A neat tradition
The Greenwich Observatory sits on top of the hill that dominates the Greenwich Maritime area, where it can be seen clearly by passing boats, enabling them to adjust their watches as they approached the 0 point of GMT (Greenwich Meridian Time). Every day at five to twelve, the big red ball is prepared. At two minutes to twelve, it rises, and it drops at twelve exactly, enabling all onlookers to synchronize their watches. The tradition continues even in our digital era!