Help replicating Eratosthenes' experiment

[I like Serena]

Using your measures we find an angle of 75 degrees, we are currently working on calculating the circumference of the Earth with our values.

Good!
Btw, I've looked up what my angle should really have been, which is 74.2 degrees.

We found out the distance between the parallel of our city is 1400.
75-62,5 = 12,5 degrees
(1400x360)/12,5 = 40320km ! So there's less than 0,6% of error from the modern value of 40075km.

Shouldn't it be 931 km instead of 1400 km for the distance between our latitudes?
My latitude is 52.37919 and yours is 44.01211.
With an Earth circumference of 40075 km that is a distance of 40075 x (52.37919 - 44.01211) / 360 = 931 km.

 

[dmc_lat47]

Hi:
I've been thinking of replicating this experiment in the US, and I came across this thread.

Google Maps places the latitude and longitude of Frenchies in the Duchy of Uze's, and ILikeSerena in Amsterdam.
It further says that the distance between those two locations is 1174 km via A31, and it curves a bit.
My calculation of the distance based on latitudes (~111 km per degree latitude) is 928Km.

Which makes the circumference quite a bit off. Sorry!

I'm wondering if the frenchies had any thought about the factors contributing to this error? How
did you guys come up with the distance of 1400m?

thanks
david

 

[rude man]

Maybe this is a misunderstanding, but the time of the sun's culmination is the local noon. Or do I misuse the word?

In english the sun's maximum height above the local horizon ("local apparent noon") is called the zenith. The local time of local apparent noon varies with time of year due to a little problem known as "the equation of time". This variation is approximately 2/3 due to the Earth's tilt with respect to the solar plane and 1/3 due to the ellipsicity of its orbit around the sun. The following will give you an idea how local noon varies with local time over a year:

 

[rude man]

BTW this is a good opportunity to remind any who need it or who lived in ignorance thus far that the roundness of the Earth was known WELL before Columbus! (about 1700 years before!)

 

[I like Serena]

Google Maps places the latitude and longitude of Frenchies in the Duchy of Uze's, and ILikeSerena in Amsterdam.

Yep. I'm working in Amsterdam, which is where I did my mid-day measurements.
Turns out that a couple of colleagues saw me, and they were wondering what I was doing.
Their best guesses were:

• Watching the wall to figure out if I wanted the same type of stone somewhere near my house.
• Measuring the height of a tower some distance off.

I had to disappoint them, and explain that I was measuring the circumference of the earth, which drew some 'yeah-right' glances. ;)

 

[haruspex]

BTW this is a good opportunity to remind any who need it or who lived in ignorance thus far that the roundness of the Earth was known WELL before Columbus! (about 1700 years before!)

Furthermore, Columbus' detractors at the time said he could not succeed because it was much too far. Had the Americas been another few days of sailing away mutiny would have put an end to matters.