Globe: Latitude and Longitudes

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 The Shape of the Earth

Earlier times, people considered the world as a flat disc. It extends indefinitely in all the four directions. 



By the time of the ancient Greeks (BC 1200-900), many people believed that the Earth was spherical.

Ancient Greek philosophers, Aristotle, argued that the Earth was a sphere based on his observations of the stars. 

A Greek mathematician named Eratosthenes calculated the circumference of the Earth. He is credited as “the Greek who proved the earth was round”.

Ferdinand Magellan's crew started their sail from Europe and returned back to the same spot by circumnavigating the earth. 


Isaac Newton first proposed that Earth was not perfectly round. Instead, he suggested it was an oblate spheroid—a sphere that is flattened at its poles and bulged in the middle. 

Tools to study the Earth

There are two major tools to study the earth. 

  1. Map: It captures geographic information in a flat, two dimensional format.
  2. Globe: It accurately represents the shape of the Earth. It is in three dimensional format. It is a small model of the earth which shows as different features on a smaller scale. 





Features of a Globe
  1. Globe shows the exact location. 
  2. It shows the shapes of different features of the earth.
  3. It gives us an idea about the size of land masses and water bodies. 
  4. It also gives us information about: 

  • Continents: Large landmasses, such as Africa, Asia, Europe, North America, South America, Australia, and Antarctica, are depicted on the globe.
  • Oceans: Large bodies of water, including the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean, are represented.
  • Countries: Political boundaries are often indicated on globes to show the borders between different countries and territories.
  • Capitals: Capital cities of countries are often labelled on the globe.


    • Parallel of Latitude
    The imaginary line running on the globe divides it into equal parts. This line is known as the Equator.
    All parallel circles from the Equator up to the poles are called parallels of latitude. Latitude is measured in degrees.
    As we move away from the Equator, the size of the parallels of latitude decreases.

    The four important parallels of latitude are :
    Tropic of Cancer (23 1/2° N)
    Tropic of Capricorn (23 1/2° S)
    Arctic of Circle (66 1/2° N)
    Antarctic Circle (66 1/2° S)

    Tropic of Cancer and Tropic of Capricorn

    The Tropic of Cancer was named because during the June solstice the powerhouse of the solar system i.e sun was present in the Cancer constellation. On the other hand, the Tropic of Capricorn was named because the sun was positioned in the constellation Capricorn.




  • Extra


      • Heat Zones of the Earth

      Torrid Zone: 

      This zone lies near the equator and extends approximately 23.5 degrees north (Tropic of Cancer) and south (Tropic of Capricon) of the equator. It experiences extreme hot temperatures throughout the year, with little seasonal variation. It is because the sun rays falls vertically on this region. So the heat received is maximum at these latitudes.

       There are many countries in Torrid Zones such as Indonesia, Malaysia, Thailand, Vietnam, Taiwan, Burma, Sri Lanka, India, Bangladesh, Ghana, Madagascar, Chile, Brazil, Argentina, and Mexico

      Note: India lies between the 8⁰4' N and 37⁰6' N latitudes and The longitudinal extent of India is 68°7'E to 97°25'E.

      Temperate Zone: 

      -The temperate zone lies between:

      a) the Tropic of Cancer and Arctic Circle (North Temperate Zone)

      b)the Tropic of Capricorn and Antarctic Circle (South Temperate Zone) 

      -It experiences four distinct seasons—spring, summer, autumn, and winter—with moderate temperatures. 

      -The temperate zone are not very hot because sun rays falling in these zones are slanted and cause less heat than in the torrid zone.

      Countries include Countries of Europe, North Mexico, Northern India, Pakistan, Saudi Arabia, South Africa, New Zealand, Bangladesh, Western Australia, Iran, Turkey, Iraq, Bahrain, Afghanistan etc. 

      Frigid Zone:

       Frigid means cold.

      - Beyond the Arctic Circle and Antarctic Circle temperatures are very low and the climate is very cold.
      - This is due to the extreme slanting of the Sun's rays.
      - The North Frigid Zone lies between the Arctic Circle (6612∘N) and the North Pole in the Northern hemisphere.
      - The South Frigid Zone lies between Antarctic Circle (6612∘S) and the South Pole in the Southern hemisphere.

      Countries of Frigid Zone are Denmark, Alaska, Norway, Finland, Sweden, Russia, Canada, 
      Antarctica etc. 

      Heat

      Zones of the earth

      solistice

      What are Longitudes?

      Meridians of longitude

      The lines of reference or imaginary semi-circular lines running from the North Pole to the South Pole are known as meridians of longitude.

      The meridian which passes through Greenwich, where the British Royal Observatory is located. This meridian is regarded as the Prime Meridian.

      The value of this meridians is 0° longitude and from it we count 180° eastward as well as 180° westward.

      The Prime Meridian and 180° meridian divides the earth into two equal halves which is known as the Eastern Hemisphere and the Western Hemisphere.





      Meridians of longitude are drawn from the North Pole to the South Pole and are at right angles to the Equator. The distances between meridians of longitude are measured in degrees of longitude. Each degree is further divided into minutes and minutes into seconds.


      Prime Meridian is an imaginary line on Earth that passes north to south through the Greenwich Observatory in London, England. The prime meridian divides Earth into the Eastern Hemisphere and the Western Hemisphere. The prime meridian is at 0° (0 degrees) longitude. The longitude of a place is followed by the letter E for the east and W for the west.


      Longitude and Time

      The best means of measuring time is by the movement of the Earth, the moon and the planets. 

      When the Prime Meridian of Greenwich has the sun at the highest point in the sky, all the places along this meridian will have mid-day or noon. 

      As the earth rotates from west to east, those places east of Greenwich will be ahead of Greenwich time, and those to the west will be behind it.


      The rate of difference can be calculated as follows. 

      The earth rotates 360° in about 24 hours, which means 15° an hour or 1° in four minutes. Thus, when it is 12 noon at Greenwich, the time at 15° east of Greenwich will be 15 × 4 = 60 minutes, i.e., 1 hour ahead of Greenwich time, which means 1 p.m. 

      But at 15° west of Greenwich, the time will be behind Greenwich time by one hour, i.e., it will be 11.00 a.m. Similarly, at 180°, it will be midnight when it is 12 noon at Greenwich.

      Indian Standard Time


      • From South to North. India extends between 8°4′ N and 37°6′ N latitudes.

      • From West to East, India extends between 68°7′ E and 97°25′ E longitudes.

      • The local time various places are different, so it is necessary to adopt the local time of some central meridian of a country as the Standard Time.
      • 8212°E is treated as the Standard Meridian of India. The local time at this meridian is known as the Indian Standard Time (IST).
      • India located East of Greenwich at 82° 30’E, is 5 hours and 30 minutes ahead of GMT.
      • Some countries have a great longitudinal extent and so they have adopted more than one standard time.
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