Introduction
Longitude, time calculation based on meridian lines, and Nepal's standard time are fundamental concepts in physical geography frequently asked in Loksewa competitive exams.
Main Content
Key geographical provisions and details regarding Longitude include:
- Definition: Longitude is the angular distance east or west from the Prime Meridian measured from the center of the Earth.
- Lines of Longitude: Semi-circular lines drawn north to south connecting the North Pole and South Pole.
- Key Characteristics:
- All longitude lines converge at the poles (distance is 0 km at poles).
- Maximum distance between two longitude lines is at the equator (approx. 111.32 km).
- All longitude lines are equal in length and intersect latitude lines at 90 degrees (right angle).
- Total number of lines: 360 (180° East + 180° West).
- Major Longitude Lines:
- Prime Meridian (0°): Passes through Greenwich, UK; divides Earth into Eastern and Western Hemispheres; base for GMT.
- International Date Line (180°): Imaginary line near 180°; crossing from west to east gains a day, east to west loses a day.
- Longitude and Time:
- Earth rotates 360° in 24 hours.
- 15° longitude = 1 hour difference.
- 1° longitude = 4 minutes difference.
- Time is ahead towards the east and behind towards the west of the Prime Meridian.
- Nepal's Longitudinal Position:
- Extends from 80°4' E to 88°12' E longitude (entirely in the Eastern Hemisphere).
- Westernmost point: Dodhara of Kanchanpur (80°4' E).
- Easternmost point: Lelep of Taplejung (88°12' E).
- Nepal Standard Time (NST):
- Determined based on the 86°15' E longitude line passing through Mt. Gaurishankar (7,134 meters) in the Rolwaling range of Dolakha district.
- NST is GMT + 5:45 (5 hours 45 minutes ahead of GMT).
- Officially declared and implemented on Baishakh 1, 2042 B.S. (prior to this, Indian Standard Time was used).
- NST is 15 minutes ahead of Indian Standard Time (IST) and 2 hours 15 minutes behind China Standard Time (CST).
Key Takeaways
- Total number of longitude lines is 360, and they converge at the North and South Poles.
- 1 degree of longitude corresponds to a time difference of 4 minutes.
- Nepal's standard time (NST) is based on 86°15' E longitude cutting through Mt. Gaurishankar and is GMT + 5:45.
- Nepal Standard Time was officially implemented on Baishakh 1, 2042 B.S.
What to Avoid
- Believing longitude lines are parallel to each other like latitude lines (they converge at poles).
- Stating Nepal's standard time is GMT + 5:30 (that is Indian Standard Time, NST is GMT + 5:45).
- Misidentifying the mountain defining NST as Mount Everest instead of Mount Gaurishankar (7,134 m).
FAQ
Q1: How much time difference does 1 degree of longitude represent? 1 degree of longitude represents a time difference of 4 minutes (15 degrees equals 1 hour).
Q2: On which longitude line and mountain peak is Nepal Standard Time (NST) based? Nepal Standard Time is based on the 86°15' Eastern longitude passing through Mount Gaurishankar in Dolakha district.
Q3: When was Nepal Standard Time officially implemented? Nepal Standard Time was officially implemented on Baishakh 1, 2042 B.S.
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