The library of Eratosthenes

september 23

Sunday 23 September 2007 by perbosc

Lafrançaise, Auckland, Pachuca


Photo by Laure (5 ° 1) at her home on Sunday, for the autumnal equinox.

 Auckland , New Zealand

  • Date: 23/09/2007
  • Shadow/Ombre: 78,3cm
  • Angle: 38°
  • We are a home school family in Auckland New Zealand. We are Year 6 which is equivalent to Grade 6 USA. We are starting this experiment with great pleasure. We are looking forward to do the activities and the noon day itself. Our location is: Latitude: 36°52’03" South Longitude: 174°48’12" East We found this on Google Earth. We are in Spring time here down under with the sun shining most days. Let’s hope it’s sunny on the DAY!

     Pachuca, México

    lat: 20°07’ N long: 99°44’ W

  • Date: 23/09/2007
  • Angle: 28°18’
  •  Greenfield Park (CANADA)

    St. Jude School : Final Report

    Our school is located in a suburb of Montreal, Canada, at 45:29N (latitude) and 73:29W (longitude). We are 28 students in grade 5(class5IA). Our teacher, Mrs. Mirza introduced this project to us in September. She explained to us how Eratosthenes performed a simple experiment 2200 years ago to measure the circumference of the Earth. His calculation is still considered accurate today by scientists.

    We went on the Noonday website and did some research. At first, the whole idea appeared quite complicated to us. Most of us had trouble understanding some ideas and how they were going to help us determine the circumference of the Earth. But as we got more involved, the process started to become clear.

    We carried out the shadow measurements on September 21 st 2007, which was as close as we could get to the Autumn Equinox (September 23 rd). The shadow measurements (99cm) at high local noon time (12:48pm) helped us determine our sun angle which was 44 degrees.

    The next step was to choose a partner city whose sun angle could help us find the central angle. We decided to select Abba’s Orchard in Philippines, as it is far away. Their sun angle was 8.4 degrees. The difference between the two became our central angle, that is, 35.6 degrees.

    Now Mrs. Mirza showed us how the central angle could be compared to a slice in a big circle. We could then understand that the arc of the central angle represented the distance between the two cities. Once we knew the North/South distance between us and Abba’s Orchard, by subtracting the 2 latitudes, we could then multiply the arc’s length with the number of slices in a circle. These are some of our calculations:

    No. of slices= 360°divided by 35.6 degrees=10.1

    N/S distance= 4 116.25 km

    Circumference of the Earth = 4116.25x 10.1 = 41, 574.12 km

    Conclusions : We learned a great deal from this project. We now know how knowledge of angles helps us in real life, how the circumference is calculated and much more. Before doing this project we didn’t know a lot about latitude and longitude and what these lines help us find on the globe.

    All of us are very proud of our learning. We can see how Math, Science and Technology work together in any scientific study.

    Students of Class 5IA

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