When at sea it is possible to see high mountains or elevated lights in the distance before lower lying ground and the masts of boats before the hull. It is also possible to see further by climbing higher in the ship, or, when on land, on high cliffs.
The sun is lower in the sky as you travel north, but stars such as Polaris, the north star, are higher in the sky. Other bright stars such as Canopus, visible in Egypt, disappear from the sky.
The earth throws a circular shadow on the moon during a lunar eclipse.
The times reported for lunar eclipses (which are seen simultaneously) are many hours later in the east (e.g. India) than in the west (e.g. Europe). Local times are confirmed later by travel using chronometers and telegraphic communication.
When you travel far south, to Ethiopia or India, the sun throws a shadow south at certain times of the year. Even further (e.g. Argentina) and the shadow is always in the south.
It is possible to circumnavigate the world; that is, to travel around the world and return to where you started.
Travelers who circumnavigate the earth observe the gain or loss of a day relative to those who did not. See also International Date Line.
An artificial satellite can circle the earth continuously and even be geostationary.
The earth appears as a disc on photographs taken from space, regardless of the vantage point.