📝 Chapter Notes & Revision

Globe : Latitudes and Longitudes

🏫 MP BoardClass 6Social Science

📐 Formula & Cheat Sheet (English)

Class 6 Social Science Quick Revision Notes

Chapter: Globe: Latitudes and Longitudes (Geography)

### 1. Important Definitions (मुख्य परिभाषाएँ)

  • Globe (ग्लोब): A true miniature form (model) of the Earth. It shows countries, continents, and oceans in their correct sizes and proportions.
  • Axis (अक्ष): An imaginary line passing through the center of the Earth around which it rotates. The Earth is tilted on its axis at an angle of 23½°.
  • Equator (विषुवत वृत्त / भूमध्य रेखा): An imaginary circular line running on the Earth dividing it into two equal halves. It represents the 0° latitude.
  • Hemispheres (गोलार्ध): The two halves of the Earth.
    • Northern Hemisphere (उत्तरी गोलार्ध): The half north of the Equator.
    • Southern Hemisphere (दक्षिणी गोलार्ध): The half south of the Equator.
  • Latitudes (अक्षांश): The parallel circles from the equator up to the poles. They are measured in degrees.
  • Longitudes (देशांतर): The lines of reference running from the North Pole to the South Pole.
  • Prime Meridian (प्रमुख याम्योत्तर): The longitude passing through Greenwich, London, marked at 0°.
  • Local Time (स्थानीय समय): Time calculated by the shadow cast by the sun, which is highest at noon everywhere along the same longitude.

### 2. Key Concepts: Latitudes (अक्षांश रेखाएँ)

  • Total Number: There are 180 latitudes in total (90 in the Northern Hemisphere and 90 in the Southern Hemisphere, excluding the Equator itself).
  • Important Latitudes:
    1. Equator (विषुवत वृत्त): 0°
    2. Tropic of Cancer (कर्क रेखा): 23½° N (Northern Hemisphere)
    3. Tropic of Capricorn (मकर रेखा): 23½° S (Southern Hemisphere)
    4. Arctic Circle (उत्तर वृत्त): 66½° N
    5. Antarctic Circle (दक्षिण वृत्त): 66½° S

### 3. Heat Zones of the Earth (पृथ्वी के ताप कटिबंध)

Based on the sun's rays, the Earth is divided into three major heat zones:

  1. Torrid Zone (उष्ण कटिबंध):
    • Location: Between the Tropic of Cancer and the Tropic of Capricorn.
    • Feature: Receives the maximum heat as the mid-day sun is exactly overhead at least once a year.
  2. Temperate Zones (शीतोष्ण कटिबंध):
    • Location: Between Tropic of Cancer and Arctic Circle (North) and Tropic of Capricorn and Antarctic Circle (South).
    • Feature: Moderate temperatures; sun's rays are never directly overhead.
  3. Frigid Zones (शीत कटिबंध):
    • Location: Between Arctic Circle and North Pole, and Antarctic Circle and South Pole.
    • Feature: Very cold because the sun does not rise much above the horizon.

### 4. Key Concepts: Longitudes (देशांतर रेखाएँ)

  • Total Number: 360 meridians of longitude.
  • Prime Meridian (प्रमुख याम्योत्तर): Passes through Greenwich (Royal Observatory near London). It is 0° longitude.
  • Eastern and Western Hemispheres: Longitudes to the east of Prime Meridian up to 180° are called East ($E$), and to the west are called West ($W$).
  • Grid: The network of latitudes and longitudes on a globe is called a Grid. It helps in locating any place on Earth accurately.

### 5. Time and Longitude (समय और देशांतर)

  • Earth's Rotation: The Earth rotates from West to East.
  • Time Calculation Rule:
    • The Earth rotates 360° in about 24 hours.
    • This means 15° in 1 hour, or 1° in 4 minutes.
    • Places east of Greenwich are ahead of Greenwich time (+).
    • Places west of Greenwich are behind Greenwich time (-).
  • Indian Standard Time (IST):
    • The longitude of 82½° E is taken as the Standard Meridian for India.
    • IST is 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT).