When did Europeans first discover the equator and that south of it the seasons are reversed? That must have come as a pretty significant shock to them, no?
Lope Goncalves was the first European navigator to cross the Equator, off the coast of Gabon around 1473-74. Bartolomeu Dias reached the Cape of Good Hope in South Africa in 1588. However, there was not enough seasonal variation (at least in temperature) in either place to make it clearly evident that the seasons were reversed.
The first European to spend enough time in a temperate area of the Southern Hemisphere to realize that the seasons were different was Ferdinand Magellan, who “wintered” in Patagonia in southern Argentina, actually the southern summer, in 1520.
Before Magellan - was their any prediction based on science that the seasons would be flipped? Had communication with southern hemisphere cultures given them evidence of the phenomenon, even if they hadn’t experienced it themselves?
It was probably deduced long before they actually traveled there. The ancients knew that the Earth was a sphere, knew its size, and knew that the Sun was north of average in June, and south of average in December. It’s not too big a leap from there to realize that, if there are any lands to the far south, they’ll have their summer when the Sun is south, and winter when it’s north.
Educated people knew that the Earth was a sphere since back before the ancient Greeks and Romans, and had pretty good ideas of how big the Earth was. And they knew that things were colder as you went north and hotter as you went south. But you’re correct that they hadn’t been to, or South of the Equator. Nobody knew just how hot the Equator would be. Since the Sahara desert is south of the Mediterranean some people speculated that the Equator would be too hot to support life, and if there was a southern hemisphere there would be no way to get there.
I have no idea how this worked over in Asia. Seems like it would be pretty easy for Chinese traders to work their way south to Indonesia and cross the Equator there, there are records of Chinese sailors reaching India in the 2nd century, and they would have had to cross the Equator to get around the Malay Peninsula. Whether they realized they had crossed the Equator is another story.
Before the Portuguese voyages down the west coast of Africa, there was no contact between Europeans and southern hemisphere cultures.
According to Herodotus, the Egyptian king Necho (about 600 BC) sent a Phoenician crew to circumnavigate Africa. That this actually occurred is supported by the observation that they had at some points the sun to their north, something that would only occur if they had crossed the Equator. However, that was the extent of western knowledge of lands south of the Equator (and in fact the story was disbelieved by the geographer Ptolemy).
But the Europeans had contact with Arabs, who did have connections with sub-Saharan Africa, no?
Chinese traders would have certainly crossed the Equator to round Malaya, but wouldn’t have gone much south of there, and would have remained in the tropics where seasonal changes were not very apparent.
Here’s a map of the voyages of Chinese admiral Zheng He in the early 1400s.
Arab traders would also have crossed the Equator on the east coast of Africa, but not generally (if ever) south of Mozambique.
The Sahara is well north of the Equator (in fact, much of it is in the temperate zone), as are the cultures the Arabs would have mostly been in contact with. As I mentioned, the Arabs would have crossed the Equator along the east coast of Africa, but that was very far from Europe.
Anything Europeans would have heard about areas south of the Equator would have been the merest hearsay and indistiguishable from myth.
Did they know that the Earth is tilted on it’s axis?
Well, they wouldn’t have described it as the Earth being tilted, but yes, they knew that there was an angle between the Earth and the plane of the Sun-Earth orbit.
Even knowing that it would be easy to miss out on the effect on the local climate. If there was no observation of the differences between the hemispheres no one may have bothered considering the subject.
This isn’t technically true - anywhere in the tropics will see the Sun to the north at some times of the year (and to the south at other times). However, if you believe that the Phoenicians left Egypt via the Red Sea and returned via the Mediterranean, then the only plausible explanation is that they went round Africa - it’s not like there are any short cuts.
(By a quirk of geometry, anywhere inside the Arctic circle will also see the Sun to the north at certain times of the year. And Europeans were undoubtedly aware of the Midnight Sun long before any of them crossed the Equator)
Nitpick: At any point south of the Tropic of Cancer, the sun crosses the meridian to the north of the zenith on at least one day per year; this happens on or around the summer solstice, when the sun is at maximum declination. [On posting, I see that Merrick has made the same observation.]
Magellan spent the first “winter” (March to October?) camped out not far from the entrance to the Straits of… Magellan. Either he figured it out pretty fast, or already anticipated that the North’s summer was the cold time down south.
Of course, only the more southern extremes of South America, Australia and New Zealand are significant land areas with real winters (although with Australia that may be debatable, except maybe Tasmania). I understand it can snow sometimes in South Africa. So just going south of the equator a bit would not be enough to demonstrate real climate reversal.
Interesting fact: William Heschel, the musician-turned-Royal-Astronomer who discovered Uranus (and wanted to name it “George”, after his Royal Patron) made it his life’s work to accurately map the Northern Hemisphere. His son, John Herschel, also an astronomer (also one of the inventors of photography – he invented “hypo” fixer --, a big fan of the camera lucida, inventor of a photometer, and almost became the first calculator of the diffraction due to a circular opening – George Biddell Airy did it better and earlier), moved to South Africa to complete his father’s work by mapping the stars of the Southern Hemisphere.
But was it that deduced logically/scientifically or was it part of the assumption (may be spurious*) that southerners did everything upside down like walking on their hands or trees with branches in the ground and roots in the air.
*Evidence of this thinking today - thinking the Coriolis Effect impacts the way water swirls in a toilet bowl.
To be clear, I didn’t say that they actually had that belief, just that they could have deduced it logically. I don’t know for sure that they did.
I’m not sure how much he figured out in advance, but he stopped where he did because he was being hit by increasingly frequent storms, the weather was becoming freezing cold, and the days were getting very short.
No, but they already knew from the Greek’s about the change from tropical to temperate to (ant)arctic conditions as you go from equator to south pole…
see Pomponius Mela - Wikipedia
Basically the answer to the OP’s question is “astronomy worked it out first, then they went and found it was true … nothing observed was somehow disturbing to astronomy”.
The size of Australia had been debated, but it is at least a continent with significant larger plate size under the seas.
Sydney Australia has seasons, the main cause is that the high pressure systems come one after another in summer, not many fronts, and in winter its one low pressure ( cold front from the south) after another…