Yay! I kept looking at the globe, thinking you were providing a misleading clue. The lines of latitude and longitude stood out and when I checked "longitude" in Wikipedia, I was turned off by all the math, but curious about the Prime Meridian. It's article lists a number of prime meridians all over the earth, but in 1884, George Airy's Greenwich, England location was established by international agreement. The article actually lists three different locations for the Greenwich meridian. Airy was off by 5.3 arcseconds (about 102 meters) from the modern IERS Reference Meridian established by satellite navigation systems and doppler surveying systems. Not bad.
The Prime Meridian establishes a reference for locations east and west on the earth's surface and has been essential to navigation. I prefer GPS. It seems strange that some folks in the UK live in the Western Hemisphere and some live in the Eastern Hemisphere. The Prime Meridian is also the base of reference for nautical time zones and loosely for land time zones, which, like Daylight Savings Time, are political creations. When we hear a reference to "zulu time" that's the time at the Royal Observatory in Greenwich.
Markings of the prime meridian at the Royal Observatory, Greenwich.
I have a question about Zombie's globe. What is the great circle which crosses the equator at the prime meridian?