What is the significance of 0 degrees longitude?

The significance of 0 degrees longitude lies in its designation as the prime meridian. This line of longitude is established at the Royal Observatory in Greenwich, England, and serves as the starting point for measuring degrees of longitude both east and west around the globe.

The prime meridian plays a critical role in navigation and mapping; it helps in the establishment of time zones by determining the standard time for mean solar time at Greenwich. Thus, all other longitudes are measured relative to this line, which is crucial for global positioning systems and various geographic calculations.

While the other options mention important concepts related to Earth's geography and time, they do not accurately capture the specific importance of 0 degrees longitude itself. For example, the equator corresponds to 0 degrees latitude, which is entirely unrelated to the context of longitude, and does not divide the Earth into eastern and western hemispheres — that function belongs primarily to the prime meridian.