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Where did Ferdinand Magellan leave from?
Ferdinand Magellan's fleet left Spain on 20 September 1519, sailing west across the Atlantic toward South America.
When did Ferdinand Magellan leave?
Ferdinand Magellan's fleet departed on 20 September 1519.

Question: what was the trip like across the atlantic?
Self-contained rewrite: What was the trip like across the Atlantic for Ferdinand Magellan?