What is the significance of the "Prime Meridian"?

The Prime Meridian holds paramount significance as the reference line for longitude, defined at 0 degrees. This is crucial for navigation and mapping, as it serves as the starting point from which all other longitudes are measured, ranging from 0 to 180 degrees east and west. Its establishment at Greenwich, London, has standardized global navigation, allowing for consistent communication and navigation across different regions of the world. By providing a uniform reference for time zones and geographic coordinates, it enables accurate positioning and is essential for various applications in fields such as geodesy, aviation, and maritime travel.

While the other options touch on important concepts like Earth's orbit, rotational speed, and navigation history, they do not encapsulate the primary role of the Prime Meridian as a crucial reference for determining longitude in a global coordinate system.