As soon as trade intercourse began, many other facts helped the growth of this belief. When ships appeared in the Mediterranean, maritime people became accustomed to the sight of the mast sinking last below the horizon, or the mountain rising first as land was sighted. Little later than 2000 B.C. Semitic traders were pushing north beyond the Mediterranean towards the Tin Isles, bringing back tales of the long summer days and the long winter nights of the northern regions. They told, too, how the aspect of the night sky changed. Stars low on the northern horizon became higher in the heavens as ships sailed into the northern seas. A fact most fatal to a flat earth view was that southern constellations disappeared entirely from view. To be sure, the belief that the earth is truly spherical (or nearly so) could only be settled by showing that a degree of latitude is the same distance if measured anywhere along any meridian of longitude, and a degree of longitude in the same latitude is always of the same length. We shall come to that later. Here it suffices to remark that the belief in the sphericity of the earth is of very great antiquity, and that there were a number of good reasons to support it.
The sun is over the equator and the time of the year is supposed to be the autumn equinox. At latitude 30° star A will be visible throughout the night in autumn and invisible at midnight in spring. At latitude 60° it will be seen crossing the meridian above the pole just south of the zenith at midnight in autumn, and will be visible throughout the spring night below the pole, making its lower culmination at midnight on the spring equinox.