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June 11

When did humans realize the hemispheres have opposite seasons? How did they react/explain it?

I have put no effort into answering this question myself, sorry if this is answered somewhere obvious. JoelleJay (talk) 06:14, 11 June 2022 (UTC)[reply]

The more basic question might be, When did humans realize there were two hemispheres? (i.e. Northern and Southern) --←Baseball Bugs ^{What's up, Doc?} carrots→ 07:24, 11 June 2022 (UTC)[reply]

Spherical Earth tells us that "The earliest documented mention of the concept dates from around the 5th century BC, when it appears in the writings of Greek philosophers". The Greeks, being seriously into geometry, knew that a sphere has hemispheres. HiLo48 (talk) 08:03, 11 June 2022 (UTC)[reply]

Thus it seems reasonable that those same Greeks would have calculated how the seasons would work in the southern hemisphere, i.e. that the solstices would occur in opposite seasons. --←Baseball Bugs ^{What's up, Doc?} carrots→ 08:57, 11 June 2022 (UTC)[reply]

Assuming they had a motivation to calculate it. Since the Greeks never travelled to the Southern Hemisphere it might never have occurred to them to ask when the seasons occurred there. Blueboar (talk) 10:20, 11 June 2022 (UTC)[reply]

Maybe this question would be better suited to the Science desk? The Greek astronomer who calculated the size of the earth by measuring the noon elevation of the sun at two sites on the same longitude and the number of stadia between them pointed out that the pole would have six months of daylight followed by six months of continuous night, and fairly obviously if the sun is continuously above the horizon at one pole it's continuously below the horizon at the other. 2A00:23C3:FB80:7C01:744B:6FCA:C5C0:3524 (talk) 10:15, 11 June 2022 (UTC)[reply]

Erastothenes#Geography puts a timeframe on it.2A00:23C3:FB80:7C01:744B:6FCA:C5C0:3524 (talk) 10:47, 11 June 2022 (UTC)[reply]

Centuries earlier, Aristotle had already presented the argument that the Earth is round by considering that the Earth's shadow cast on the Moon during lunar eclipses always has a circular border, regardless of the relative position of the Sun; the only shape that has this property is a sphere. His treatise On the Heavens is the oldest known text with the argument, which can hardly have been new, but may not have been so cogently put forward earlier. Erastothenes' invaluable contribution was to determine the size of this sphere, which cannot be deduced from observations of eclipses. --Lambiam 12:27, 11 June 2022 (UTC)[reply]

As for actually experiencing it, Bartolomeu Dias discovered the Cape of Good Hope in 1488. The cartogropher Fra Mauro recorded an earlier voyage around the cape by an Indian "junk" in 1420, but I don't think India has the same temperate seasons that we have in Europe. Alansplodge (talk) 11:28, 11 June 2022 (UTC)[reply]

Yes, he was a monk, but be careful how you describe him.

I wonder if the "Indian" junk might be Chinese -- see Ming_treasure_voyages#Fifth_voyage or Ming_treasure_voyages#Sixth_voyage... AnonMoos (talk) 18:17, 11 June 2022 (UTC)[reply]

Herodotus wrote about the Phoenician circumnavigation of Africa (or Libya, as he called it) during the reign of Pharaoh Necho II, around the turn of the 6th century BCE. He didn't mention a reversal of seasons (even though the journey took two whole years), but did mention the Phoenicians' report of the sun being on the wrong side of the sky: "The Phoenicians took their departure from Egypt by way of the Erythraean sea, and so sailed into the southern ocean. When autumn came, they went ashore, wherever they might happen to be, and having sown a tract of land with corn, waited until the grain was fit to cut. Having reaped it, they again set sail; and thus it came to pass that two whole years went by, and it was not till the third year that they doubled the Pillars of Hercules, and made good their voyage home. On their return, they declared – I for my part do not believe them, but perhaps others may – that in sailing round Libya they had the sun upon their right hand. In this way was the extent of Libya first discovered." — Kpalion^(talk) 11:35, 11 June 2022 (UTC)[reply]

The disbelief Herodotus reports shows that in his days the notion that the Earth is shaped like a ball was not common among people of learning. I think that the statement that "The earliest documented mention of the concept dates from around the 5th century BC, when it appears in the writings of Greek philosophers" in the article Spherical Earth is therefore false. I cannot find any such early "documented mention", or a concrete reference to one in the cited sources. --Lambiam 12:52, 11 June 2022 (UTC)[reply]

Perhaps a Template:Dubious is in order there. Alansplodge (talk) 13:39, 11 June 2022 (UTC)[reply]

Some information at Anaximander#Cosmology: its curious shape is that of a cylinder with a height one-third of its diameter, but furthermore, according to Diogenes Laertius (II, 2), he built a celestial sphere, and It is a little early to use the term ecliptic, but his knowledge and work on astronomy confirm that he must have observed the inclination of the celestial sphere in relation to the plane of the Earth to explain the seasons. Here's the quote from Diogenes Laertius: [Anaximander said] that the earth lay in the middle, being placed there as a sort of centre, of a spherical shape. So that's a (second-hand) quote from the 6th century BC, in fact. He also made a globe, if we believe Diogenes Laertius (and the translation). Card Zero (talk) 14:55, 11 June 2022 (UTC)[reply]

A cosmological model with a non-spherical Earth is perfectly compatible with a celestial sphere. I interpret the quote by Diogenes Laertius as stating that in Anaximander's model the Earth was placed in the centre of something of a spherical shape, and not as ascribing a spherical shape to the Earth itself. Aristotle commented on Anaximander's model but mentions no such thing. --Lambiam 10:33, 12 June 2022 (UTC)[reply]

I don't know if that necessarily shows that Herodotus didn't accept a spherical earth, just that he hadn't realised what that would mean for the relative position of the sun. Iapetus (talk) 09:48, 13 June 2022 (UTC)[reply]

I guess a different way of asking this would be, when was the first time someone reported that the hemispheres had different seasons, based on their personal experience? Would typical navigators have even been familiar with the theoretical basis of seasons (i.e. even if they were aware the world was a sphere, would they have put together that the seasons were related to hemispheric position)? And would they have even known when they crossed the equator? They would certainly have known it gets warmer as you go south in the northern hemisphere, but if they left the north in, say, late fall and it just kept getting warmer/staying warm/days were long even after passing the equator, they could just think south=hot, more south=also hot and not connect it to seasons. Basically you'd have to have someone from the north going south in the spring and managing to get far enough south to experience winter, or sticking around in like South Africa for a full year. So there must be an earliest known recording of this somewhere, right? JoelleJay (talk) 21:08, 11 June 2022 (UTC)[reply]

An earlier link discussed the circumnavigation of Africa by the Phoenicians. The voyage took three years, and during it they replenished their supplies when autumn came. 89.240.118.45 (talk) 11:34, 12 June 2022 (UTC)[reply]

Yep I noticed that link, but there wasn't anything about them specifically noting the season difference. JoelleJay (talk) 01:14, 13 June 2022 (UTC)[reply]

They can hardly not have noticed it themselves, but may not have been believed when reporting it. --Lambiam 10:38, 13 June 2022 (UTC)[reply]

The relation between the position of the sun in the sky and the temperature is quite obvious and from basic geometry it's quite obvious that the position of the sun on the southern hemisphere must be the opposite of the northern hemisphere, assuming you understand that the earth is a sphere (which is quite obvious too, if you understand geometry and watch some distant mountains). Would people have believed that the season with short, dim days would be the hot season in the other hemisphere, even while believing the sun is the source of heat? I don't think so, but not everybody is very good at geometry. Most learned people (including Herodotos, I think) specialise more in humanities than in science. Even today there are many people, not believing in a flat earth, whom you have to explain that the seasons are opposite on the other hemisphere.

I've read well-sold stories by smart authors in which the hero walks to some mountain. The hero can see the mountain for days, even weeks, before finally reaching it, while walking at a considerable speed. Then I begin to calculate: h≈d²/(2R). I find that that mountain is at least 7000 metres high. Next, the hero climbs the mountain within a day.

Most people just don't understand geometry. Those who did would probably have believed, even deduced beforehand, that the seasons on the opposite hemisphere were opposite. And just as today, some people just don't believe science. PiusImpavidus (talk) 19:01, 13 June 2022 (UTC)[reply]

It's easy to see when you cross the equator. On the northern hemisphere, the stars rotate counterclockwise around the north celestial pole. When you move to the equator, the north celestial pole goes to the horizon. On the southern hemisphere, the stars rotate clockwise around the south celestial pole. Navigators have used the stars for ages to find north and south. And if you watch the constellations visible during the night, you can tell what season it is at home. PiusImpavidus (talk) 19:10, 13 June 2022 (UTC)[reply]

Not to make this even more complicated, but I think the question is more complex than most answerers have taken into account. In terms of solar and sidereal observations, yes, there is a switch that occurs so that the two hemispheres are in opposition. But season means much more than that. As that article points out, the traditional four-season reckoning is very far from universal. In the tropics, it's more like two seasons (wet and dry), of various lengths. Other areas recognize six seasons and it's not just semantics. And, because land distribution is heavily skewed to the north, a high percentage of southern hemisphere land falls into those tropical/equatorial areas. It's not until you start getting into the relatively extreme portions of the southern hemisphere that you start seeing an inverted four season schedule. In other words, it's not so straightforward. 64.235.97.146 (talk) 20:14, 13 June 2022 (UTC)[reply]

The southern rim of Herodotus' Libya was equally far from the equator as Phoenicia, with a very similar climate. --Lambiam 04:04, 14 June 2022 (UTC)[reply]

We can agree that the inverted seasons must have been noticed by early navigators, and I can see how they would have understood the geometric basis for it. But surely someone at some point noted this, right? There had to have been someone on a ship who was both literate (or talked to people who were) and not aware of how seasons worked, whose testimony survived long enough for us to know about it? Or was this phenomenon just so expected and unremarkable that no one bothered to reference it? JoelleJay (talk) 05:02, 14 June 2022 (UTC)[reply]

Here's a northerner (a pilot from Portugal) noting different seasons c. 1520-1540: The summer months are December, January, and February, when the heat is excessive, and the atmosphere being continually loaded with vapour, occasions the air to feel like the steam of boiling water. The shores of this island abound in many kinds of fish, and, during the months of June and July, the inhabitants catch a kind which they name le chieppe, which are singularly delicate. In the seas between this island and the coast of Africa, there are prodigious multitudes of whales, both of the large and small kinds.--Should you, Sir, be unsatisfied with my ill-written and confused information, I beg of you to consider that I am merely a seaman, unpracticed in literary composition. 70.67.193.176 (talk) 16:46, 14 June 2022 (UTC)[reply]

In that passage, the seaman is describing the climate of the island of São Tomé, which lies on the northern hemisphere, just north of the equator. (Ilhéu das Rolas, 2 km south of São Tomé, straddles the equator.) --Lambiam 17:43, 14 June 2022 (UTC)[reply]

He is an example of what was asked for immediately above, "someone on a ship who was literate and not aware of how seasons worked and whose testimony survived". He is astonished that seasons are different elsewhere than in Europe. 70.67.193.176 (talk) 19:04, 14 June 2022 (UTC)[reply]

This is the closest we've gotten to someone actually remarking on "seasons being different", but still doesn't fully address what I'm asking since what he was experiencing was just the equatorial climate, not a true inversion of seasons. JoelleJay (talk) 20:53, 14 June 2022 (UTC)[reply]

You are correct that it is far more complicated an answer because the assumption is wrong to begin with. The two hemispheres do not have opposite seasons overall. They are opposite as you get away from the equatorial region. Near the equator, you have rainy and dry seasons, not winter, spring, summer, fall seasons. Therefore, this would not be something you'd notice if you lived on the equator and walked from one side to the other. You have to travel, very quickly, from a location far enough to one side to have snow and get to the opposite side to see that it is warm. Once communication between those areas was established and they had a common calendar, it would become obvious that the seasons were switched. It is certain that various long-distance sailing trips would notice that the weather was wrong, but did they recognize it as a normal wrongness? 12.116.29.106 (talk) 15:56, 14 June 2022 (UTC)[reply]

Yes, this is essentially what I was asking here: Basically you'd have to have someone from the north going south in the spring and managing to get far enough south to experience winter, or sticking around in like South Africa for a full year. So there must be an earliest known recording of this somewhere, right? JoelleJay (talk) 20:42, 14 June 2022 (UTC)[reply]