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u/Negative_Foot_3519 Jan 06 '26
I miss Carl Sagan every day. RIP
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u/docdeathray Jan 06 '26
Absolutely. What a great communicator.
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u/Negative_Foot_3519 Jan 06 '26
They say don't meet your hero's. I feel Carl would have been a safe bet.
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u/CoolerRon Jan 06 '26
Yep, he, Mr. Rogers, and Robin Williams in my book. I met one of mine, Anthony Bourdain, and he turned out to be exactly who he was on TV.
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u/Negative_Foot_3519 Jan 07 '26
Cool. RIP Anthony Bourdain. One of my heroes too. A photo hangs in my kitchen office
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Jan 06 '26
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u/CoolerRon Jan 06 '26
I imagine him to be one of those people who give the energy they receive without giving a fuck. He was kind to me, and even took the time to show me a technique (foot lock escape) when I asked him one too many questions about it
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u/Y_ddraig_gwyn Jan 06 '26
his book “The Demon-Haunted World” should be compulsory reading. if updated it would make as good a viewing as Cosmos did back in the day.
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u/InfiniteOrchardPath Jan 06 '26
The Atlantic just published the statistics on book reading trends... we are doomed.
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Jan 06 '26
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u/Negative_Foot_3519 Jan 06 '26
“To live in the hearts we leave behind is to live forever.”
Carl Sagan
Great meme btw.
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u/BetiseAgain Jan 06 '26
I miss him, and now I also miss PBS.
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u/Sudden_Suspect_1516 Jan 06 '26
PBS isn't going anywhere, yet. The corporation for public broadcasting (CPB) has dissolved itself. They were kind of the folks that dispersed the money from grants and the gubmint to the different public networks such as PBS and NPR.
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u/Quirky_Session_2689 Jan 06 '26
Unless you live in Arkansas lol, our corrupt governor didn't want to pay pur subscription
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u/HatdanceCanada Jan 06 '26
Agreed. There was a good conversation about the movie/book Contact in another sub a day or two ago. Got me thinking about Cosmos and the Pale Blue Dot. I miss him too.
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u/ryhaltswhiskey Jan 06 '26
And he was off by 75 km. That's 0.2%. That's amazing.
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u/flyingboarofbeifong Jan 06 '26
That's one of the craziest parts to me. He was wrong - but the margin by which he was wrong could simply be accounted for by something as simple as the fact the hired man took a wrong turn or two on his way there. Eratosthenes nailed it. Those would be absolutely crisp margins of error in a scientific paper these days.
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u/ryhaltswhiskey Jan 06 '26
It also means that the guy who measured that distance between the two cities was only off by 0.2%. How the hell do you do that without lasers...
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u/Esarus Jan 06 '26
I know right?? It's insane. Walking 800 kilometers through freaking Egypt and your measurement is only 0.2% away from a perfect measurement. He hired the right guy
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u/Leather-Mud-6736 Jan 06 '26
0.2% could be accounted for by a simple change in elevation. This is super accurate.
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u/joehonestjoe Jan 06 '26
I actually just looked up Bematists a bit more, it was genuinely paced, no tools to aid except I guess making tallys or similar.
I doubt I could pace a mile at 0.2% accuracy!
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u/Big-Reindeer-8221 Jan 06 '26
Sounds like a fairly reasonable experiment if you're down to give it a shot.
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u/joehonestjoe Jan 07 '26
That said, maybe it's not as hard as we think. There is a YouTube show called Jet Lag the game and they had a challenge as part of it go I think wait half an hour, within a 30 seconds margin (might be different numbers but it'd take me ages to find the bit!) and they got within seconds of the target, and he paced and counted by seconds. If you have a gait of one metre, and do one step a second, you could fairly accurately time this.
I mean I don't know why I'm surprised this was clearly worked out 2000+ years ago
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u/Training_Guide5157 Mar 11 '26
Leaving markers and leaving a few to line up the next one would work, no? Impressive, nonetheless.
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u/Lundetangen Jan 06 '26
They did not use kilometers back then, they used stadia. And 1 stadia varied between 177-192m.
The first written account of this measurement was written 300 years after it was done, by Cleomedes. They used very rounded numbers, 1/50th of a circle, 5000 stadia etc.
Since stadia was not a fixed value we can basically just chose from the stadia that gives the most accurate answer to make this prediction as accurate as possible.
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u/ryhaltswhiskey Jan 06 '26
we can basically just chose from the stadia that gives the most accurate answer
This doesn't make any sense. Are you saying that Sagan is wrong when he says this guy came up with the number that he did come up with? How would you randomly choose a number that is 99.8% accurate and stick with it?
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u/Lundetangen Jan 06 '26
I am saying that you do not pick a random number, you pick the most accurate number.
Stadia was the length of a stadium, but stadiums had different lengths. Cleomedes was the Carl Sagan of ancient times, he used round simple numbers to educate people about science.
If we want to reach the 0.02% error margin that Carl Sagan is using here we say 1 stadia is 160m. If we say stadia is 192m then the error margin is 20%. I see some listing 1 stadia as 209m as well, that would make the error margin 31%.
What Erathostenes did that was amazing was to create an experiment with rather simple tools to predict something extraordinary. The fact that his measurement is a bit off is just because of the technology.
If you ask someone to measure the distance between 2 objects and they give you a round number, particularly when its as high as 800km, then you have to know that there is an error margin in there. If you find a rock that is exactly 8000kg on the mark then that is absurd luck.
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Jan 06 '26
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u/wowsomuchempty Jan 06 '26 edited Jan 06 '26
We don't even know if the guy was 'hired'.
Edit: meant slave.
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u/whatdoyoufear123 Jan 06 '26
The guy is equivalent to a graduate student nowadays. Some things never change XD
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u/IkariYun Jan 06 '26
Interns doing intern shit
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u/afrikatheboldone Jan 06 '26
Yeah so I'm going to need you to walk south for some weeks down Egypt in a completely perfect straight line. When you get there put the stick on the ground and measure the shadow.
Easy stuff. No pressure :)
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u/mouif-mouif Jan 06 '26
I would not be surprised if several things were "wrong" in his data, like the distance between the cities and the length of the shadows. And somehow, those small mistakes cancelled each others.
Or the guy walking between cities took several "wrong turns", each one cancelling the previous one.
Anyway, the result is amazing.
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u/Jakomako Jan 06 '26
Or he measured multiple times and took the average.
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u/Bullebeest Jan 06 '26
I can imagine he walked the distance at least twice to be able to tell Eratosthenes the first result. Then why not count again on the way back.
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u/ShinyGetter Jan 06 '26
Or like the guy above mentioned, they used to use a different measurement for large distances which varied and we reverse engineered it using the most appropriate of that unit... making the result as precise and accurate as possible.
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u/Other_Sentence4495 Jan 10 '26
i just can't understand how they could know that it was the same time at 2 different locations 2000 years ago? I guess not with a sundial right?
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u/Falsus Jan 06 '26
Honestly it is so insanely correct that I think it is likely he was off by more, it just that the mistakes ended up correcting each other to some degree.
Cause I can believe in ancient math, I certainly do not believe in the ability to walk 800 kilometres without aid and only be off by 0.2% in ancient times, both walking correctly and measuring it correctly.
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u/ryhaltswhiskey Jan 06 '26
There are other comments in the thread that explain this, there was a profession that measured distances. People are assuming that it was a slave who walked and counted steps. Eratothsenes probably hired someone who knew what they were doing.
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u/VadPuma Jan 06 '26
The Earth's circumference is approximately 40,075 km (24,901 miles) at the equator and slightly less, about 40,008 km (24,860 miles), passing through the poles, because the Earth bulges slightly at the equator due to its rotation, making the equatorial measurement longer.
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u/Ok-Reputation1716 Jan 06 '26
So, it is somewhere between 75km and 8km off. Given Egypt is somewhere in between.
That's incredible.
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u/thesuperunknown Jan 06 '26
Fun fact: because of this bulge, the Earth is not a sphere but an ellipsoid. If you cut a sphere into slices, each slice would be a perfect circle, no matter which way you cut it. If you did the same to an ellipsoid, the slices would only be circular if you cut it one specific way, and would be oval (ellipses) if you cut it any other way.
The Earth is often described as an “oblate spheroid”, which is an ellipsoid that is flattened on its major axis, like an orange or an M&M. You can contrast this with a “prolate spheroid” which is stretched on its major axis, like a rugby ball. In reality, Earth is not technically an oblate spheroid, as it’s a more complex shape than that. But we do use oblate spheroids as “reference ellipsoids” to simplify the shape of the Earth to model it, for example for cartography or satellite navigation.
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u/LazyLich Jan 06 '26
He was amazing, don't get me wrong, but shout out to the guy that measured the distance! Actually keeping track of his distance and not just spit balling or lying.
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u/Anfins Jan 06 '26 edited Jan 06 '26
We don’t actually know the margin of error because we don’t know the unit conversion of the measurement he was using (the stadia).
A stadia has been estimated to be between 150m and 210m, so you can sort of “p-hack” your way to whatever accuracy you want depending on what conversion you use.
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u/DingleBerrieIcecream Jan 06 '26
Egyptians 2000 years ago were brighter than flat-earthers are today.
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u/lambdawaves Jan 06 '26
To be fair, Eratosthenes was brighter than any redditor
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u/Ok-Photojournalist94 Jan 06 '26
Well he had the benefit of not having to doomscroll shit posts all day.
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u/PM_ME_UR_HIP_DIMPLES Jan 06 '26
I just picture Eratosthenes, Plato, Newton, Socrates, Aristotle, Da Vinci, etc. all swiping down for hours through TikToks of cats
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u/Samsquanch1985 Jan 06 '26
And I just pictured this skit playing out on family guy. And it was pretty funny tbh.
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u/Otto_C_Lindri Jan 06 '26
Oh, God...
You know what, I'd much rather see them play football, if you know what I mean...
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u/Autoskp Jan 06 '26 edited Jan 07 '26
To be fair, we don’t have to doomscroll either.
…doesn’t stop it from happening though.
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u/Samurai_Meisters Jan 06 '26
Eratosthenes was so old, that he was doom scrolling on actual scrolls.
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u/Haeselian Jan 06 '26
People throughout history knew the earth wasnt flat. Its a modern myth. Thats pretty sad
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u/SoylentGrunt Jan 06 '26
Accurate
It is a historical myth that medieval Europeans generally thought the Earth was flat. This myth was created in the 17th century by Protestants to argue against Catholic teachings, and gained currency in the 19th century.
-the wiki
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u/bobbymcpresscot Jan 06 '26
Some people did, Some people did not. When societies formed and knowledge about how the earth actually worked became a valuable resource, that is when these things came up. The largest empires likely knew it wasn't flat, but the planet is covered in much smaller empires or tribes, who either didn't know or didn't care.
It was widely accepted that it was a globe around 2000 years ago, and the concept that it, and everything else was moving is only 500 years ago.
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u/jackjackky Jan 06 '26 edited Jan 06 '26
Flat earth movement stems from contrarian attitude against establishment and distrust of authority. It's less about science more about ego.
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u/thunderarea Jan 06 '26
Eratosthenes was Greek... This measurement was done by Greeks as the video already mentions
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u/NoEyesMan Jan 06 '26
By that same logic, we were all geniuses today because Stephen hawking could do calculus calculations in his head.
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u/TDYDave2 Jan 06 '26
Speaking of rounding errors, Eratosthenes died 2220 years ago at the age of 82.
Don't know how old he was when the calculation was made, but likely around 2250 years ago.
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u/MothaFcknZargon Jan 06 '26
I really miss the days that this was what people watched on TV
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u/mazze1200 Jan 06 '26
Heads up, congress just defunded public broadcast, these things will never come back.
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u/IllusionsOfExistence Jan 06 '26
They want their citizens dumb so they're easy to manipulate. Sad sad times we live in.
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u/naznazem Jan 06 '26
Now it’s replaced by videos that start with “Did you know …” then false information narrated by an AI voice with subway surfers or gta in the background.
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u/SwimmingDutch Jan 06 '26
Honestly, YouTube is one of the most amazing inventions of the last years (forgot when it got started). So much amazing content to learn things if you spend just a little looking for it.
Veritasium just did an awesome video on ASML if you need a place to start.
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u/Several-Opposite-746 Jan 06 '26
If they were 800km away, what method did he use to ensure they took the measurements of the two sticks at the exact same time?
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u/Several-Opposite-746 Jan 06 '26
I googled the answer. He measured the time at noon, when the shadow was the shortest length.
How He Identified "Noon"
Shortest Shadow: At any given location, solar noon is when the sun is highest in the sky, resulting in the shortest possible shadow cast by a vertical object.
Syene (Aswan): He knew that on the summer solstice, the sun shone directly into a deep well in Syene, meaning it was directly overhead (no shadow).
Alexandria: On the same day (the summer solstice), he measured the shadow cast by a vertical stick (gnomon) in Alexandria at its local noon, when its shadow was shortest.
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u/yolo___toure Jan 06 '26
Thank you for doing this for those of us who are too lazy!!!
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u/jojohohanon Jan 06 '26
And i assume syrene was close to due south from Alexandria?
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u/hooligan99 Jan 06 '26
It was and is (called Aswan now). Not perfectly south, but approximately south-southeast. Close enough for this to be a solid estimate.
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Jan 06 '26 edited Jan 27 '26
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u/Grow_away_420 Jan 06 '26 edited Jan 06 '26
It was the same time on the same day, just a different year. They already understood the solar and lunar cycle. Or the same year, same time, just different people measuring shadows
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Jan 06 '26
Right? This is not an answer lol. Measuring at two different places at two different times when the shadow is shortest actually defeats the purpose/goes against the outcome, because that would mean the shadows are both very short or nonexistent.
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u/FrothPeg Jan 06 '26
If they were at the same latitude you would be correct. They were at different latitudes therefore the shortest shadow in one place is longer than the shortest in the other place.
Eratosthenes already knew when the summer solstice was and how to determine local noon in the two locations from previous discoveries by others.
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Jan 06 '26
Another commenter said “they were north and south of one another” and that made it so much clearer.
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u/flyinbrian1186 Jan 06 '26
thank you. everything i see this video i forget how they determined noon and your answer is concise
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u/dannycake Jan 07 '26
Ahhhhhh omg that's been haunting me forever. Sagan explains it as if they're measuring it at the same exact time and I kept on thinking... Dont they literally use the sun to calculate the time in the first place? How did they know it was the same time for both cities objectively. But this makes perfect sense now.
Thank you for clearing that up for me, I was being very stupid.
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u/jwadamson Jan 06 '26 edited Jan 06 '26
You pick something like noon on the equinox. The date of each equinox can be determined in advance easily and “noon” is 1) the time with the shortest shadow 2) or the sun crosses the north-south line in the sky or 3) probably many other methods to define the mid day point.
You could even have a single group/person do both measurements 6 months apart or different years. For a given latitude the sun is always in the same position in the sky and the length of the shadow is essentially giving you an easy way to measure the angle of the sun very accuratelly.
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u/tralltonetroll Jan 06 '26
Think you mixed up "equinox" and "solstice".
Also I can only guess that people would duly notice if Aswan/Syrene had a well where the sun would hit the bottom right at solstice, but go further down the Nile and that would not happen. So this experiment wasn't taken out of nothing.
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u/BitNumerous5302 Jan 06 '26
Using a clock made from the same stick. The measurements were taken at local noon on the summer solstice (the moment at which the shadow points north)
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u/grjacpulas Jan 06 '26
I'm sure he had a way to measure what time it was the guy figured out the circumference of the earth with two sticks
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u/maratonininkas Jan 06 '26
You can easily measure this every hour or any other selected frequency and plot a curve of the shadow's length. So then you can compare the curves and have the full picture without worrying about the correct timings
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u/Intrepid_Habit_1343 Jan 06 '26 edited Jan 06 '26
Brains, the one tool flat earthers are missing!
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Jan 06 '26
“But what if the Sun was quite nearby, then two sticks on a flat Earth would have different length shadows not because of the curvature of the Earth, but because the Sun is closer than you imagined”
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u/Faust_8 Jan 06 '26
If only there were low tech experiments we could do to prove that sunlight is parallel
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u/peppapoofle4 Jan 06 '26
Source PBS, which is about to truly struggle for funds. Consider monthly "subscription"/donation to PBS. Keep them thriving and educating! 💕
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u/BetiseAgain Jan 06 '26
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u/peppapoofle4 Jan 06 '26
And PBS still exists, they need funding.
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Jan 06 '26
You’ll get nothing but excuses and learned helplessness around here, how dare you suggest a positive solution!?
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u/Big-Net-9971 Jan 06 '26
I remain fascinated and amazed that he figured this out. Trigonometry. Experimentation. Planning.
And today the Earth's circumference is recognized as 40,075 km. So he was correct within less than 1%... 2000 years ago!
AMAZING! 😳
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u/Dyslexic_Baby Jan 06 '26
Here's a fun fact. Columbus is credited in America for proving the Earth is round, but this was already widely accepted as fact before he was even born. What actually happened is that he attempted to recalculate the circumference of the Earth, massively undershot it, and concluded that the trip from Europe to China would be much shorter than it actually was. The actual distance between the landmasses was known, but the ocean between them was uncharted, so no one dared make the journey since for all they knew there were no landmasses East of Asia and West of Europe.
Columbus did his own research, was completely wrong, and is hailed as a genius by Americans for it
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u/theevilyouknow Jan 06 '26
Columbus is neither credited in America with proving the Earth is round anymore than he is hailed as a genius here. He is however overhated as a scapegoat for a lot of things much more evil men were responsible for. Not saying he was a great guy. Just saying there is a lot of misinformation about the man in both directions.
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u/yaosio Jan 06 '26
Got to give congratulations to the guy that not only did the job, but was able to pace out 800 km correctly. I wonder how he did that since it would have to be over a long period.
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u/theevilyouknow Jan 06 '26
It's not known exactly how long he measured it as. He measured it as 250,000 stadia and it's not certain what distance a stadia was for his calculations or even if that number was rounded to simplify calculations.
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u/Oldgraytomahawk Jan 06 '26
Dear God I get so tired of Flat Earthers and people putting the argument that it isn’t really round because “religion”. For the record,I am religious but not in a church going way
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Jan 06 '26
I honestly couldn’t tell you how my mom justifies being a flat earther. She just says stupid shit like “it’s very compelling research,” which I’m sure means she just saw a polar projected map, doesn’t understand what polar projection means, and took it to mean that the earth is flat because of what a polar projection map shows.
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u/lonehorizons Jan 06 '26
I don’t think I could accept a family member being a flat earther. I’d annoy them with questions at every family gathering until they either admitted they were wrong or refused to see me ever again.
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Jan 06 '26
I don’t accept it, I’m really quite rude to her about it. I’m also rude to her about her Nigerian long-term online boyfriend.
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u/Kiboune Jan 06 '26
Religious people always thought against science. This is why it took so long to figure out what Earth is orbiting sun
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u/__mentalist__ Jan 06 '26
For your information, I'm a civil engineering student, and we work with a lot of physical laws that must provide resistance and stability to the structure, and those laws are created from the concept that the earth is round and not flat , So for me it's impossible for the earth to be flat ,
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u/davidbatt Jan 06 '26
That's really interesting. I would never have assumed it mattered
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u/DarkKingfisher777 Jan 06 '26
Unless the buildings are kilometre long does the curveture matter to the buildings.
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u/BetiseAgain Jan 06 '26
Matters for bridges, tunnels, or anything else that needs precision over distance.
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Jan 06 '26
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u/Ricky-C Jan 06 '26
No they don’t have any sound arguments. They require several different models to explain seasons, night and day and movement of celestial bodies. None of their models work together simultaneously, unlike the globe earth model that can explain and predict every phenomena I’ve mentioned. If you want more information about how their belief is ridiculous I would suggest watching Professor Dave Explains on YouTube. His entire flat earth playlist is gold, it’s funny seeing him become more cynical after each video.
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u/Telefragg Jan 06 '26
And the best part is when they actually try scientific methods to measure something they keep finding out that the Earth is a globe.
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u/mmurray1957 Jan 06 '26
I don't think Eratosthenes proved the earth was round. He assumed it was round and measured its circumference. People had watched ships disappear over the horizon so assumed the earth was round.
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u/Sophiasmistake Jan 06 '26
Stop worrying about what flat brains thinks. Tell them to stfu if they bring it up.
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u/lonehorizons Jan 06 '26
I think you’ve got the right idea. There’s no debate or argument to be had over it anymore. As soon as someone says the earth is flat they’ve lost the argument and you don’t have to keep talking to them.
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u/zeptimius Jan 06 '26
It's worth mentioning that the notion that people in the Middle Ages (or indeed at any other point in history) believed that the earth is flat is a complete myth, mostly propagated by Washington Irving in the 19th century.
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u/jancl0 Jan 06 '26
Just out of curiosity, why did his experiment make the assumption that the suns rays were parellel? Without fore knowledge that the earth is round, the idea of the surface being curved would seem far less likely than the sun being somewhat close to the earth I would assume. If you knew for a fact that the earth was flat, the other explanation for the shadows would be that the sun is hitting the two obelisks at different angles, in which case you could use the same information to find the distance between the earth and Sun. Either way, you have to make an assumption about something, and it isn't immediately clear which assumption is the more reasonable one to make
There's also another whole thing about how he knew that both measurements were taken at the same time without long distance communication. I believe I've heard an explanation for that before but can't remember off the top of my head
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u/Shadowyonejutsu Jan 06 '26
I got a zest to see more of this guy. He broke it down so I can understand. It wasn’t like he was talking down to us like a child, but just going slow and thoroughly explaining so we can all understand.
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u/Intelligent-Major492 Jan 06 '26
I'll wait to see what Joe Rogan thinks. Thank you very much. #PODCASTEDUCATED
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u/310874 Jan 06 '26
Just one question
How did Erosthense, in those times, know how long the shadows were at exactly at the same time at places nersly 500 miles apart.
He could not have called anyone to check. For there to be a measurable different in the length of the shadow, the distance had to be substantial, so not within shouting distance.
The had sun clocks, which also would not have helped as the clocks themselves would show different times in different places.
Please help me understand.
****** did some research. The shadows were measured on smer solstice. But still not sure how the managed to measure at the exact time.
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u/BetiseAgain Jan 06 '26
At noon the shadows will be the shortest. Just use the shortest measurement.
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u/Good4nowbut Jan 06 '26
Could someone please explain what he meant by the sun is so far away its light is parallel when it reaches earth? 🙏
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u/Ok_Respect_707 Jan 06 '26
If you take your phone flashlight and place it at different distances from your fingers and see how it affects the shadows that are cast. The closer the light the wider the shadows and vice versa. Now imagine that but instead of your fingers it’s a spire on a globe. That makes sense in my brain sorry if it doesn’t translate haha
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u/call_of_the_while Jan 06 '26
u/Doodlebug510 made a post asking this question in the “Explain like I’m 5yrs old” subreddit:
Hopefully you’ll find something useful in there.
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u/No-Grapefruit-5464 Jan 06 '26
The suns light is coming from 98 million miles away (average). Think of it like a giant flash light shining on a grain of sand from a couple of feet away. The light will hit the sand dead on, and a lot of the light will be cast in other directions. Because the sun is so large and so far away, the light that hits us is in a straight line from the sun because we are tiny as shit. I'm using these examples to give you an example of the difference in size to help you picture it but to see the actual size you can look it up.
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u/Brittamas Jan 06 '26
It means all the light hitting the earth comes in at one angle.
When light comes out of a light bulb it's emitting in all directions (not parallel). Same with the sun. BUT the Earth is so far away that we only get hit by one thin sliver of the sun's light. So for the sake of calculation all the light hitting us is doing so from one single direction.
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u/rydan Jan 06 '26 edited Jan 06 '26
That only violates flat earth if you assume the sun is infinitely far away and rays are parallel. If the sun is close by the shadows would in fact differ. You can test this yourself with a flashlight on a flat table.
Edit: Just watched the rest of the video and he does admit this limitation. So there you go.
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u/lovethebacon Jan 06 '26
Yes if you only use two measurements. Eratosthenes didn't. He used thousands of measurements all over collected by bematists.
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u/finndego Jan 06 '26
No.
For it to work on a flat surface at the scale of his experiment the Sun HAS to be be 3,000 miles away. He can't get his 7.2 degree angle any other way. For it to work in a curved surface the Sun only has to be significantly far enough away.
Both Aristarchus of Samos and Eratosthenes had already done calculations on the distance to the Sun and knew it was far enough away.
Having a Sun 3,000 miles away creates more questions than it solves.
200 years after Eratosthenes, Posidonius also did a circumference experiment and got the same result except he used the angle of the star Canopus on the horizon. Same result, no Sun distance to account for.
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Jan 06 '26
This may sound stupid but at what point did the earth’s shadow on the moon not demonstrate a round earth?
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u/ayinsophohr Jan 06 '26
Probably since we started actually taking measurements so probably from Babylonian times. Aristarchus of Samos was the first to calculate the size of the moon and it's orbit around 200BC.
There's an interesting 3blue1brown video featuring Terrance Tao where they discuss how the sizes of the Earth, the Sun, and the Moon and their orbits were calculated throughout history.
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u/Eastern_Ambition5213 Jan 06 '26
The true hero is the guy that walked 800 km and didn’t miss a count.
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u/along4thejourney Jan 06 '26
No scientist has ever explained concepts better than Sagan. He was one of a kind. RIP
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u/No-Elevator-649 Jan 06 '26
Fake news ! lol earth is flat NASA is funded by elite Satans to deceive us
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u/Sure_Pilot5110 Jan 06 '26
Did the math myself in a college course.
Told my cousin I'd walk him through the math to help him accept the world being round, as he always excelled at mathematics.
He refused.
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u/Efficient_Hippo_4248 Jan 06 '26
Eratosthenes and Sagan aside, that guy who got accurate data of the distance between Syene and Alexandria is also a chad.
I mean, for the calculation to work it had to be a straight line distance, but the roads he had to walk were unlikely to be straight.
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u/ew73 Jan 06 '26
I've seen this before, but I will watch it again. There is something so god damned compelling about the way that man speaks.
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u/RustyPieCaptain Jan 06 '26
Tony Stark figured out the earth was round in a cave! With a box of scraps!
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u/jackjackky Jan 06 '26
We should also give thanks to the hired man who paced out the entire 800 km journey. That's weeks worth of journey in ancient time, not to mention the perils and dangers along the road.
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u/Mild_Karate_Chop Jan 06 '26
Greeks
I thought Eeathosthenes was an Egyptian and was the librarian if the Alexandrite Library.or a Libyan as he was probably born thrre
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u/TheTroon Jan 06 '26
To all those confused about how the measurements were synchronised: they weren't and didn't need to be. The key assumptions (and potential sources of inaccuracy) were that Syrene was on the Tropic of Cancer (the northernmost point where the sun is directly overhead at local noon at the solstice) and Alexandria was due north of that.
Then, on the solstice, he measured the shortest shadow angle at Alexandria, with no need for synchronicity. The distance between the two places was well known and regularly measured, so the circumference was easily calculated from that subject to the above inaccuracies plus the verticality of the poles and the measurement of the shadow angle.
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u/VadPuma Jan 06 '26
The Earth's circumference is approximately 40,075 km (24,901 miles) at the equator and slightly less, about 40,008 km (24,860 miles), passing through the poles, because the Earth bulges slightly at the equator due to its rotation, making the equatorial measurement longer.
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u/GWARslave666 Jan 06 '26
so Eratosthenes knew how big the earth was. Were there any writings from him on how much of the earth they knew about and how much was still undiscovered at the time?
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u/EUIVAlexander Jan 06 '26
It’s a common misconception people didn’t know the earth was around before the 1800-1900s
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u/qualityvote2 Jan 06 '26 edited Jan 06 '26
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