The Greenwich Time Ball is located at the prime meridian.
The prime meridian is a reference line through Greenwich, England that measures longitude east and west.
An example of prime meridian is zero degrees longitude.
the meridian from which longitude is measured both east and west; 0° longitude: it passes through Greenwich, England
- A meridian used as a reference line from which longitude east and west is measured.
- Prime Meridian The meridian passing through Greenwich, England, designated as the zero meridian (0°) by an international conference in 1884.