The Prime Meridian

The Prime Meridian is an imaginary line that runs from the North Pole to the South Pole. It divides the Earth into the Eastern Hemisphere and the Western Hemisphere. The Prime Meridian passes through Greenwich, England. It is the starting point for measuring longitude.

Why Greenwich

In 1884, leaders from many countries met and agreed to use Greenwich, England, as the starting line. The Royal Observatory there had been used for measuring time and navigation for many years. The Prime Meridian is at zero degrees longitude.

What the Prime Meridian Does

The Prime Meridian helps us measure how far east or west a place is. All other longitude lines are measured from it. It also helps set time zones around the world. Greenwich Mean Time is based on the time at the Prime Meridian.

Fun Facts

• You can visit a line on the ground at the Royal Observatory in Greenwich that marks the Prime Meridian.
• The Prime Meridian passes through eight countries.
• The line on the opposite side of the Earth from the Prime Meridian is called the International Date Line.

Did You Know?

When you cross the International Date Line in the Pacific Ocean, the date changes by one whole day!