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Homework Help: Help replicating Eratosthenes' experiment

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  1. Nov 27, 2017 #21

    Thanks a lot for your participation. We will use all that you mention in our work. We will be doing the experiment on the first of december at our local noon, if you think you can make it on your local noon please keep in touch.
     
  2. Nov 27, 2017 #22

    OmCheeto

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    Going through the thread from the start, it looks as though Haruspex had the best method, IMHO.

    And as I pointed out the other day, I'm 1/3 of the world away from you, in longitude. I think that would make my measurements meaningless, unless we knew how much our shadow lengths change each day. I would recommend we take measurements at least 2 days in a row.

    ps. My local weather report tells me that I might be a bad lab partner around that date. :redface:
     
  3. Nov 28, 2017 #23

    I like Serena

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    Hi Frenchies! :)

    I may be able to do the measurement for you.
    My location is latitude 52.379189 and longitude 4.899431. If I'm not mistaken that's at a nice distance almost straight north from you girls. :cool:
     
  4. Nov 30, 2017 #24

    I like Serena

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    Just checking, how are you gals, Maylis, Clara, and Hélèna, doing with practicing your English? :oops:
     
    Last edited: Nov 30, 2017
  5. Dec 1, 2017 #25

    I like Serena

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    Well, turns out I just couldn't make out any shadows with the current cloud cover.
    So instead I've marked 2 spots that are 1 meter vertically apart on the wall of a building.
    Then I looked directly at the sun, which I could still make out without burning my eyes due to the thin cloud cover.
    And with my eye at the same level as the lower spot (along a seam in the wall), I aligned the sun with the higher spot.
    Measuring the distance I got 3.75 meters with an estimated accuracy of about 0.25 meters.
    I measured it at my local noon, which is 12:29.
    That's about the best I can do right now, and in the meantime the cloud cover has thickened, so that I can't make out the sun any more.
     
    Last edited: Dec 1, 2017
  6. Dec 6, 2017 #26

    I like Serena

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    Hey Frenchies!

    Did you ever complete the experiment?
    I'm actually feeling at bit dissatisfied, since I still don't know the circumference of the earth with our measurements...
     
  7. Dec 7, 2017 #27
    Hello thank you a lot for the investissement you put into doing the experiment. We couldn't be working on our project this week. We actually did the experiment and measured the angle (wich is located up the stick) (we found approximatively 62,5 degrees), using different propreties (sinus, cosinus and pythagore) maybe we can achieve to calculate your angle and calculate the circumference of the Earth. But the main point is to prove that we do not have the same measures.

    Thank you a lot for your response
     
  8. Dec 7, 2017 #28
    Guys.. They are in the 11th grade, you're over complicating it.
     
  9. Dec 7, 2017 #29
    Using your measures we find an angle of 75 degrees, we are currently working on calculating the circumference of the Earth with our values.
     
  10. Dec 7, 2017 #30
    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.
     
  11. Dec 7, 2017 #31

    I like Serena

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

    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.
     
  12. Jun 1, 2018 #32
    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
     
  13. Jun 1, 2018 #33

    rude man

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    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: upload_2018-6-1_13-36-35.png
     
    Last edited: Jun 1, 2018
  14. Jun 1, 2018 #34

    rude man

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    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!)
     
  15. Jun 1, 2018 #35

    I like Serena

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    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. ;)
     
  16. Jun 2, 2018 #36

    haruspex

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    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.
     
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