Final answer:
This question discusses the navigational principles on a spherical Earth that explain why ships disappear from the bottom first as they sail away and why lookouts could see farther from the masthead than from the deck. These principles were well understood by mariners such as Columbus, and they were critical for their navigation strategies.
Step-by-step explanation:
The question involves understanding navigational concepts, specifically in relation to the curvature of the Earth and its effects on visibility and navigation at sea. This can be explained by simple geography and the principles of spherical Earth. When a ship sails away from you on a spherical Earth, the ship disappears from the bottom up due to the curvature. The higher the observation point, such as the masthead of a ship, the further one can see because you are looking over a greater portion of the Earth's surface. If the Earth were flat, there wouldn't be significant advantages to posting lookouts on the mast since the view would not be obstructed by curvature, and so the distance seen would be about the same from the deck or the mast.
For mariners like Columbus, navigational techniques and an understanding that the Earth was not flat were essential to successfully conduct long voyages. The nautical arguments for a spherical Earth were well known to them and played a crucial role in their navigation strategies.