Folklore of the Medieval period, that which followed on from a previous dark Middle age after the Roman period, associated with climate catastrophes, comets and what not to stir the souls of the medieval people included the danger of sailing off the edge of the world while, perchance, also sailing towards China. These are considered fantastic ideas and usually dismissed as nonsense.
Maybe not, for it depends much on how we understand the process of thinking which is basically the recollection of memories and the subsequent internal voicing of words into patterns that we call thoughts. Obviously one cannot recall something that has never been ever observed or experienced in the first place, and then if the observed phenomena is novel, explained in terms of the existing lexicon. So Australian aboriginals on seeing enormous, persistent electric discharges between the Earth and the morning star or heavens would memorise these observations metaphorically as a rainbow serpent, since the movement of an electric plasma discharge between two conductive bodies, as demonstrated in the laboratory Van der Waals experiment, appears like a snake or serpent. So what about the sailing off the edge of the Earth idea?
Simpler than it seems, for if we imagine a smaller Earth with no Atlantic Ocean but perhaps a small sea that people regularly sailed on to a land known as China to the west, (think pre Tertiary Americas), and that subsequently the Atlantic Ocean depression was formed catastrophically by a volume expansion of the Earth, then that crustal upheaval would suddenly create an enormous topographic low into which the earlier pre-existing epicontinental seas would empty into and any unfortunate sailor would have the impression that he was literally sailing off the edge of his known world into the Abyss of the Atlantic. The cause of this geological fantasy is more or less Velikovskian.
I should mention that the late Lyall Watson, South African biologist and author who penned the popular book “Super Nature”, among others, reported an anecdote in one of his books, quoting a secondary source, that Medieval sailors navigated using Venus, even during the middle of the day. We no longer see Venus during the day leading to the issue of why. Watson’s explanation was that humanity lost the ability to see such phenomena as a result of evolutionary changes. I would offer a different explanation, that Venus became invisible because it became less bright over time. This explanation becomes interesting in the Velikovskian sense in which Velikovsky asserted that Venus was a young planet and must thus have been extremely hot and hence bright.
So one wonders why the British Admiralty sent Cook during the 18th century on his Pacific Ocean voyages to measure the transit of Venus. A disappearing Venus ?
Fantastic? Obviously. Plausible? Yes but not if you are a devotee of creationism and/or its liberal offspring Uniformitarianism, a dogma stuck with the job of explaining how something can be evolved out of nothing; in its case the abundance of time being the mechanism to achieve the impossible.
Given the proliferation of fake news these days, and the more unsettling observation that many of the fakirs of news seem to believe their fakes, I would tend not to casually dismiss the Medieval Myths out of hand, but to see if these myths had an origin in some or other geological fact, no matter how heretical such an idea might be.
After all the famous British economist John Maynard Keynes said that when the facts change, he changes his mind; and what do the rest of us do? Keynes had a scientific mind, in that it was capable of change.
These medieval myths suggest that the Roman Termination Event might have been a bit more than a couple of unpleasant climate catastrophes. It all rests on what one prefers to believe, or not, and whether one is prepared to think out of the box as it were. This leads to the view that the causative agents were planets, Venus, Mars, etc as recorded in Roman and Greek histories, or our interpretations, which have since been replaced by metaphysical agents that seem to be feared as much as their physical antecedents. While it’s one thing being fearful of a dangerous physical prodigy, whether rampaging elephant or white pointer shark, it’s another when the fear is purely metaphysical and thus totally imagined, whether some or other deity or in the secular world, some climate catastrophe prophesied by sacred computer models.
Update: If South America is rejoined back to Africa and Europe, then one would sail west to China from the Americas. Hence the formation of the Atlantic Ocean would make the passage a wee bit longer and would explain why the Medieval peoples believed that sailing west would lead one to China. It would if the Atlantic Ocean didn’t exist in the past.