How Eratosthenes calculated the Earth's circumference
HTML-код
- Опубликовано: 9 сен 2016
- In the mid-20th century we began launching satellites into space that would help us determine the exact circumference of the Earth: 40,030 km. But over 2000 years earlier, a man in Ancient Greece came up with nearly the exact same figure using just a stick and his brain.
--------------------------------------------------
Follow BI Video on Twitter: bit.ly/1oS68Zs
Follow BI on Facebook: bit.ly/1W9Lk0n
Read more: www.businessinsider.com/
--------------------------------------------------
Business Insider is the fastest growing business news site in the US. Our mission: to tell you all you need to know about the big world around you. The BI Video team focuses on technology, strategy and science with an emphasis on unique storytelling and data that appeals to the next generation of leaders - the digital generation. 
Наука
Give an ancient man a stick and he will prove that the Earth is spherical. Give the modern man a computer and he will yell that the Earth is flat.
ASDF okay boomer
@@jackmasseywelsh337 ?
@@jackmasseywelsh337 you're one of those dummies?
@@whysoserious652 nah, I'm not saying the earth's flat, but ur a damn boomer
@@jackmasseywelsh337 boomer? srsly? you can come up with something new, dont you? dickhead..smh
Who was the man who walked in a straight line from Alexandria to Syene while counting every step? Now, that's achievement.
Why count steps? Let's make a wheel of a circumference of 1/50th of a Greek stadia attached to a stick with a handle, easy, then count the clicks or rotations.
D Watson odometer
D Watson You still have to count "clicks" or rotations in a distance of 800 kilometers. This wheel you are suggesting had to be big and terrain is unpredictable, you have mountains, desert, rivers etc... so, even with a wheel this is a challenge.
There is a smart way to measure that too. Measure how many meters you walk in a day normaly. Then count the days to go to the destination. Multiply, and you can come up with a rough answer. They must have been wrong 20%....but we have fixed it
They were actually very accurate.
The calculation was very impressive but so was the fact that someone could accurately measure a distance of 800 km by walking it.
I cant even accurately measure my bedroom just by walking and counting paces
They had the odometer for that.
Or he could walk at a constant speed of like 1m/s and count the time in his head during the journey and now that you have the speed and time passed you can find the distance traveled
@@78anurag Haha i hope you're being ironic
Well there were lots of disputes about land so they had professionals measuring distances. How exactly we may not know, but judging by how smart they were with distances we can assume they used some tricks as well. In order to make sure they're walking towards the right place they may send a guy to the horizon or as far as the eye can see towards Seyene direction. They'll have a cartwheel and on the wheel is a paint to count the rotations. Every time the paint comes on top you add 1. There'll be two guys at the start point and ending point to make sure you're walking in straight line. All they need to see is that you align with the other end. Of course they'll hold a big banner to be as visible as possible. The distance was 800km. Average person walks 5km/h. x 10 hours a day x 16 days = 800km. If it took 16 days more or less they could have done it numerous times from both ends to minimize the errors. They could have sent not one party but two or three parties from both ends at the same time and it would yield 6 different results within 16 days' time. See where each party reached and what their results were and you'll get a pretty accurate answer. Not to mention Eratosthenes was head of Library at Alexandria, working directly with the Pharaohs, tutoring their children, surely he had some of those slaves to work with.
Give a man a stick and he will prove to you the circumference and shape of the world. Give another man a stick and he will beat people up with it. It´s not the tools we have that makes a difference, it is the mind we possess.
meh, he got the idea from reading some shit in the library. One of your men could read, the other could not.
And let's not talk about what a girl would do with the stick.
Nemo7The7Pirate7 u idiot they didn’t have libraries back then
@@TheBeegestYosho The Library of Alexandria was around back then. It was arguably one of the greatest libaries of its time. Be careful of who you call an idiot.
Breakthroughs come when mind directs the tool rather than tool directing the mind.
Flat earthers : ''tHe EarTH iS FlaT''
Eratosthenis : Hold my stick
🤣🤣
"Actually... ...give me the stick back"
@vladimir putin is andrei panin jfk is jimmy carter I am a seaman you literally see the curve from the top of mast... If that is not enough you can see the ships start disappearing in the distance from bottom to the top due to the curve you can see it with the binoculars... and third our plotting course calculations and arrival at the designated point with theorems based on round earth are always correct....
flat Earth model is round as well so Eratosthenes found out how big this roundabout is, that's it.
You simply believe fabricated history, only believe your own eyes
Eratosthenes: The Earth is a globe. I calculated the Circumference.....with a stick.
15th century sailors: We see the ships' masts before their hull, therefore the earth has curvature.
Gustav Coriolis 16th Century: The earth is spherical. Cannon shots and missiles appear to deflect off target when fired Northwards or southwards because of the the Difference in tangential velocity between the equator and the poles.
20th Century Aviation: We need to aim a little off target, Because that french dude Coriolis knew what he was talking about.
NASA: The earth is a globe we have pictures!
Satellites: I EXIST
Flath Earthers: iT's A cOnSpIrAcy!! tHe eARth iS fLaT
Basically Flat Earthers in a nutshell
It is amazing how backward as a civilisation we have become. Yet we seem to look at people from the past as ‘dumb’ and ‘moronic’.
@@troygrindley3793 Because since 20+ years we have access to the internet. With a few clicks and in a fraction of a Second you can have all the stupidity you can imagine right on your screen. It's also so much simpler to group together other stupid folks.
First was Aryabhatta and Indian Astronomers
NASA: We have live feed of astronauts on spacewalk
This level of ingenuity from a man who lived so long ago is awe-inspiring. He figured out the earth's circumference from those simple facts? Mind-boggling.
You can do this in your room, on your flat floor. Put one stick above the ceiling light and one farther away. The stick just below the light cant cast a shadiw but the other one that is farther awat castted a shadow.
@@ayingchanda but the light rays will not be parallel anymore and the distance wont be to scale either
@@ayingchandayes, but could you figure it out on your own thousands of years ago with no prior knowledge like he did?
Why he has to go through so much trouble when 1,000 x 360 deg x 365.24 days in a year = 131,486,400 and divide it by 5,280 ft will give us the circumference in miles. So much easier isnt it?
you're aware that practically all geometry and a lot of math comes from them (and earlier ones that the greeks borrowed from)?
And just like that he payed a dude to walk 1600 km.
HAHAHAAAAA.... That cracked me up... I want that job...Low stress... Damn tech...
They had professionals doing just that. They walked at a steady pace and counted their steps. It was a job.
It just show us what a fery tale the story is 👆😂😂😂
No 800km
@@saul_goodman15 lol. Back and forth…
Funny how everyone is arguing about how but no one acknowledging how accurate he was.
TheMindskinner today meh, but for the era, just impressive
It's not meh, it's extraordinary.
@@user-po6hn9id1t Today is a meh? You do realize half, hell even half of the world population probably don't know about this.
@@user-po6hn9id1t Today meh? wich average person would come to this idea today ?
@@alamut8402 everyone would just be surprise about it for few seconds and go straight to their daily lives and do what they usually do. So yeah it's a meh
The ancient Greeks were way ahead of the curve on this. Get it?
your argument is rather circular.
Vikings knew Earth is flat and made of a giant.
Vikings were only so smart because they stood on the shoulders of giants..
OK. Chris W.
Babbling again, without even the faintest clue of basic math, physics and Scandinavian history?
Eyyyyyyy
This blows my mind completely. By no means I could figure this out but it seems so logical. Props to the GENT walking 800 kilometres too
It's not logical at all😅😅😅 only fools would believe this proves a globe.
This. This seems logical?
@@hir3d Yes . Yes it does?
@@michaelmacdonald880 It is logical, but you are right, this alone does not necessarily prove that the Earth is a sphere, just that there is a curve in the Earth between the two cities.
@@mitvulf this doesn't prove any curve...I can do the same experiment on a pool table with a flashlight and have different shadows 😉
Nice try
The story of Eratosthenes is one of my favorites.
My too…One of the favorites fairy tales 😂😂😂👆
The ancient Greek was really a great nation my great respect to them even 500 BC they are more advanced then some peoples 2000 AC who still believe in flat earth
Ahmed Malik You are referring to geniuses of ancient Greece.
As for present day “flat earthers” ,they either have delusions and need professional help or, more likely, they are insincere attention seekers.
They know that it is not easy to “prove” that the world is round. You know their gambit; do not even try to refer them to photographs taken from space probes.They will dismiss those as “fake”.When you get engrossed in “proving” that those photographs are “not fake” you end up forgetting about the original argument. It was about “proving” that the world is round ,NOT debating the merits of photographs.Moral is, it is difficult if not impossible, to “win” an argument against an insincere person.
all are idiots.
Earth is donut shaped !
flat earth?! pffff give me a break 😆
@@thandasibisi7534 i always wonder why a sincere flat earther doesn't just walk straight all the planet. He will come back to his initial point.
Or will he have an argument for that too ?
This made me redefine the meaning of genius
They used Kilometers 😍😍😍😍😍
YouCan'tAlwaysGet WhatYouWant idk why but I laughed at this.
Pineapple Cake yeah idk why it used “😍” emojis for...
He used Stadia not Km we converted it to Km
Honestly i'm American and other than measuring your height the Metric system seems much more useful. Like why the heck is a mile 5280 feet? A kilometre being 1000 meters is so much better.
@@chasington5102 haha the wiki on measurement is a TREAT !! look up Foot or Mile . Its like 200 pages long !! Shows just how completely fucked up We ( the US ) is as far as not being able to start the colonial US using the same base systems as the Ancient Egyptians did. This set of articles and "science" really cemented my utter disgust at the way humans did shit across the years. Not to Mention why they did it = Normally religion. I am now completely pantheist, and NOT a Flat Earther ! Although I completely think the Big Bang is bullshit too ! There is a photo meme out there that shows the galaxy - with a tiny pie slice saying ( what we actually know ) , a bit larger slice ( what we THINK we know ) , and the rest of the space ( like 90 % ) is listed as What We Don't know, that we Dont Know yet !
Rly great vid! We actually watched this for physics class, and it's easy to understand, and perfect for learning stuff real quick! Also, those Animations r very calming and fun to watch, they are a perfect addition to the explenation and well fitting! Pls keep on doing such great videos, they are really helpful!
Just a stick, his brain and someone willing to walk 800 kilometers counting every step. o.o
Odometer
ummm I think they don't have walked that distance specifically..I mean a wagon or a horse would have giving the same result quite accurately and efficiently
When life gives you a stick, you gotta calculate the Earth's circumference.
This is why I love you guys.
Excellent stuff☺️
Brooo, isn’t it insane though that through mathematics this man was able to find the circumference of the whole planet using shadows 🥴
if he lived in the time of Nostradamus , the ruling class would have burnt him at the stake for being a witch !!! ( why ? because he weighs more than a Duck !! )
Shadows were so important to mathematicians back then, that they formed a club called "League of Shadows"
@@309JJB U fr?
@@309JJB source?
This was explained to me decades ago by an amazingly interesting physics teacher, who wove stories like this into his lessons. I loved that class and looked forward to it every day because of a fantastic teacher. My mind was blown by the simple genius of this. Eratosthenes also gave us the longitudinal and latitudinal lines. He was apparently irascible near his end, from blindness, then starved himself to death.
How did he know it was exactly the same time though?
@@Jokl92the position of the sun in the sky. they used sun dials I think
Nice simple concise film,thank you.
Thanks for this informative video! Very helpful!
Best explanation. Thank you.
FYI guys, this experiment doesnt prove the Earth is round, but it does accurately calculate the Earths circumference if you first assume the Earth is round (which duh, it is).
Let's say you have two small sticks. You find flat ground and you stick one right below you and the other one two feet away. Then you shine a flashlight directly down at the stick below you, youll see it wont cast a shadow but the one two feet away will. You can't find the circumference of anything using the shadow because you're on flat ground.
But dont let anyone who believes the Earth is flat use this against you. The sun shines directly down on that city only once a year, so what does that tell you? That the Earth is at a tilt and this leads to more proof the Earth isnt a disk.
Ed, you have no idea what you are talking about. That is not how you do the experiment. In both places you wait until the sun reaches the highest point in the sky and look for a shadow. If you see no Shadow then the sun is directly above you. If not then you are in an area of the planet where the earth is beginning to curve so the sun will never be directly above you. (At least during that season because the planet is tilted because of the moon. If you ever travel to a place like Finland you will notice that the sun will barely make it across the Horizen and create a huge shadow because it's so far up the globe. The winter in Finland will have much shorter days then the winters in New York at the same time. Plus you have the 2months where the sun never makes it above the horizen at al, and 2 months in the summer when the sun never goes below the horizen and you always have sun. You have to visualize it 3-dimensionally with the earth tilted on it's axis.
Well, actually if you see it from a different perspective, it could be a disk where the sun located on top is moving from left to right passing above every single year
Best quick and concise video on the topic!
I love the way the video is structured. Thanks a lot uploaders.
And someone walking a few thousand steps...
Most people have a stride shorter than a full meter, so this would have required at least 800,000 steps (maybe he got a chariot ride on the way back).
Someone used sticks on a chain of known distance, and a couple of more sticks to make sure that he kept the chains in a straight line. (Surveyors have been doing this for a *long* time.)
Thank you BI ~ Eratosthenes used the Pythagorean Theorem, as do modern scientists, to do his calculations.
Incredible! Thanks you
Thank you so much for the explanation!
I've known about this ever since I was a kid, but the story impresses me anew each time I think of it. Beautiful minds.
During those Times when social media never existed, they weren't wasting time unlike us 🤷🏻♂️
Thank you bro 🙏🏻
That video change my mind omg
Great presentation. Thanks.
I'd like to give a shout out to the guy that walked and measured the distance between Alexandria and Syene
Give a shout out to the chap who invented the plumb bob so he could make sure his stick was perpendicular.
maybe there was a typo and he actually went to the Seine ( river in Paris ) . But they burnt the dude at the stake for being a Witch ! then Eratosthenes just guessed , so as not to look like an idiot !
and 2017 man believing flat earth
Great video, thank you
This animation and video was really helpful. Thanks for this awesome and helpful content💓💓
It's amazing the guy hired to measure 800km got it right and didn't cheat.
he went and got a beer & guessed :)
Plot twist: He guessed and just got lucky. To this day he is hailed a legend.
Pure genius.
This was actually the second time someone measured the circumference. The first attempt is described by Archimedes but he didn't give the name of the scientist that tried. It was based on astronomical observations (measuring the length of an arc). The third attempt was done by Posidonius, also measuring the length of an arc. Both Eratosthenes' method and Posidonius' are described in the extant book Circular Theory of Meteors by Cleomedes
Awesome. Absolutely awesome
If Eratosthenes used the greek foot 36/35 of the English and increased it to it's standard geographical length i.e. multiply by 1.01376, then multiply by 500 to get the stadium, this would fit the meridian circumference exactly 252000 times and therefore Eratosthenes is 100% correct.
Actually it was 5% off the current mesurement, but still pretty close !
Very nice and useful presemtation bro. Wel what software have you used in this video?
where can i find playlist of similar videos?
wiki ! just grab one and plug the name into YT !! ;)
That’s such a clever way to figure out both that the earth is round and the circumference! And kudos to the champ that paced out 800km.
But how did he know what time to record the shadow angle? Did they have their sundials in the area synced up?
They took measurements at solar noon at each location.
He probably directly measured the length of the shadow every few minutes as the sun approached the position directly overhead, then once the shadow started getting longer he stopped.
You can easily determine when noon happens using the gnomon, a vertical stick. Alexandria and Syene roughly lie on the same meridian (not exactly, there's an offset that doesn't really matter) therefore noon happens on the same time
How brilliant he was!!!😱😱😱😱
Nice Broo i like your video
Carl Sagan helped popularize Erathosthenes in COSMOS... I never met him personally but I do miss him a lot.
I must invent something universally great before I leave this world
..
Respected Sir / Madam
This video is very useful for teach Eratosthenes contribution in Geography. Please give permission to translate this video in Marathi (India Regional Language) to better understand concept in regional language. Please reply as soon as possible. Thanking you and oblige.
they'll never find this comment, contact them directly from their contact section on the channel or website
I wonder how many flat earthers has ignored this video? 😆
I'm happy he gave sources/credit to Carl Sagan :)
RESPECT TO THE GREEK MINDS.WE GIVE SO MANY AND ALL FORGET US NOW.
Not everyone has forgotten you. The EU and the Euro has destroyed a lot in your country, we must get rid of it.
the retardation
-a greek
You? He was man that lived 2 millennia ago. The greeks currently are nothing special. Stop boasting what some people did 2 millennia ago and start doing all those yourself.
This is meant to be an advice. No offence intended.
Fearofthemonster ughh, hater...
pazarimen2 Egyptian minds, all Greek philosophers have learned from the mystery schools
I think the one flaw is that the circumference he measured was north to south, but the earth isn't a perfect sphere. Had he also done the same experiment east/west he would've found a bigger circumfrence, but I'm sure that guy's feet were very tired
brilliant! :D
A stick, his brain, and a guy who counted every step between two cities.
And one flat earther dislike this video
+Aditya I'm not a flat earther, but obviously you didn't think this trough;-)
Imagine yourself in a room with a ceiling light. Put a stick right under the light, and you see no shadow. Put a stick a few yards from the other stick and you will see a shadow. Now be honest, does this prove the floor is curved?
They had no way of *proving* that the Earth was round; it wasn't as if they could leave it and have a view from a distance. However, this was an extraordinarily profound step in the demonstration of abstract human thought, one that is beyond many who exist today.
+Alex In my opinion there is no way a vew thousand years ago people could imagine a globe earth and a million miles sun millions of miles away, not even with the biggest abstract imagination and an IQ of 200.
The fact that we know these things from early childhood stops us from realizing how unimaginable the whole thing is.
Somehow, I just don't consider it too farfetched, considering their other mathematical achievements. However, anything's possible. For all we know, this is just a computer simulation and the history we're taught could be a complete fabrication.
+Alex Either there have been higher civilizations that are hidden/ignored, or as you say even weirder things could be going on.
I noticed you started explaining the experiment by saying, "IF the suns rays are coming in at the same angle at the same time of day". How did Erastothenes determine that the suns rays were parallel?
Eratosthenes had more knowledge in his brain, then all flattards combined, so he knew that the Sun must be very far away, since it doesn't change it's apparent size or speed during the day, no mater from what location you are observing it.
And, since the Sun is so far away, its light rays can only come to Earth almost parallel.
@@max5250 Circular Reasoning. You've yet to establish that the Sun is, "so far away". You're making the same leap of logic that Erastothenes made.
@@Jacois
Would you be so kind to explain how can a simple observation be "circular reasoning"?!
Have you ever observed a change in the size and speed of the Sun during the day?
We have already established that the Sun is "so far away" since it never changes its size or speed during the day.
He just assumed that the sun was so far away that the rays can be treated as parallel.
Awesome
What is the angle between stick and shadow?
Hi I actually did the measurement myself a couple of weeks ago using the data from planes :D and got pretty good results around .76% error. I did a video about it too :D
oh good is the earth a glob or not?
Can you link it?
Planes do not allow for curvature. Ask some pilots.
@josi gold why though? Would've done something more innovative.
Why he has to go through so much trouble when 1,000 x 360 deg x 365.24 days in a year = 131,486,400 and divide it by 5,280 ft will give us the circumference in miles. So much easier isnt it?
I'm just curious. How did they keep track of time? how did they know that during that moment, when the shadow casted by the stick angled 7.2 degrees was parallel to the time when the sun was direclty above that building in Syene?
wasol teron The shadow would be longest at sunrise and sunset, so the shortest measurement would be noon.
He did not need to measure both at the same time, there is always no shadow in Syene at noon of the summer solstice. To measure at Alexander he had to set up his pole correctly(plumbob and two right angle triangles) and at noon measure the shortest shadow on the summer solstice.
wasol teron Great question!
His Honer, Special Council Covfefe Chocker Smart answer. You must have been there with them as a time traveller to see the project through.
@@dwatson6785 thank you for that… That’s the best explanation that I’ve gotten so far… The shortest shadow… But it still doesn’t explain it to my satisfaction. Because if I’m an old guy walking around in a toga… Noon to me is when my straight stick which I hold vertically cast snow shadow. That’s Noon to me. On another video, the presenter said he looked up in the sky and saw the sun directly overhead, And so he called that noon. It’s just that that is the least scientific aspect of all of this. Because I can get a stick that straight, and I can use a plumbob to make sure that it’s vertical… But it just looks straight up in the sky and then tell myself yup that sun is directly over my head…… That’s not quantifiable. The sky is pretty big…
How did they measure the distance from the 2 cities? This is so crazy. I will never not believe that people were way smarter back then
How do you know if you are walking in a straight line over a long distance?
Use the sun at the day and some know star at the night as a reference point... It's not that hard if you just think about it.
Proves the power of mathematics and the human mind.
Actually, he did not tried to measure the exact circumference but to give an upper limit for it. He waited until the until noon, where the lowest angle could be observed. As Alexandria is farther west then Syene this had occured on a different point in time. Therefore, only the North/South distance should go into the calculation which is shorter than the actual distance. Unfortunately, he had no meas of checking how much the deviation is. Nowadays we know the error was 7.7%.
Nevertheless, that is a great achievement. I just think it is a really bad habit to say that he measured the circumference while he just measured an upper bound. This is a very important difference Eratosthenes knew about.
I don't think the video claimed that Eratosthenes was calculating the "exact" circumference. Even a "upper limit" is still a circumference measurement
@@vrisbrianm4720 No, he was calculating the exact circumference. It says so in the video. I think you are confusing circumference with the exact area of an entire sphere. The Circumference is the 2-dimensional distance around the middle of a ball.
No, he was attempting to measure the exact circumference. Aristotle already knew it was round. 7.7% is not the error. it's the calculated distance of 7.7% of the pie. HOw on earth would he have the exact calculations of the cirumference of the Earth if he wasn't looking for it. That makes no sense what so ever. Whatch the video and Read about more carefully. do the math.
@@309JJB I don't think I am the one who was confused. Eratosthenes was trying to calculate the circumference based on available data in his time. Whether the actual value is "exact" or not is not relevant. That's why I think @PFYannik was overthinking it.
amazing
Back in the days erathosthene not only that earth is round but also calculated the circumference just using 2 sticks
Fun fact the distance between the Sun and Earth was accurately measured centuries before modern science in one of the Hindu books
i guess they knew basic math too
what does this have to do with hinduism
@@Haris1 you can google the same: i just pasted it.
Hanuman Chalisa’ Precisely Calculates The Distance Between Earth And Sun
“Yug sahasra yojana par bhanu,
leelyo taahi madhura phal jaanu”
The above excerpt is from the Hanuman Chalisa and translates to: ‘[When] Hanuman travelled thousands of kilometers to swallow it thinking of it as a fruit’. The word-to-word translation of the same excerpt reveals the distance that Hanuman travelled.
1 Yuga = 12000 years. 1 Sahsra Yuga = 12000000 years. Also, 1 Yojan = 8 miles.
Hence, “Yug Sahsra Yojana”, the first 3 words mean 12000*12000000*8 = 96000000 miles or 153,600,000 kilometers. Interestingly, the actual distance from earth to sun is 152,000,000 kms. Bafflingly, there’s error of just around 1%
And there are still people that believe the Earth is flat...Eratosthenes is rolling in his grave
Rotting not rolling. Oh wait hes a bag of ash already lol
He's up there with Sam Kinison and Dio and Jesus smokin stoggies and drinkin good whiskey, playin poker and betting on what kinda dumb shit we will come up with next !!
What an absolute genius.
One thing not explained is : how "the man hired to measure the distance..." did it. It was a profession at the time to measure distances by walking and counting the steps. It is easy for one kilometer. But 800km in a straight line? Easier said than done.
I saw one video where he was supposedly off by about 40 kilometers. That’s one of the main reasons Eratosthenes’ calculations were off by a little.
By that time, the Earth was not flat. But thanks to our Government conspiracy, they secretly turned it flat about 60 years ago and kept it a secret. This must be the biggest prank ever :D
People in 2018: the earth is flat
He's a legend
The song I’m Gonna Be by The Proclaimers is about the man Eratosthenes hired.
“And I would walk 500 miles (~800 kilometers)
And I would roll 500 more
and just like that some modern men with all the knowledge of the whole internet decided that the earth was flat. flat earthers need to go
for sure Kyrie Irving disliked this vid
Marvin Elaurza HAHAHAHAHAHAHAHAHA YOU MADE MY DAY
Lol
and 2,000+ years later flat-earthers even with all of our technology still don't understand that, it's wonderful
with just a stick and his brain...... and that poor man who paced around for approximately 800km who probably started back again if he lost count... we probably need to give him credit too XD
QUESTIOOONNNN!!!!! How did they KNOW when NOON was????
Ummm... That seems verrrry unique to Season and Latitude and Location obviously... The sun is NEVER directly above your head. May be over your head but directly over is as rare as an eclipse happening in that same spot too ATLEAST
when the shadow is the shortest.
Yes, when the shadow is shortest.
How could he determine that the shadows of those two sticks were inspected at the same time?
He only knew where the same (one) subsolar point location was one year later. His timing however for recording the angle of the stick shadow at the exact moment of subsolar transit 814 km away is on another level of impossible to imagine without a modern time piece and communication. Using an online subsolar calculator and three shadow markers over the course of one day my 'centre of the earth' result varied by more than 1000 km. I fail to see how just one data point lead an ancient to assume anything when data from another two or three shadow locals would have thrown his result to absolute chance. rl.se/sub-solar-point (plus) www.omnicalculator.com/math/right-triangle-side-angle plus G maps.
May be
He took the measurement over two years.
First year , on zero shadow day in syne, he took series of measurement of height of shadows. Lets say if he took 100 measurement of shadow from sunrise to sunset. In that series he will find one measurement with zero height of shadow. Lets call that time Noon.
Next year, on zero shadow day in alexzendria, he might went and again took 100 measurement of the height of shadow. There he will not have Zero height of shadow but will have the shortest shadow. In the series ,he will have the shortest height of the shadow. The time in which the stick cast shortest shadow is noon for that place.
The time in which he took zero measurement in syne and shortest reading in Alexzandria could be considered simultaneous.
Thus he was able to calculate earth curvature passing through the line from syne and alexzandria.
@@sagarthapa7394 'May be' the shadows in you living room point back to the ceiling light, why would that one simple observation lead you to believe your floor is now concave.
@@sagarthapa7394 sounds logical as long as the earth keeps her rotating speed :) thanks :D
Brilliant
did he take into account the direction in which the other city was located? If not then he was lucky they were separated by a line almost parallel to north-south
He thought he was due north but was slightly off.
The man that walked 800 km deserves a name!
he probably used a boat but yeah, i am sure it wasn't the best trip he made
This is why I love men so much. They have brains and sticks. There is not much more to ask for.
Linda Kloss bish what?
Thank you, we try to do our best at whatever we do.
we need more women like you Linda
What type of clock did he use to make sure he measured it from both locations at the same time ?
31 dec 2022 9:29 pm est(utc-5) : 0:50 : that 7.2 degree angle , create shadow-length which is shortest-shadow-length of that-day/summer-solstice-day , shortest-shadow-length of a day , produce meaning 'current-time is mid-day/noon' . 0:36 : in syene : shortest-shadow-length of summer-solstice-day , is no-shadow .
31 dec 2022 10:10 pm est(utc-5) : i make mistake , you're correct , eratostenes lack clock which make sure shadow-length-measurement happen at same time ( concurrent ) . so shadow-length-measurement maybe happen in different moment , which means syene/aswan is not in-1-vertical-line-with alexandria , which get confirmation from current map which show aswan is not in-1-vertical-line-with alexandria .
but maybe eratostenes try walking-and-following compass-north starting on syene/aswan then eventually arrive in alexandria then eratostenes thought alexandria is in-1-vertical-line-with syene/aswan . so maybe modern map is not accurate ? and eratostenes with compass is more accurate .
31 dec 2022 10:22 pm est(utc-5) : wiki/Eratosthenes says syene-city change-name to aswan-city .
1 jan 2023 4:45 am est(utc-5) :
maybe gps-satellite know north-location via beacon-signal from gps-ground-station in sweden-country->kiruna-city .
source :
sscspace[d]com/services/satellite-ground-stations/our-stations/esrange-space-center-station/
from google ( north pole ground station for gps ) result 3
maybe kiruna-city is not accurate-representation of geographic-north .
geographic-north is 1,000 mile away from magnetic-north .
[source : '1,000' in wikipedia[d]org/wiki/Compass ]
if geographic-north is not accurate then google-map is not accurate .
Solar noon is the time when the sun is highest in the sky.
They took measurements at Solar noon at each location.
@@A_J502
It didn't matter if these measurements were done _years_ apart as long as both were done at noon on the summer solstice.
One source of uncertainty is that Syene isn't due south of Alexandria, but somewhat further east, making the distance between them slightly longer than between their respective latitudes - in addition to the challenge of measuring that distance precisely with the methods available.
It's crazy that all you need is geometry to do this.
Ancient Greek is F**king GENIUS!!!!
Interesting !
But how was Erasthosthenes coming to his conclusions without taking the refraction and light bending of the earths athmosphere into account ?
The refractive index seems quite low, but without even mentioning it and without taking this into account it seems questionable whether his results are legit.
How in the world would he think the sunlight would come in as parallel rays when he observes crepuscular rays ? And what about observing the size of the sun compared to the size to the moon (at that time) ?
It seems also questionable that they were able to measure the distance between this places to that exact amount. Taking this room for error into account seems even more questionable regarding his kinda exact results.
If i measure the shadows on a table from the same two obects at different locations under the light of a lightsource above a bending medium like a lens while the source of the light is not visible for the imaginary observer standing on that table but only the light coming through the lens, the observer can come up with a mathematical formular for spherical geometry of that table he is standing on, and is able to make predictions based on that model. This might be the conclusion whatever, when not taking the refraction of that lens into account. Furthermore, based on this mathematical model, it will be possible to make predictions and equations to describe the convexity of the surface of for example standing water over a certain distance, because, based on spherical trigonometry and geometry, all standing water will have to follow the geopotential surface of the geometric "body" its on, in this case the earth. However, all standing water is always level and predicted convextiy can NEVER be measured or detected. How does this come ?
How is it possible, that Eratosthenes didnt know that and that he didnt take that into account - According to his model there should be a physical horizon given for any observer based on spherical geometry. How comes an observer can make precise predictions based on this eqation for the earths curvature and is never able to observe any of that and is in fact able to see distances with his naked eye which would be physically impossible based on this spherical geometry ? Do you see the point ? Whats the surface of that table ? The result of my math equation ?
When does history make the first recorded statement about Eratosthenes and this experiment ? Why is no source mentioned here ? I didnt find any older mentioning of Eratosthenes than 1902.
Please help me with this questions. :)
It just shows a fairy tale was created to fool people about the globe. So many questions about this "experiment" ...
:) thats because the religious folks burned it all when they burned the Library at Alexandria . Got to remember , this ( 2020 ) is not the first time the Earth has " been flat " according to the "leaders" :) Maybe we will start burning people at the stake again shortly !! OH the Unvaxed !! BURN them !! They Weigh more than a DUCK !! haha
1:25 How do you pass the stick and the shadow making a 7.2º to the two cities making a 7.2º?
@thetlwalleri mean how do we reach the conclusion that the cities are 7.2 degrees apart just by knowing the angles that the light makes when hitting the sticks. And you are wrong, you can't have a perpendicular angle.
A nice tale however, a physically impossible test to perform to any close degree of accuracy. Way too many variables involved and, at the time, inaccurate assumptions of the factors used.
Oh please, enlighten us.
@@Cannibal666Corpse still waiting
Erastosthenes did not proved that earth war round , he believed so because he studied Aristotle , but the same effect happens if the earth was flat and sun was much closer and smaller than the earth . And he could not tell that in 200 BC.
so funny all these people who still think the Earth is a globe...HA! they have no clue to their indoctrination
some guy says oh that is also possible on a flat earth and you believe it instantly
no this cannot happen if the earth was flat and the sun much closer
did you even watch the video???
We all know the earth is a sphere (nearly perfect) however I kind of see what you mean. If the sun produced rays at all angles being directly below the centre of the sun would produce no shadow while if you where at the fringe some rays would come in at an angle from the side producing a faint shadow.
Oh and it was already known but not mathematically proved that the earth was a sphere at the time of Aristotle because of observations like the new constellations being seen in different places in the world and the shadow of earth on the moon being rounded.
Gameplay Max Rez If the Earth is flat and the sun close then it would be extremely easy to measure how far away the sun is, in fact, Erastosthenes's measurements would have given a distance of 4155 miles for sun over a flat earth. With this, another measurement at 6300 miles away from the first on a *FLAT* earth would give an angle of 33.4 degrees, but on our Earth, we cannot see the sun the angle is - 2. So no the same effect doesn't happen. Do you want to know how to measure distances to the moon and the sun?
i have no words
he found the exact circumfrance (30 kms on 40,000 kms is negligible for the times and his equipment available to him). Here's to men of science, whatever ERA they come from. (*hug your sci teacher :)
The history is very educational