands to prevent confusion
of day and date in some of the island groups that are cut through by the
meridian.
Why
International Date Line is Zig Zag?
❖
Some groups of Islands (Polynesia, Melanesia, Micronesia) fall on either side of the
dateline.
❖ If
the dateline was straight, then two regions of the same Island Country or
Island group would fall under different date zones.
❖
Thus, to
avoid any confusion of date, this line is drawn through where the sea lies
and not land. Hence, the International Date Line is drawn in a zig-zag manner..
Greenwich
Mean Time (GMT):
❖
It is the name for
the mean solar time of the longitude (0°) of the Royal Greenwich Observatory in England. The meridian at this longitude
is called the Prime Meridian or Greenwich Meridian.
❖ Rotation
of Earth of 360° in one day or 24 hours. Therefore, 15° in one hour or 1° in 4
minutes.
❖ Earth
rotates from West to East, so every 15° we go eastward, local time is advanced
by 1 hour.
❖ If
we go westward, local time is retarded by one hour.
➢
East of
Greenwich → see the sun earlier → Gain time (East-Gain-Add).
➢ West of Greenwich → see sun later →
Lose time (WestLose-Substract).
❖
India is
5 hrs 30 min ahead of GMT.
❖ From
Greenwich to 180° E → Gain 12 hours. Similarly, from
Greenwich to 180°
W → Lose 12 hours.
❖ Thus,
a difference of 24 hours between the two sides of the 180° meridian. This is the
International Date Line (IDL).
❖ Thus,
while crossing IDL: East to West →
Loses a day; West to East → gains a day ❖ IDL
passes through the middle of the Pacific Ocean.
❖
Local time varies from one longitude to another
longitude.
❖
In the world, there are 24 time zones.
❖
USSR- 11
Time zone
❖
USA-
4 Time zones (Pacific Time, Mountain Time, Central Time, Eastern Time)
Indian
Standard Time:
❖ The local time of
places which are on different meridians
is bound to differ.
❖
In India, for instance, there will be a
difference of about 1 hour and 45
minutes in the local times of Dwarka in Gujarat and Dibrugarh in Assam.
❖
In India, the longitude of 82 1⁄2°
East
(82° 30’East) is treated as the standard meridian. The local time at this
meridian is taken as the standard time for the whole country. It is known as
the Indian Standard Time (IST).
❖
States through which IST passes are Uttar Pradesh, Madhya Pradesh,
Chhattisgarh, Odisha, and Andhra Pradesh.
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