Chahal's Gyan Ki Baat
LONGITUDE
WHAT IS LONGITUDE?
- It is an angular distance, measured in degrees along the equator east or west of the Prime Meridian.
- It is a series of semi-circles that run from pole to pole passing through the equator.
- They all are equal in length.
WHAT IS PRIME MERIDIAN?
- The Prime Meridian passes through Greenwich dividing Earth in Eastern and Western hemisphere.
- All other meridians radiate Eastwards and Westwards up to 180°, from the Prime Meridian (0°).
WHAT IS THE RELATION BETWEEN LONGITUDE AND TIME?
- The earth’s rotation makes the sun rises in the east and sets in the west.
- In every 15° eastwards, local time is advanced by 1 hour.
- The places east of Greenwich see the sun earlier and gain time, whereas places west of Greenwich see the sun later and lose time.
WHAT IS THE RELATION BETWEEN LONGITUDE AND TIME?
- To find local time, just add or subtract the difference in the number of hours from the given longitude.
WHAT ARE STANDARD TIME ZONES?
- The local time of places on different meridians are bound to differ.
- To avoid these difficulties, a system of standard time is observed.
- Larger countries such as U.S.A and China have multiple time zones.
- The local time in India at the longitude of 82½° E (82° 30’E) is taken as the standard time for the whole country. It is known as the Indian Standard Time.
WHAT IS THE INTERNATIONAL DATE LINE?
- The International Date Line (IDL) is an imaginary line runs from North to South Pole.
- It is a zig -zag line that roughly follows the Prime Meridian and passes through the Pacific Ocean.
- It is this Line, where the date changes by exactly one day when it is crossed. Means, from east to west loses a day and from west to east gains a day.