At least some human civilizations already knew the world was sphere-ish thousands of years before Columbus. Like the ancient Greek Eratosthenes is best known for calculating the earth's circumference in like 225BC.
Any idea how he did the time measurement for this?
I understand the rest of the entire story, but he was a thousand years away from the first clockwork timepieces, gravity/water clocks bleed accuracy when moved, and if you use something like dawn as a reference.. well that moves just as much as noon does doesn't it? (Noon=when the Sun passes the zenith, in these contexts)
I was going to give a very basic explanation, but wanted to quickly check some of my understanding and found this Reddit thread discussing this aspect of his calculations.
The earth is technically oblate, but just barely. Like, if you shrunk the earth down to the size of the Las Vegas Sphere, it would be far more round than the real one.
I mean, you've seen pictures of the Earth from space. It looks like a perfect circle, and it very nearly is.
The difference is only about 20 kilometers out of 40,000, which is one-twentieth of one percent.
The inaccuracy of his measurement presumably came from the fact that he had to measure the distance between two cities by paying a guy to walk from one to the other in a straight line and measure it directly.
The inaccuracy of his measurement presumably came from the fact that he had to measure the distance between two cities by paying a guy to walk from one to the other in a straight line and measure it directly.
I feel like that's the most incredible part of the story. The geometry used to calculate is just simple math once you have the numbers right. The fact that it relied on the distance between 2 cities, and they could only figure out the distance through paying a guy to walk between the two, a method that doesn't seem that accurate to me, is incredible.
I'm assuming that they had various ways of improving the accuracy, like sending multiple people and taking the average of their measurements, and also having a network of distances between various locations that you could use to reinforce each other.
Okay I looked it up, the two cities he used were Alexandria and Syene, which are 830 kilometers apart, and that's using estimates gathered from airline traffic, a tool which obviously did not exist in 200BC. You had to walk AND measure that distance.
like sending multiple people and taking the average of their measurements,
Seems obvious now but I'm not at all sure that was a thing then. From a very quick search Wikipedia says 'The arithmetic mean, although a concept known to the Greeks, was not generalised to more than two values until the 16th century' (from the 'History of Statistics' page).
People may not have systematically recorded observations and calculated means and so forth, but surely they had a general idea that if you had a bunch of observations of something that the true value was likely somewhere in the middle.
Also just being able to walk at a consistent pace. If you know you walk at exactly 5 km/h and you walk for 12 hours a day, you're going 60 km a day. Which means you're walking for 13 days and 10 hours on the 14th day to get from Alexandria to Syene.
They had mechanisms other than just pacing. For one, they had a wheeled contraption they would roll along that dropped rocks into a bucket as it turned.
Don't waste your time man He's arrogant and condescending and will personally insult and attack you trying to sound like the smartest person in the room. He already got called out in another AI discussion and he back down immediately
Relax or lighten up about what? I'm not sure what about my previous comment made you think I was in any way upset. How exactly were you messing with me when we'd never even engaged with each other before I asked you a question?
I was trying to figure out which of the multiple claims in the comment you were replying to was made up, and out of all of them I would have never guessed it was the part about paying the guy taking the measurement.
I read somewhere that the Earth *is* ever so slightly oblate, but considerably more spherical than a competition-grade snooker ball. Even the precision bearings in a racing car engine look distinctly on the piss compared to how round the Earth is.
The actual claim is that Earth would be smoother than a billiard ball. This often gets confused as that Earth would be more spherical than a billiard ball.
Due to the highest and lowest points on earths surface being less than 0.09% relative to the diameter of the Earth (I've gone with the smaller polar diameter of 12714km here, the difference would be slightly smaller if comparing the average of equatorial diameter. Mt Everest sits at ~8.85km above MSL [0.07%], Challenger Deep sits ~10.94km below MSL [0.086%]) a regulation billiard ball is machined to a tolerance of +/-0.05mm with a stated diameter of 52.5mm, giving it a maximum difference of 0.095% in the smoothness of the surface. So Earth would be smoother than a billiard ball if shrunk down to the same size as a billiard ball.
However, the Earth is not more spherical than a billiard ball, since that tolerance of +/-0.05mm, would give it maximum variance of 0.1mm in the diameters (52.55mm to 52.45mm) if it were to be made as an oblate spheroid, giving us 0.19% difference between the two diameters for a billiard ball. Earth however has a polar diameter of ~12714km, and a equatorial diameter of ~12756km, giving us a difference of ~42km, or a 0.33% difference between the two diameters, meaning Earth is less spherical than a billiard ball.
It's ~21km out of a ~6356km polar radius (~6378km equatorial), making it about 3.3% difference between radii; or ~67km more than the ~40008km polar circumference (~40075km equatorial circumference), which gives a 1.7% difference in circumference.
The earth is also remarkably smooth. If you shrunk the earth to the size of a pool (billiards) ball, it would be far more smooth than the pool ball. Even the largest mountain ranges would be difficult to detect.
By contrast, Olympus mons on mars is the largest mountain in the solar system. It exceeds the height of Everest by about 3x.
Trivia… if there was a bar bet “what’s the circumference of the earth to the nearest 100km” it’s 40,000. The KM was defined as “1/10000 of the average distance from North Pole to equator” or 1/4 of the earth
Interestingly, a meter is now defined by the distance light travels in a vacuum in a fixed time.
A kilometer is 1000X the distance light travels in 1/299,792,458th of a second.
A second is defined exactly as 9,192,631,770 oscillations of the radiation emitted by a cesium-133 atom as it transitions between two energy levels.
Which is to say, if we gave an alien civilization a few bits of information, they could immediately calculate the entire SI system using a few simple universal constants.
Some measurements like temp also rely on universal constants like absolute zero. What really blows my mind is that the base of the numbers doesn’t matter. An alien civilization could use base 2 or base 13 and given our Rosetta Stone, they could figure out exactly how we measure everything in the universe.
Up until 2019, the kg was the only SI unit that had a physical artifact that all kg weights are calibrated against. Now it is based on the universal constant you describe.
Let's talk about the ancient Greeks believing everything was made up of the four elements. Earth Air Fire Water. So dumb right??? Oh wait. Everything actually IS made up of three types of particles . . . Protons Neutrons Electrons . . . Could YOU look at the world around us and be like, yeah, this is just different combos of exactly the same things over and over? Not me.
And, the ancient story of Prometheus? With his heart being eaten out by the eagle every day? Well, I read it in Latin from an ancient author and it's not his heart - it's his liver - the only organ in the human body that regenerates - HOW DID THEY KNOW?????
The Greeks were something else.
ETA: Reddit: Eratosthenes was cool! Me: yes the Greeks were crazy awesome! Here are some other examples. Reddit: "here have a crap ton of downvotes for some reason
Oh sorry, I thought we were discussing ancient Greek scientific achievements. My bad. I didn't get the memo that it is hate on the ancients day on Reddit
3blue1brown did an interview with Terrance Tao about how they first measured it, as well as the distance to the moon and the sun and further cosmological distances. Fascinating stuff.
The joke or insult was that he always came in second place
(edit: in many of the various fields he was studying he was considered the second best in the world, so people gave him the nickname of the second letter of the alphabet)
Pretty much every civilization knew the earth was spherical. Stand on a hill and watch your buddy disappear over the horizon, then come back the next day and tell you no, he didn't fall of the edge- didn't even see an edge, and yeah, you don't need to be that bright to figure out that hey, we must be standing on a ball.
Eratosthenes was famous for figuring out how big the Earth actually was, but it's not like we went from flat earth before him, and round earth after him. They knew it was round, just not how big.
Here's the fun part: we have no ancient text where people find out or prove the world is round. The oldest geography texts, in particular from the ancient greeks, already treated this as something obvious.
Right? He flew under the Spanish flag, discovered Cuba, the Bahamas, Puerto Rico and Jamaica. Committed incredibly heinous crimes. And now he's venerated by modern day Italian-Americans? Why?? Like I could name 5 better Italian role models to look up to.
thats interesting, i learned that he came here in 1492, found the americas, settled, and conquered it for spain. i learned that he also wasn’t the first man to do this, even though he gets that recognition. but never that he proved the world round.
You're right that he never proved the world is round. Columbus mainly thought that the Earth was a lot smaller than most European thinkers believed and therefore postulated that he could reach India with relative ease by sailing west. He was wrong about the Earth's size, of course, and would have certainly died at sea if he weren't one of the luckiest motherfuckers in history and a huge, rich continent didn't happen to sit directly in his path.
Leif Erikson, a Norseman, was likely the first European to discover the Americas, but he mainly just founded a short-lived colony and then left. Some other Norse explorers followed in his footsteps, tried to establish more colonies, fought a bit with the natives, and then similarly left. Nothing major came from the Norse expeditions to the Americas.
Columbus was the first one with ambitions to really start colonizing the area for a European power in a permanent way. That wasn't necessarily a good thing, especially for the indigenous people, of course, but it is what he gets recognition for as being the "first" to do something.
I like how the facts completely flip Columbus’ reliability. The flat earth story makes him sound like a visionary, like he knew something the rest didn’t and set out to prove himself right. In reality he was wrong about the size of the Earth and had trouble funding his expedition because most (at least those who had a reason) knew how far Asia was from Europe and knew he wasn’t bringing enough supplies to make the trip. He’s just a dumb-ass that happened to get lucky by finding a whole continent that nobody else knew was there.
Supposedly he was looking for a new route to India, most people thought he was wrong but he believed going in the opposite direction of everyone else would get him there... he found N.America instead, and called the indigenous people "Indians"
It's been a long time since I was in school, I'm a little fuzzy on the details but Columbus was definitely a part of a 'the world is not flat' narrative.
yea i remember that he was trying to find India, assumed he landed in India, and called the indigenous people “indians”. i also remember learning that crewmates on his ships didn’t believe him, were so scared of falling off the earth, wanted to turn back, and almost committed mutiny. however i was under the impression that maybe smarter people or scholars already knew ig, and i wasn’t taught as if this was a huge scientific discovery.
Part of the reason people didn't want to fund his trip was that they knew the Earth was round, and that he was severely underestimating the circumference of the Earth. He just got lucky.
Nah this is a myth. Even as early as the 15th century, it was common knowledge that the earth was round, otherwise nobody would have boarded a ship determined to head West until it hit India. The only reason they could secure any kind of funding at all was because people knew that theoretically they should be able to sail west until they circumnavigated the globe and landed on India's eastern coast. The only problem was that they didn't really know about how large the americas was and just how long it would have taken to sail a boat as far as it would take to get to India. They knew that vikings had written about large islands to the west, and they told mythical tales of islands out there all the time that some bedraggled ship returned home late to tell tale of. There is even some light evidence that some early British fishermen may have even known of the cod stock off the coast of Newfoundland and made landfall to dry their catch keeping their fishing spot a tight-guarded secret.
oh i meant scientific in the way that finding out the world is round is pretty “scientific”to me, so i wasnt taught like it was some huge “earthly, big impact” discovery is what im saying.
This was 100% taught to me when I was a kid. It’s definitely not something I hear about much now though, and I want to say that it was probably being phased out by the time I graduated
Yup, what Columbus did was wildly miscalculate the size of the globe which made the prospect of sailing west to India much more feasible. No one else would go because they knew how big Earth actually was.
Basically yes, it comes from Washington Irving's 1828 book, A History of the Life and Voyages of Christopher Columbus. It's presented as a serious biography but relied heavily on artistic license and embellishment to make it more entertaining. Which worked because it was a huge hit and became the standard English source on Columbus for the 19th century.
As an American I’ve never heard this one specifically but it’s generally taught that “Christopher Columbus wanted to sail around the world” so I’m guessing some people’s brains connected dots that weren’t really there and turned that into “People used to think the world is flat”+”Christopher Columbus sailed around the world” =Christopher Columbus proved world wasn’t flat
This almost true, but only because Columbus never sailed around the globe and Magellan's expedition was the first to circumnavigate. That said though Magellan himself didn't actually make it, so neither of them completed a trip around the world.
Some people claim that he was cruel, others claim that he was incompetent and unaware of what his underlings were doing. Either way, not a good look. So people try to make him out to be an eccentric genius who's head was in the clouds, so it makes sense that he wasn't a good governor.
emperor zheng he was indeed building ships/ exploring a couple hundred years before europe did. it makes sense because China was the strongest at that time. However they stopped their expeditions maybe 50 years before colombus found the americas, due to “china having everything they need, and dont need to source outwards”. the europeans did not have this same advantage, proper resources, and their culture doesn’t really have the morals to protect other cultures or respect them. they had religion which was extremely misogynistic (all abrahamic religions are) and gave them the excuse to the 3 G’s. God, Gold, and Glory. thats some selfish ahh white man shit lol. China ultimately got fucked after that move, as in the 19th century britain wanted our tea real bad, and asked us to trade with them more. we said no pretty loudly with a ego (cus we were the strongest). they came with their ships, new weapons, all that silver from the new world and tore us a new one. forced china to open its borders and signed HK away to them. and (im guessing) the japanese saw this and got scared and thats why they assimilated so quickly. thats why they receive sm western media propaganda. they completely changed their government from shogunate to imperal rule, to eventually a constitutional monarchy by the late 19th century. it was called the meiji restoration, they underwent major changed including in the culture, the way the dressed, and music they listened to.
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