Thales is also said to have discovered a method of measuring the dis- tance to a ship at sea. There are several theories that conjecture his explanation. The first is to use sightings on short and to construct a congruent triangle on shore and measure the unknown distance. This explanation would have little utility, because the time of measurement of a distant ship would be so long as not to be of use.Using similarity, a bit of geometry known at the time and in partic- ular to Thales if the pyramid story is anywhre near accurate, an alternate explanation uses two shore observation points, where the angles to the ship are measured. This information is given to the observatory where the actual ship-to-shore distance is determined by creating a triangle (∆CDE) similar to triangle ∆ABS.