What is the Geographic Grid?
If you look at a globe, you will notice some lines drawn on it vertically as well as horizontally. These lines are imaginary lines and are known as the geographic grid. This grid system was created in order to easily describe a location on the Earth.
The geographic grid is made up of lines of latitude, also known as parallels, and lines of longitude, also known as meridians.
What is the Prime Meridian?
All of us have read that the Equator is an imaginary line that divides the Earth into two parts – Northern and Southern Hemispheres.
Similarly, we also have another imaginary line called the Prime Meridian that divides the Earth into Eastern and Western Hemispheres. At times, it is also referred to as the Greenwich Meridian.
This imaginary line passes through three continents – Europe, Africa and Antarctica and four major countries – United Kingdom, France, Spain and Western Africa.
The Prime Meridian, as it passes through Greenwich, England, is considered 0 degrees longitude.
What is Greenwich Meridian Time?
We know that the Earth is round and that it takes 24 hours to complete one rotation around the sun. The side facing the sun for half a day / half a rotation is in daylight, while the side facing away has night. People living in different parts of the world cannot have the same time.
Countries all over the world are divided into 24 time zones, based on longitudinal lines. Greenwich Mean Time or GMT is the clock time at the Royal Observatory in Greenwich, London. GMT is now-a-days also referred to as Universal Coordinated Time, or UTC.
When the sun is at its highest point over the Prime Meridian, it is 12:00 noon at Greenwich.
What is the International Date Line?
The longitude at 180 degrees from the Greenwich Time Line is known as International Date Line. It was designated in 1884. If you travel west from the International Date Line, you add a day, and if you travel east from the International Date Line, you subtract a day.
3 Fun fact about the International Date Line
- Ferdinand Magellan(Born 1480 – Died 1521), a famous sea explorer set out sail around the Earth. His sailors kept a careful record of time and dates as they traveled. Yet, when they came back to the place from where they had started, they noticed that their calendars were off by one day. What had happened?
- Well, the day was not lost at once; it was lost little by little, as they sailed across the planet.
- The explanation is simple; if you stay at one place, a day lasts for 24 hours, but if you travel across the Earth, you may add or lose a day in your calendar, depending on the direction in which you are travelling!