Chillicothe, Ohio , USA, Unioto High School

latitude:39.367°
shadow: 79.1cm
angle: 38.344°

Greetings from Chillicothe, Ohio! Our 12th grade physics class divided into groups and gathered our data on September 21, 2007. Local noon was at 1:23 pm, so a team of students met at 1:05 pm and started to take measurements at 1:11 pm. We used rectangular meter sticks taped to bricks. We checked with a level to be sure the meter sticks were perpendicular. We had poster boards taped together under the meter sticks. We marked the edge of the meter stick, then the shadow’s edge every two minutes until 1:41 pm. Here are some pictures of the Measuring Team at work.
When our measurements were complete, the rest of the student teams went to work. They measured the length of each shadow line to find the shortest one, then they used trigonometry to find the sun angle measure. To do this, they found the ratio of the shortest shadow’s length in cm divided by the meter stick’s length of 100 m, then used inverse tangent (tan-1) to find the angle measure. Most of our angles were near 38 degrees.

The next step was to choose a school in the Southern Hemisphere and combine our data with theirs. Their angle and our angle were added to find how large of a slice of the earth’s total angle measure from N to S we had combined. For instance, if their angle was 32 and ours was 38, we had a total of 70 degrees combined. By multiplying this angle measure by 111 kilometers per degree, we found the N – S distance between our locations.

Then we took 360 divided by 70 degrees to find the number of “slices” of this size in the whole earth. Finally, we multiplied the number of slices times the number of kilometers per slice to find the earth’s circumference. All of our teams were under 5% error. Until next year – this is Unioto High School, over and out!!

Lafrançaise, France

shadow: 94.5cm
angle:43.333°