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My question embraces history, cosmology and astronomy, I hope this is an appropriate forum to ask it, if not I apologise and hope to be re-directed.

I have read, but lost the reference, that when the remnant of Magellan's expedition returned in September 1522, their log showed a date the day before that of the inhabitants of the port where they landed. This is important evidence that the Earth orbits the Sun, but it is not mentioned in any reference to the voyage that I can find. Please, does anyone have more details, and where I can find out more about it?


Edited to correct an error , it was a day lost, not gained

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    I don't see how this would in any way constitute evidence of which body is doing the rotating. Either scheme would have produced the same effect. – T.E.D. Jun 3 '16 at 13:22
  • Ok T.E.D, but It does not really matter whether we consider that the Earth orbits the Sun or that the Sun and everything else goes round the Earth, it's just that the former makes the maths for all the other thingss so much easier. – Harry Weston Jun 3 '16 at 16:23
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    It could arguably be used as evidence that the earth is round, but the evidence of "well I just sailed all the way around it" is much more convincing, and easier for the layperson to understand. It's definitely not evidence that the Earth orbits the Sun. I mean, the Earth does orbit the Sun, there's no controversy about that - and I'm sure T.E.D. wasn't attempting to argue that point - but Magellan's logs don't indicate that in any way. – Tin Man Jun 3 '16 at 17:30
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    @Jeeped, it doesn't prove that, either. A Sun orbiting the Earth, an Earth orbiting the Sun, and an un-moving Earth spinning next to a stationary Sun all produce the same extra day. All the extra day does is eliminate a number of flat-Earth scenarios. (In order to distinguish a heliocentric system from a geocentric system using astronomy, you need to measure stellar parallax or aberration of light, both of which are far too small for instruments of Magellan's day to detect.) – Mark Jun 3 '16 at 19:49
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    @Jeeped, no, it only proves the Earth doesn't experience the same solar time across the entire surface. You'll get the same one-day discrepancy if the Earth spins, or if the Sun orbits an unmoving Earth in the opposite direction of the proposed spin. – Mark Jun 3 '16 at 20:02
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The first ship to successfully circumnavigate the world was the Nao Victoria. It was originally part of Magellan's fleet. All of the other ships (the Trinidad, the San Antonio, Concepción and the Santiago), Ferdinand Magellan himself, and most of the sailors of the Victoria had already either been killed, or turned back before this. When the Victoria finally returned to port, under the command of Captain Juan Sebastian de Elcano, they discovered, even though their logs were kept meticulously, that they found they were a day behind everyone else. This, eventually, led to the establishment of the International Date Line.

Source: Laurence Bergreen, Over the Edge of the World: Magellan's Terrifying Circumnavigation of the Globe, Harper-Collins Publishers, 2003.

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