The library of Eratosthenes


2005 by astro.perbosc

school : Sekolah Alam School
city : Jakarta
country : Indonesia
address :
postal code :
latitude : 06°20’ S = -6,333°
longitude : 106°49’ E = 106,817°
year : 2005

date : 25/03/2005
gnomon 100cm
shadow 14cm
angle : 7.970°
Ourschool, Sekolah Alam, which could be best translated in english as "the Natural school" , is an environmental-based school, whose vision is to enable children to learn from the wishdom of their surounding nature. Most of the activities are done outdoor, in order to maximize the student interaction with nature. Therefore when we heard about the noonday project we were quite eager to register. since this kind of activity is quite aligned with our teaching method.

Because of our 7th Grader is a small class consists of 4 students (2 boys and 2 girls), we decided to only plane for a single group observation. We are a bit worry about the weather condition, since february until april are a "pancaroba" (transitional) months between rain and dry season. In those months the weather is very unpredictable. What happened is that we couldn’t start the observation until the last day (March 25th) because of the cloud and rain during the 22th - 24th.

The last day is actually a holiday (easter holiday) but since the group is very eager to carry out the observation, they are willing to sacrifice their holiday to come to school that day... what a spirit !!! We prepare the observation station in the center of our football field, in order to avoid any obstruction at all. The field preparation was started on 10.00 AM in order to have enough time before noon. The measuring device is made from bamboo stick and, on the direction of the sunlight we laid a tracing paper. Since we are living very near to the equator, unlike the location in sub tropic area, we always had a very short shadow during noon, so we wre only prepare les than 50 cms long paper trace. The students had been previously trained about the theoritical aspect of the project by using the material from the project website and also from other resources, especially for the trigonomtery aspect.

The measurement stared at 11.15 AM and the measurement was made every 15 minutes. At 11.15 the shadow length was 26.2 sm.. and at noon the shadow reach the shortest length of 14 cm before increasing again until 22 cm (at the opposite direction) at 12.30.

After the measurement the tracing paper were taken back to the classroom to be re-measured for accuracy. Then by using Micrsoft Excel spreadsheet we calculated the sun’s angle at the shortest shadow at noon time.

From the datasheet in the project’s website, we choose as the partner site the data from Charles Brant Chesney Elementary school in Duluth Georgia because of the proximity in observation date. The result is quite amazing we’ve found that the earth’s circumference is 40,007.88 km !!, which is prety close to the benchmark of 40,008 km.

The students were very proud about the experiments, and the most important thing is that now, they have new reason to fall in love with science !!!!

Thanks for all

Novi Hardian 7th Grade Teacher Sekolah Alam Jakarta Indonesia

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