Feature

Revisiting Columbus At 500... What If?

Bill Gardner

On the occasion of the Columbus Quincentennial, it is interesting to speculate on how simple optical observations, or the lack thereof, may have had a major impact on the course of world history. Standing on a pier overlooking Mobile Bay one night, we noticed a phenomenon illustrated in Figure 1. As the head of the observer descends, it reaches a height x above the water at which a string of causeway lights across the bay suddenly disappear. These lights, whose height above the water is y, drop below the horizon due to the earth's radius of curvature, R.