Globe : Latitudes and Longitudes

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).