In the Biblical account of creation, G-d divided the waters. The rabbi and Biblical commentator Nachmanides wrote about this that he believes the Greek demonstration that the earth is mostly covered with water.

I've been thinking about this statement. At first blush, the portion of the earth covered with water obviously seems to be an empirical question which could not be resolved by any logical argument. But I wonder whether Nachmanides was thinking of an ancient computation about the size of the earth (based on sun angles establishing the degrees of arc between two places at a known distance), coupled with the assumption that someone sailing west from Europe would encounter no land for most of the way to Japan, as apparently anyone would have thought who was unaware of the Americas.

(He would also need some opinion about the size of the known world, but apparently this is the easy part.)

Is there any way of identifying this argument with any greater specificity? What works of Greek geography (or what would the word be?) were available to Nachmanides, and which of these dealt with the question of the amount of the earth's surface covered by water? How widely shared was this opinion?

  • $\begingroup$ Maybe useful Dirk Couprie, Heaven and Earth in Ancient Greek Cosmology From Thales to Heraclides Ponticus (Springer, 2011) $\endgroup$ Sep 14 at 6:05
  • $\begingroup$ According to Aristotle, Thale of Miletus advanced the hypothesis that the nature of all matter was a single material substance: water. Thales thought the Earth must be a flat disk which is floating in an expanse of water (an hypotheses that can be quite easy to understand for a society that flourished on the island spread into the Mediterranean Sea). $\endgroup$ Sep 14 at 6:08
  • $\begingroup$ What historical documents did Nachmindes provide or reference to back up his position? From the wiki entry it appears he studied only religious texts, which are hardly a reliable source of scientific data. $\endgroup$ Sep 14 at 11:28
  • 2
    $\begingroup$ The Greeks did not know about existence of Americas, Australia and Antarctica, but nevertheless their conclusion was right: the Earth is indeed mostly covered by water. $\endgroup$ Sep 14 at 12:25
  • $\begingroup$ No "proof" at all.. Presumably, a second- or third-hand knowledge of Ancient Greek philosophy and science, through Maimonides. $\endgroup$ Sep 14 at 12:32

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