Seasons and why the equator is warmer than the poles gas and electric credit union

One of the most common and persistent scientific misconceptions is that Earth’s seasons are caused by Earth’s distance from the sun. A closely related and perhaps more common misconception is that the equator is warmer than the poles because the equator is significantly closer to the sun than are the poles (i.e. the equator "bulges out" toward the sun). Even professional geoscientists sometimes hold the latter misconception. It is, for example, stated as fact in one of the (to remain nameless) "Geology Underfoot" series of guidebooks. Many people combine the two misconceptions. For example, many people know that the southern hemisphere experiences winter while the northern hemisphere experiences summer (and visa versa), but they explain this phenomenon by erroneously stating that the northern hemisphere is closer to the sun in June than it is in December because Earth’s tilt toward the sun in June makes the northern hemisphere "bulge out" toward the sun.

The guided-discovery activity described here helps students confront and overcome both of these common misconceptions as it guides students toward an understanding of how and why the angle of incident sunlight determines the intensity of the solar energy that strikes the ground and hence how the angle of incident sunlight can be used to explain both seasonal and latitudinal differences in temperature. Along the way, this activity helps students visualize the true dimensions of the solar system and the various objects within it. This seemingly unrelated topic is included in this activity because an accurate perception of the scale of the solar system helps students understand that (1) Earth’s equator is not significantly closer to the sun than are its poles, and (2) all sunrays intercepted by Earth are essentially parallel to each other, whether they strike the equatorial or polar regions — a concept that is essential for understanding how and why the angle of incident sunlight varies systematically with latitude and season. Learning Goals

General Comments: This activity can be completed in two hours if students give it a superficial treatment, but three to four hours are required for an in-depth exploration, including the confrontation of any misconceptions and the construction of a full understanding of the concepts.

As students work through these activities, encourage them to engage in lively conversations, continually brainstorming, questioning, and checking for consistency. In my experience, students are often inconsistent — gently call them on this. For example, one student adamantly insisted — despite the protestations of her team members — that the equator was not significantly closer to the sun than were the poles. Yet, she then attributed the temperature differences between the equator and the poles to differences in their distances to the sun. I pointed out that she was contradicting herself, which caused her to engage in some deep thinking which culminated in an "Aha!" moment that she absolutely delighted in.

I recommend doing the outdoor activity as a whole class with student volunteers to represent each planet; choose the tallest person in the class to pace off the distances. When you get to "Earth," have the students place the moon at the appropriate distance from Earth and point out that, coincidentally, the moon and sun look the same size as seen from Earth.

Place the globe on a counter so that it is tilted to the right or left (i.e. Spring or Fall position) with the Pacific Ocean facing the overhead projector — having a relatively featureless part of the globe face the projector helps students see the grid projected on it more clearly, without being distracted by the details of complex shorelines or borders.

Before students begin this activity, explain to them that each group will be asked to formulate an initial hypothesis to explain the causes of the seasons. The students will then try to use this hypothesis to explain a series of facts. If their hypothesis is not up to the task, they must discard and reformulate, modify, or add to their initial hypothesis until it can provide a satisfactory explanation of the facts.

At the end of this activity, I typically assess student learning by having student groups present their answers to the rest of the class. I divide the different parts of this activity among the student groups, assigning each group to prepare illustrations and orally present their part to the rest of the class. Each presentation is then followed by a whole-class discussion.

I assign this Homework Assignment on the Causes of the Seasons (Microsoft Word 58kB Sep5 09) as assessment, but also as a way for students to consolidate the understandings that they have built during the guided-discovery activity. Students often benefit from a formal traditional presentation of concepts that they have previously struggled to grasp while working through a hands-on guided-discovery activity. When the traditional presentation follows guided discovery, it can be very meaningful, building students’ confidence in their freshly hatched ideas and organizing their discoveries into a logical and elegant construct. Without some kind of traditional presentation of the concepts, students are often so unsure of themselves that they feel lost. Yet, in my classes, students rarely complete (let alone comprehend the material presented in) a "Read Chapter 3" type of assignment, even when it’s followed by a quiz. But the vast majority of students will complete an assignment like the one presented here, which requires students to extract and record specific information from the textbook. Higher-order thinking it’s not, but it is a helpful incentive to encourage students to open their textbooks and actually comprehend what is written there.