We occasionally read about people who have "sailed around the world." How is success defined?
—J.B., Grand Rapids, Mich. Most aficionados agree that to accomplish a true circumnavigation of the globe, the sailor must (1) head in one general direction and finish at the same place he or she started and (2) reach two diametrically opposite points on the planet (places that would be connected by a straight line running through the center of the Earth) during the journey. While doing this, the sailor would surely cross the equator and travel through all the longitudinal lines around the globe. Send questions to