Sticks

It was two sticks! Stop spreading misinformation here!

Two sticks and a gigantic globe of plasma shining near-parallel beams of light at every spot on the planet.
- That was just kind of hanging around there, so why not use it?
- Also a dude he paid to walk a few hundred miles.
- Shit, I wanted to reproduce his experiment but I don't have one of those.
- Now I wonder what "Aaaaakshually" sounds like in ancient Greek.
- Smh my head, scientists still don't have stable fusion, when Erastosthenes was using it as a constant in his experiments.

Say his name.

https://en.m.wikipedia.org/wiki/Eratosthenes

Just for those who wish to learn more.

The sieve guy?
- Yes.
His nickname was "Beta" because he was the second best at everything.
Big brain both literally and figuratively based on that etching.
How do you pronounce it? I'm fumbling
- "Eratosthenes"
  era TOSS the knees

The original "Tony Stark In a Cave"

Eratosthenes did it with a fucking stick .
But we are not Eratosthenes sir .

The accuracy he achieved and in that time period with the information available to him is frankly staggering. The degree of his error is slightly complicated by the stadion not being a historically exact figure, but his calculation showed the Earth to be 252,000 stadia in circumference. Accounting for the variability in the exact length of the stadia dependent on what definition was used in the calculation, that gives us in kilometers 39,060km on the lower end and 40,320km on the upper. The actual circumference of the Earth is 40,075km. This gives him an error range of between -2.4% and +0.8%.

He also didn't just use a stick but used extensive geographic charts to calculate the distance between the 2 cities where he measured the shadow. It was a monumental achievement and is shockingly accurate. I also believe this knowledge was lost to time and for quite a long time after we did not have any measurements even close to this accuracy.

Here is a picture visually demonstrating how he performed his calculation.

It's still seriously impressive with that error range?
- I never said it wasn't. I was originally writing this as a response to a commenter who said the error was ~15%. My comment initially started with "He was actually significantly more accurate than that."
- Good question

how many sticks then?
- two
- A whole bundle of them tied together.

He was obviously employed by NASA. Don’t believe the round earth agenda!

Sheeple never stop to amaze me!
The ground that looks and feels flat is actually flat? Impossible!
A guy 2200 years ago measures how round earth is - with a straight stick? Sure sounds right!
/s
To play devil's advocate, wouldn't you get the same result on a flat earth, if the sun was closer enough for rays not to be parallel?
- I’m not completely sure, but I guess it’s difficult to fit a flat earth model if you have three or more measurements.

2 sticks

sticks and stones can cucumberference the big rock

Sagan did a bit on this.

https://www.youtube.com/watch?v=G8cbIWMv0rI

isnt this the fucker who used units of stadia? The unit that we have no historical reference to? (at least one significant enough to be certain about it's actual referenced distance) Which means that we don't actually know how accurate it was?

I mean we do know the formula, se we know pretty well how accurate it was, since we can just use the same formula with meters and calculate it ourselves
"The simplified method works by considering two cities along the same meridian and measuring both the distance between them and the difference in angles of the shadows cast by the sun on a vertical rod (a gnomon) in each city at noon on the summer solstice. The two cities used were Alexandria and Syene (modern Aswan), and the distance between the cities was measured by professional bematists.[16] A geometric calculation reveals that the circumference of the Earth is the distance between the two cities divided by the difference in shadow angles expressed as a fraction of one turn. "
Sorta. The stade was based on the pous which varied. But not that much, and in ways that are often consistently documented. Around the time Eratosthenes was alive, give or take a couple hundred years, it was documented that 1 Roman mile = 8 stades, which gives us something to go of off. While there are other possible definitions, we do have one that we know is probably closest to whatever Eratosthenes used.
EDIT - the numbers regarding the error range in this source is likely inaccurate, but goes into the units issue
https://maa.org/press/periodicals/convergence/eratosthenes-and-the-mystery-of-the-stades-how-long-is-a-stade
- +/-20% error isn't terrible on a conversion. The fact that it's only 10% offset is crazy though.

When I was a kid my teachers told me that Christopher Columbus discovered the earth was round and that before him everyone thought it was flat. When I was about ~13 I read a short biography of Eratosthenes and it blew my little mind.

THE PYRAMID ALIENS

There were also wells and a lot of walking involved.