NCERT Class 6 Geography Chapter 2 Notes from chapter 2 Globe: Latitudes and Longitudes.
What is Globe?
Globe is a small spherical model of the earth. It can have various sizes and types but it has the exact shape as the Earth i.e. the Geoid shape. On the globe, countries, continents, and oceans are shown on a smaller scale. Globe is used for studying the earth. Globe shows us the shapes and locations of various important cities of the countries.
What is the Exact Shape of the Earth?
The actual shape of the earth with all the landforms and the oceans is called the Geoid shape. It is not completely sphere. It is flat at the north and south poles and bludgeoned along the equator. This ellipsoid type of shape of the earth is called Geoid shape.
What is an axis?
Earth’s axis is an imaginary line that passes through the North Pole, center & the South pole of the earth. It is around this line earth rotates from the West to the east direction or anticlockwise direction. The globe is set to rotate in the same way as the Earth is rotating about its axis.
What is Obliquity of the Earth?
Obliquity is an angle of tilt of the Earth’s axis of rotation. It is the angle between the plane of the Earth’s equator and the plane of the Earth’s elliptic orbit around the Sun.
What is the Equator?
The Equator is the imaginary line dividing the Earth into two equal halves. The northern half is called the Northern Hemisphere and the southern half is called the Southern Hemisphere.
What are Latitudes?
The Equator is a circle that passes through half of the earth. All the parallel circles from the equator to both the poles are called parallels of latitudes or latitudes.
Latitudes are used as reference lines to locate any place on the Earth or globe.
The value of each latitude is followed by N or S to indicate whether the location is in the northern hemisphere or southern hemisphere.
The latitude of any place gives us its location with respect to the equator.
What are the Features of latitudes?
Latitudes are parallel to each other and have equal distance from each other all along the latitudes.
Latitudes are full circles everywhere except at the poles. At poles, they are just points.
At the Equator, the circle is the biggest and it decreases in size as we move towards the poles.
What are the important latitudes?
North pole (90° N)
Arctic Circle (66.5° N)
Tropic of Cancer (23.5° N)
Tropic of Capricorn (23.5° S)
Antarctic Circle (66.5° S)
South Pole (90° S)
What are the different Heat Zones (Climate Zones) of the Earth?
Various areas divide into temperature or climate zones based on the average temperature and the climate conditions.
Torrid Zone (Tropical Region)
- The area between the Tropic of Cancer (23.5° N) and Tropic of Capricorn (23.5° S)
- Very hot and humid climate.
- This region receives maximum heat from the Sun because of the direct sun rays.
- The area between the Tropic of Cancer (23.5° N) and the Arctic Circle (66.5° N) in the Northern Hemisphere. (Northern temperate zone)
- The area between the Tropic of Capricorn (23.5° S) and the Antarctic Circle (66.5° S) in the Southern Hemisphere. (Southern temperate zone)
- The temperature remains moderate in these regions because of the slanted Sun rays at even at noon.
- This region lies between the Arctic Circle (66.5° N) and the North Pole (90° N). (North Frigid zone)
- This region lies between the Antarctic Circle (66.5° S) and the South Pole (90° S). (South Frigid zone)
- The temperature remains very cold in these regions as the sun rays fall at very low angles.
- 6 months of days and 6 months of the night in these regions.
Longitudes are the imaginary semi-circles between the poles from North to South throughout the globe. They are also called Meridians.
- Any two longitudes have the maximum distance between them at the Equator and the minimum distance (zero) at the poles.
- Longitudes are perpendicular to the latitudes everywhere.
- Longitude running through Royal Observatory at Greenwich in London is taken as reference 0°. This longitude is also called Greenwich meridian or Prime Meridian.
- Longitudes divide the Earth into 2 equal parts i.e. Eastern hemisphere and the Western hemisphere.
- There are a total of 360° of longitudes. 180° East and 180° West.
- 180° E and 180° W are on the same line as the Earth is round.
- Longitudes tell us whether a place is located in the eastern hemisphere or western hemisphere.
These Lines of Latitudes and Longitudes together make a grid of lines. This grid is called the global grid. This grid is used to locate any place on Earth. with the help of latitudes and longitudes as the coordinates of the place.
Let us take an example grid,
Latitudes (A, B, C, D, E,)
Longitudes(1, 2, 3, 4)
Location of the place ‘a’ is given (B, 1). Similarly, other locations can be given.
Latitudes and Longitudes of India
- India lies in the Northern-Eastern part of the world.
- Latitudes: 8°4′ N to 37°6′ N
- Longitudes: 68°7′ E to 97°25′ E
Longitude and Time
- Longitudes are the semi-circles between the poles from North to South.
- Longitudes are used to locate any place with respect to the prime meridian.
- Longitudes indicate whether any place is located in the east to the prime meridian or west.
- Longitudes also decide the Time Zones of various places depending upon their location.
Time zone is an area where uniform time is considered for all purposes. Everyone will follow the same time value.
- Earth takes 24 hours to complete one rotation (west to east) about its own axis. Hence we have the day of 24 hours.
- Reference is taken at Prime Meridian (0°)
- The angle value of the full circle of the earth from east to west is 360°. (180° East and 180° West)
So, Earth takes 24 hours to complete 360° rotation about its axis.
The World is divided into 24 slices where each slice is 1 hour or 15° apart. (360°/24 = 15°)
i.e. (60 minutes = 15°) and (30 minutes = 7.5°)
So any two places having a longitude difference of 15° will have 1 hour time difference.
Important Points related to Time Zones
- Since the earth rotates from East to West, So the eastern places will experience the sunrise first and will be ahead in time.
- To follow a standard uniform time in an area, countries decided to use various time zones.
- Although the world is divided into 24 time zones of 1 hour apart there are countries that are 30 mins or 45 mins apart. So other additional time zones are also created to accommodate these time differences.
- Time zones are off-set with respect to reference longitude (prime meridian) where Coordinated Universal time (UTC) is considered.
- UTC is also called GMT (Greenwich Mean Time)
How to decide the time zones for any area?
If any country is 15° E from the prime meridian then it will have the time zone as (UTC + 1) hour.
- Example: If there is 1 pm at 0° longitude (London) then at the place 15° E will have 2 pm as the standard time. The place at 15° E will be 1 hour ahead of the place at 0°.
Similarly, places on the west side will be behind in time depending upon the longitude difference. You can see all the time zones in your mobile or computer time settings.
Indian Standard Time (IST)
India is a big country. It lies between (8°4′ N – 37°6′ N) latitudes and (68°7′ E – 97°25′ E) longitudes.
These Longitudes (68°7′ E – 97°25′ E) decide our standard time in India.
How the IST (Indian Standard Time) is decided?
Longitude 68° E is 4 hours and 30 mins ahead of UTC.
15° is equal to 1 hour.
(68°/15° = ~4.5 hours) Longitude 97° is 6 hours and 30 mins ahead of UTC.
(97°/15° = ~6.5 hours) So there is a difference of ~30° or 2 hours between the West (Gujarat) and East (Arunachal Pradesh)parts of India. All these options are possible to opt as the time zones:
(UTC+430, UTC+500, UTC+530, UTC+600, UTC+630)
But to keep the standard time uniform, India chose the average of the longitudes (82.5° E) and it corresponds to 5 hours and 30 mins difference from the UTC.
Standard Meridian of India: 82.5° E
The time corresponding to 82.5° E is called Indian Standard Time (IST).
IST: UTC + 530
Indian Standard time is the time corresponding to the longitude 82.5° E and its value is UTC+530.
Indian time is 5 hours 30 mins ahead of London (United Kingdom).