The red line down the middle of the sign is defined to be zero degrees longitude, aka the Prime Meridian. It was chosen because the Greenwich Observatory was the clocks calibrated to by the British Navy. When an international prime meridian was set by convention, Greenwich was chosen because it was already in wide use around the world. Greenwich is also the home of GMT (Greenwich Mean Time).
Daily Travel Photo – Greenwich, England
Posted: December 16, 2009 Categories: Daily Photo