Our Earth is not a sphere it is slightly flattened at poles.
A globe gives an idea about its look.
Without latitudes and longitudes it’s difficult to tell location on a globe.
Axis of Earth
Two points on the globe through which the needle passes are two poles – North Pole and South Pole.
The globe can be moved around this needle from west to east just as the earth moves.
Equator and Latitudes
All parallels north of the equator are called ‘north latitudes.’ Similarly all parallels south of the equator are called ‘south latitudes.’
The value of each latitude is, therefore, followed by either the word north or south. Generally, this is indicated by the letter ‘N’ or ‘S’.
Important Parallels of Lattitudes
Besides the equator (0°), the North Pole (90°N) and the South Pole (90° S), there are four important parallels of latitudes.
Arctic Circle at 66½° N
Tropic of Cancer (23½° N)
Tropic of Capricorn (23½° S)
Antarctic Circle at 66½° S
Heat Zone of the Earth
Torrid Zone (Maximum Heat Zone)
Temperate Zone (Moderate Heat Zone)
Frigid Zone (Very Cold Zone)
What are Longitudes?
Longitude, is a geographic coordinate that specifies the east–west position of a point on the Earth’s surface, or the surface of a celestial body.
It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda.
They are semicircles and the distance between them decreases steadily polewards until it becomes zero at the poles, where all the meridians meet.
What is Prime Meridian?
A prime meridian is the meridian in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian form a great circle.
In 1884, the International Meridian Conference established an internationally recognised single meridian.
It is also known as Greenwich Meridian because it passes through the place called Greenwich (where the British Royal Observatory is located) in London.
Longitude and Time
As the earth rotates from west to east hence those places which are east of Greenwich will be ahead of Greenwich time and those to the west will be behind it.
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.
Longitude and Time
Why Do We have Standard Time?
For a country like India which is widely spread from 68°E to 97°E it is very necessary to have a standard time.
82½° E (82° 30’E) is treated as the standard meridian. The local time at this meridian is taken as the standard time for the whole country. It 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. So it will be 7:30 p.m. in India when it is 2:00 p.m. noon in London.