Time difference and duration

Exactly, and since that even exists in reliable historical sources centuries BC its well, normal to know it i guess you could say.

Erastothenes did that ~250ishBC, might you be mixing him up with St Brendan from 5th-6th century?
Well its not like i have every saint or ancient monk in my head... That might get a bit crowded... :stuck_out_tongue:

Sure, if you have the eyes of an eagle!

A 20 foot (6 m) mast becomes visible 6 miles (10k) away - and that's a thin mast. Bigger masts only make the range further.

So, while it's "possible", I'm not sure that anything smaller than a large ship could reveal the effect, and then it might not be obvious.

I'm on the water all the time, and a ship is either close enough to see the whole thing with the naked eye, or far enough away that you can't tell.

But that aside, yeah, the educated probably knew the world was round, tho' even then not all of them would agree on that.

Have to disagree, unless all you´re seeing are tiny boats rather than ships, it is very noticeable. Especially when concerning SAILING ships. Which is sort of the majority here.

You wont be looking at the mast, you will be looking at the sails, and a 6m mast isnt that big.
For an extreme comparison, my 3m sailing boat has a 5m mast ( and yes its not very steady, but darn its fast! ).

But the thing is, you are seriously forgetting looking the other way around. Which is how its specifically mentioned in historical texts, how sailors could see MOUNTAINS coming "up" from behind the horizon.
Read accounts from 16th century onwards that talks about sighting ranges with and without assistance and how you could estimate a ships distance from you different ways.

Ahh... landscape. D'oh! That's true, and I don't do that much "over the horizon" sailing.

(A 6 m mast is not that big, true, but taller masts are even further away when they crest the horizon. And as a rule a dark mast can be seen before a pale sail, depending on the background sky. I've seen some big sails, but never "coming over the horizon", not without magnification.)

MM had mentioned "anyone living in a coastal city", and that was the image in my mind. But sailors have an entirely different perspective.

But then again, what educated person would believe a sailor's stories? :wink:

True, I was a little loose in language saying merely "coastal city". Perhaps Port city is more accurate, the sort that would be dealing with large ships all the time. And actually, my knowledge is second hand. I am just going by what my dad once told me, which is something he himself had learned from the navy.

Yep. What "sailors" know is not the same as what "port folk" know. Just as what farmers know is not the same as knowledge for city folk, where they may go to sell their crops/animals. Because the two rub elbows regularly doesn't mean they believe or value the others' experience.

How long were ermine considered different animals than stoats, at least by some "educated" members of the academia? Despite any trapper knowing better - such commoners were "clearly just ignorant".

Such "country wisdom" and common knowledge is (even still) often disparaged by people who think their status gives them universal superiority. Thus medieval scholars had long discounted many tales of "sailors" because, despite the stories being consistent and continuous, they were "just sailors". :wink:

No, trust me on this, you WILL see the sail looooooooong before you can make out the mast that the sail is attached to.

Get to some place that is used as goal for some race with old sailing ships(and i mean BIG SHIPS, not the kind of oversized boats like in Americas cup or similar), with or without magnification you will see a white speck at the horizon, slowly moving UPwards until you see the hull.

You really dont need to go very far at all before the effect is very clearly visible. A few hours away from land and it gets totally obvious, even without hills or mountains on the coast, if there´s any of that as well the effect is outright painfully easy to see. Which to me means that its very likely that people saw this within days after the first person went more than an hour or two offshore.

Well obviously NONE of course! :wink:
Which might mean the first time its written down really IS the first time someone has taken it seriuosly(300+ish BC or something like that).
However, how likely is that? Not at ALL would be my guess, even if 99% of scholars didnt listen, there is always the oddball standing out from the crowd, in all ages and that would be enough to "spread the news" to take it into consideration and debate at least. The fact that we dont know when that first happened, doesnt really say much.
As best as we know, people knew or suspected the earth was spherical at least several hundred years BC, further than that we cant go sadly for a complete lack of information...
Oh such a pity loosing the library at Alexandria... (and now THERE is a story in the making for anyone playing AM, trying to located either remnants of the library or perhaps there was a "backup site" or..., its a great plot device, and if found, the biggest problems are conservation and such abundance of scrolls and books that its hard to find both what you want to read about and worse still to find something GOOD on that subject).

Well, if 150' (45m) mast isn't enough, then you're talking about a very narrow and (relatively) modern period, the Golden Age of sail power.

The sort of boats contemporary to Ars are not the size you're talking about.

Eh, an hour or two is only 5-10 miles at most, possibly less without perfect wind. And at that distance, the only detail that is lost is the first 10'-15' or so - and that's measured from the tideline. Buildings and distinct landmarks would be higher up - and at that distance, buildings are going to start to get indistinct anyway (again, depending on the weather and amount of moisture in the air.)

Same with lights at night - altho' in fact they tend to appear "suddenly", it's hard to know for a fact that's because of the curvature of the earth, and not that a fire hadn't just been lit, or a window just opened.

I'm not saying that you can't see it, but that it isn't as glaringly obvious as you make it out. Especially if the matter is in debate. Today, we know what we're seeing, so we see it - then, if you can't see something at that distance, it's probably because "it's too far away"! What, you think it dropped over the far side of the horizon or something? :wink:

Evidence from ancient Egypt shows that the early Egyptians already knew how to assemble planks of wood into a watertight hull, using treenails to fasten them together, and pitch for caulking the seams. The "Khufu ship", a 43.6 m long vessel sealed into a pit in the Giza pyramid complex at the foot of the Great Pyramid of Giza in the Fourth Dynasty around 2,500 BC, is a full-size surviving example which may have fulfilled the symbolic function of a solar barque. The ships of the Eighteenth Dynasty were typically about 25 meters (80 ft) in length, and had a single mast, sometimes consisting of two poles lashed together at the top making an "A" shape. They mounted a single square sail on a yard, with an additional spar along the bottom of the sail. These ships could also be oar propelled.

I might add that i have several books with pictures of historical ships and they certainly do NOT have short masts even if they might not always have masts taller than their length as is common in the last half-millenia at least.
Sorry couldnt find any more specific early online references at the moment.
Still, 20-30m masts are commonplace, 30-40m exists.

I think i will count my own real experience with this as rather more weigthy than you´re guesses.
And for the reference, in 2 hours with my boat, even in "ok" wind thats more like 10-12nm. It IS a nastily unsteady boat, but once you get it going 6 kts is slow for it, reaching 10+ kts isnt impossible at all.

However, thats beside the point, because even 10 miles out, you DO see that low hills or houses start "sinking into the water", already at that range, especially if YOU are low to the water the effect is visible. 10-15´ is totally obvious enough. Far more than is needed for the effect to be visible.

Yes it is that obvious. Or do you have a good explanation why you would otherwise loose sight of lower parts of houses at rather short distances?

Actually thats biased/prejudiced thinking, saying they wouldnt see it because they´re to undeveloped or whatever, it doesnt make sense. Especially since there is NO KNOWN "ancient excuse" for this effect. That also points strongly towards it having been understood so long ago that any excuses were lost totally since.

  1. Ancient ships have proportionally shorter masts, due to technology. Doesn't matter how long, but how tall.

  2. We aren't talking about knowledge in Ancient Egypt, but in Medieval Europe. Lots of progress was lost, and opinions differed in ME. Rumour and superstition outweighed "knowledge" in many social circles.

  3. Sorry, but you're the only one "guessing" here, and incorrectly - I have sailed for decades. And you, I'm sure, know that while 5-6 knots is good for a small boat today, it was almost unheard of "back then" (again, depending on the wind.) With larger boats we get back to the diff between sailors and townsfolk.

  4. 5-10 miles is not "short distances". And any boat out that far is going to lose sight of those details. A bulk in the distance, sure, but knowing that you can't see the bottom third of a building? I'm not convinced. From real experience.

If a building is 10' above the water level (a reasonably conservative distance), you don't even start seeing it disappear until 5 miles. And except on calm days, the wave action makes such incremental judgements very difficult to achieve, much less comprehend.

Far more often than not, by the time an entire building "sinks", it has long since been lost in the distance.

  1. It's not biased, it's the simplest explanation. Individuals don't tend to think outside the box when they don't have to, when their culture tells them something different. Ask the ancient Central American cultures about the wheel.

You're acting as if anyone on a boat would immediately jump to the conclusion that the world must perforce be round, or be a complete dolt. ~That~ is biased, by our comfortable and patent understanding of the fact, by our privilege of having seen incontrovertible images of the world from space, from everything we've been taught all our lives. In a world without such knowledge, where the reverse might largely be rumoured, and rumour and superstition carries as much (or more!) weight as "book knowledge", it's a huge leap.


Think about it carefully once more, please.
Now, if you failed to realise it, we are talking thousands of years, multiple cultures interacting and literally MANY thousands of ships from time to time moving in such a way that the effect is visible. Its not a matter of "everyone must see it", its a matter of so many seeing it again and again and again and again that it WILL be blatantly obvious OVER TIME.

Then i must be impolite and ask if you have either poor eyesight or have been out on the water just someplace with more than average pollution in the air, because really, any and almost every time i have been out anywhere further than near the coast, it DOES become quite obvious.

Yes but you dragged size of the boat into it as well, guess ill have to dig up one of my books on nautical history.
Ok lets see what we got in Europe early 13th century...

Hanseatic kog, rather a standard average thing nothing fancy, 27m long roughly 25 high mast, 7.2m width, estimated sail area 185sqm.
A Venetian ship from 1268, 26m long, 6.45m wide, very roughly ~25m high masts(2) with latin-rigging.
A Saracen Dromon from late 12th century is mentioned as being "over twice the size our own ships"(crusaders point of view, 3rd crusade, 3 masted warship).

Then, once we hit 14th century we start seeing the appearance of the Karack, which as a norm has mast higher than its own length and is on average a bit larger than preceeding ships, up in north Europe the Holk that replaced the kog and the knarr around a century before the karack appeared was probably very similar, except built more primarily as a trader while the karack was more multiuse.
A slightly later karack is mentioned with measurements, 37m long 10.2m wide, probably around 45m tall main mast.
After that the shipbuilding revolution appears between roughly 1400 and mid 1500s and gives little useful information.

Ah yes, an earlier example of a VERY common ship, a Roman wheatship from one of the first centuries AD, 45-55m long 14-16m wide, 10-13m deck to keel, very roughly 25-35m high mast.
One of the sources mentioning one of those btw, Lukianos, at the same mentions the man at the steering oar being a old little man named Heron. :slight_smile:

Oh and just as a sidenote, the Nemiships might be mentioned, Roman, from roughly same timeframe as the wheatships, and found on the bottom of an inland lake close to Rome, these 2 ships were 71 by 33m the other 73 by 14.4m.
Since you were so displeased by my mentioning Egyptian ships i mean. Because there were absolutely no connection between medieval Europe and earlier and Egypt of course?

Just to add to that ill include some of the biggest known ancient Egyptian ships as well, or at least the ones we have knowledge about the size of, because an Egyptian, Ineri mentions building a ship to transport giant obelisks( the ones that later ended up in Paris and London), that ship was 63 by 21m, later however Hatchepsut did something similar but with obelisks roughly twice as heavy, 350 tons each and 30m long, but no direct knowledge exists of the size of the ship carrying that.

Still, you are by far too dismissive of what is in fact KNOWN realities about history, because of your conviction of "-they couldnt do that", "-they couldnt know that".
You might want to take a good look into ancient Indian astronomy just for fun...

Edit: Oh and of course i forgot one of the most blatantly obviuos signs of this knowledge being standard...
The fact that lookouts were placed at the top of the mast well before medieval times(because, as its stated, from there they could see ships further away than you could on the deck), and this practise became the norm during 11th and 12th century thanks to inventions allowing better supports for the mast.
Before that, fore and aft "castles" or similar constructions often held some form of RAISED lookout position.

Just droping in to say that I have seen this effect going from Barcleona to Menorca (one of the Balearic islands) tewice. Once in a 20 m boat and once in a ferry. The island and the hills of barcelona (no more than 600 m high) "appeared" over the horizon when approaching thyem, and sank into the sea when moving away from them. That is a fairly short route and has been heavily travelled quite frequently during the last 2500 thousand years, at least.

Take in mind that the Greeks live in an archi`pielago. they were seeing it all the time. Philosophers moving between islands saw it regularly it would seem, so they wopuld wonder why, methinks :slight_smile: It is not only that sailors saw it, but educated people travelled in those ships as well

No idea if this was common knowledge in the middle ages, but I would not think that educated people could find information on this fairly easily if they bothered to search for it. A lot of them woulod not even care aboyut it, but some must have thought a little bit on the issue



I was standing on the shore of Lake Michigan last night. Lots of ice close to shore, but all floating and broken up by the waves lapping over it (it's a big lake, it has cresting waves).

Anyway, the thing is a massively huge lake, and impossible to see all the way accross. It is longer than wide, and looking left to right, it appears to me that the horizon itself is curved.

(Lake Michigan and Lake Superior share the same bed, and technically are the same lake. Together, they form the worlds largest body of freshwater).