Straddling Two Hemispheres

So this past weekend I made a trip to the Prime Meridian at the Greenwich Prime Observatory in southeast London.The Prime Meridian is the location where the longitude is defined as 0° that divides the Earth into the Eastern and Western Hemispheres. There has been much dispute as to where the meridian would be because the longitude lines are rather arbitrary, according to Wiki since I'm clearly not a geography buff! The Prime Meridian was established in 1851 by Sir George Airy. During this time each major country had established its own 0° longitude, but it was not until the International Meridian Conference was Greenwich, London selected as the official meridian for its popularity.