Solar Insolation and the Globe-kin

In this festive, fall themed activity, I worked with a group to create a replica of the earth on this pumpkin.

Once the Globe-kin was completed, we used a heat lamp to mimic the sun in our scenario, and then adjusted the globe-kin to 23.5º away from the "sun." We taped a temperature probe to a location we marked off as "us" meaning, where we are located, meaning Pennsylvania. We taped a piece of string to our location, marked by a star, and the to the end of the lightbulb of the heatlamp. This gave us our angle of insulation, which turned out to be 20º, which is not too far from the actual angle of insulation of the earth relative to the sun. The winter data we collected was as follow:

Initial temperature: 21.2º C 

Minute 2: 24.6º 

Minute 3: 25.6º 

Minute 4: 26.9º 

Minute 5: 28.5º 

 which meant a 7.3º change in temperature

The next test we decided to recreate was the same thing, but in summer. All we had to do to make this change was tilt the pumpkin 23.5º towards the sun, instead of away, like in the winter. (It should be noted that in this experiment we used the stem as a stand in for the north pole, or the axis) We got the following data:

Initial temperature: 24.9ºC

Minute 0.5: 29.1º

Minute 1: 33.4º

Minute 1.5: 37.0º

Minute 2: 39.3º

Minute 2.5: 41.3º 

Minute 3: 42.4º

Minute 3.5: 43.4º 

Minute 4: 44.5º

Minute 4.5: 45.6º 

Minute 5: 46.5º

meaning a 17.4º temperature change 

Hypothesis: The temperature in PA will go up when the sun shines directly on it, and will be higher in the summer.

While it seems as though the temperature would be higher in the winter, because the earth is closer to the sun, it is not so. The angle of insolation is what changes the temperatures, also known as solar insolation. What really affects temperature is not the earth's distance to the sun, but the angle of the sun's rays on the planet. Since the sun is shining directly on the earth's surface in the summer, it is warmer than in the winter, when it is at 45º instead of 90º.