This is why prime meridian is also known as the Greenwich Meridian. In a geographical coordinate system, the Greenwich Meridian (or prime meridian) is the 0 degree line of longitude from which we measure 180 degree to the west and 180 degree to the east. Most coordinate systems define a zero line at the equator that runs east-west.

**The Prime Meridian: Defining the 0 Degree Longitude**

The correct answer is option 'B' - Prime Meridian. The Prime Meridian is an imaginary line that runs from the North Pole to the South Pole, passing through Greenwich, London, United Kingdom. It is considered the starting point for measuring longitude and serves as the reference point for determining time zones around the world.

**What is the Prime Meridian?**

The Prime Meridian is a line of longitude that divides the Earth into the Eastern Hemisphere and the Western Hemisphere. It is defined as 0 degrees longitude and serves as a reference point for measuring the east-west position of any location on Earth. The concept of the Prime Meridian was established in the 19th century to standardize global timekeeping and navigation.

**Why is it called the Prime Meridian?**

The term "Prime Meridian" is derived from the Latin word "primus," which means first or primary. It is called the Prime Meridian because it is the starting point, or the first meridian, from which all other longitudes are measured. By convention, the Prime Meridian is located at Greenwich, London, as it was the site of the Royal Observatory, where accurate measurements of longitude were first made.

**The Role of the Prime Meridian**

The Prime Meridian plays a crucial role in various aspects, including:

1. **Longitude Measurement:** The Prime Meridian serves as the reference point for measuring longitude. It acts as the baseline against which all other longitudes are measured. Locations to the east of the Prime Meridian have positive longitudes, while locations to the west have negative longitudes.

2. **Time Standard:** The Prime Meridian is widely used as the standard for determining time zones around the world. The concept of Coordinated Universal Time (UTC) is based on the Prime Meridian. Time zones are typically defined by the number of hours offset from UTC, with positive values to the east and negative values to the west.

3. **International Date Line:** The Prime Meridian and the 180th meridian, known as the International Date Line, together form a complete circle dividing the Earth into two halves. The International Date Line is located approximately 180 degrees away from the Prime Meridian and serves as the line where the date changes.

**Conclusion**

In conclusion, the 0 degree Meridian is also known as the Prime Meridian. It is an imaginary line of longitude that passes through Greenwich, London, and serves as the reference point for measuring longitude and determining time zones. The Prime Meridian plays a crucial role in global navigation, timekeeping, and establishing a standard for measuring the east-west position of any location on Earth.

Zero degree meridian is known as prime meridian...
It is the imaginary line passing through greenwich and other longitudes are designed on Earth on East and west of greenwich...
180 longitudes on East and 180 on Western side of the greenwich