To examine how distance and inclination affect the amount of heat received from a heat source.
This lesson was developed by the Challenger Center as part of NASA's MESSENGER Mission, of which Science NetLinks is a partner.
In this lesson, students discuss what heat is and how it travels. They discover that one way to cool an object in the presence of a heat source is to increase the distance from it or change the angle at which it is faced. Students perform experiments that measure how the heat experienced by a test subject changes as the distance or the viewing angle changes. Students learn to distinguish which effect is more important for determining the seasons on earth. They also learn how the MESSENGER mission to Mercury takes advantage of these passive cooling methods to keep the spacecraft comfortable in a high-temperature environment. Refer to the Science Overview of the lesson for a summary of the science content relevant to the activities in the lesson. In order to successfully complete this activity, students should already have some familiarity with thermometers and protractors and have some prior instruction in heat and energy transformations. Refer to the Lesson Overview for a more detailed explanation of what students will learn from the lesson.
The distance of the earth from the sun ensures that energy reaches the planet at a rate sufficient to sustain life, and yet not so fast that water would boil away or that molecules necessary to life would not form.
The motion of the earth and its position with regard to the sun and the moon have noticeable effects. The earth's one-year revolution around the sun, because of the tilt of the planet's axis, changes how directly sunlight falls on one part or another of the earth. This difference in heating different parts of the planet's surface produces seasonal variations in climate. The rotation of the planet on its axis every 24 hours produces the planet's night-and-day cycle—and (to observers on earth) makes it seem as though the sun, planets, stars, and moon are orbiting the earth.
The earth has a variety of climatic patterns, which consist of different conditions of temperature, precipitation, humidity, wind, air pressure, and other atmospheric phenomena. These patterns result from an interplay of many factors. The basic energy source is the heating of land, ocean, and air by solar radiation. Transfer of heat energy at the interfaces of the atmosphere with the land and oceans produces layers at different temperatures in both the air and the oceans. These layers rise or sink or mix, giving rise to winds and ocean currents that carry heat energy between warm and cool regions. The earth's rotation curves the flow of winds and ocean currents, which are further deflected by the shape of the land. (Science for All Americans, pp. 42–43.)
Finally, while teaching, keep in mind that middle-school students who can use measuring instruments and procedures when asked to do so often do not use this ability while performing an investigation. Typically, a student asked to undertake an investigation and given a set of equipment that includes measuring instruments will make a qualitative comparison even though she might be competent to use the instruments in a different context. It appears students often know how to take measurements but not of what or when. (Benchmarks for Science Literacy, p. 360.)
Ideas in this lesson are also related to concepts found in these Common Core State Standards:
- CCSS.ELA-Literacy.RST.6-8.3 Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.
- CCSS.ELA-Literacy.RST.6-8.7 Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table).
Note: Parts of this lesson were extracted from the unit, Staying Cool, developed by the Challenger Center as part of NASA's MESSENGER Mission.
Have students do the Warm-Up and Pre-Assessment section of the Lesson Plan, where they consider the idea of heat transfer, and how the effects of the sun might differ on Earth and Mercury based on their distance from the sun. The idea of inclination is also introduced, and students ponder its effects and contrast it with distance. In addtion, students should fill out a KWL Chart to find out what they already know and want to learn about heat based on distance and angles, and how these things affect seasons on earth.
Divide the class into groups of three and have them perform Part 1: Effects of Distance in the Procedures section of the Lesson Plan. In this experiment, students will set up two thermometers at different distances from a light bulb and record their temperatures to determine how distance from a heat source affects temperature. Have each group follow the instructions on the Distance and Inclination student sheet to set up the experiment.
For Part 2: Effect of Inclination, groups of five will assess the effects of inclination by constructing a device designed to measure the temperature inside a black construction paper sleeve, and place the device at different angles toward the sun. The Distance and Inclination student sheet will be needed to guide the class through this experiment.
Finally, review and discuss your students' findings using the questions and activities in the Discussion and Reflection section of the Lesson Plan. In addition to considering how their results could relate to the seasons on earth, students will be informed about the MESSENGER mission and asked to consider how MESSENGER mission designers have used the concepts presented in this lesson. (The MESSENGER mission will use two cooling methods that take advantage of the effect of distance and inclination to help keep the spacecraft comfortable in a high-temperature environment. Moreover, the spacecraft's solar panels will not view the sun directly, and a safe distance will be kept from Mercury's sunlit areas in order to limit the amount of radiation received from those surfaces.) Copies of the Staying Cool with MESSENGER student sheet and the MESSENGER Information Sheet will be needed for these discussions.
Answers to questions on both student sheets can be found on the Teacher Answer Key.
Have students review and discuss the topics in the Closing Discussion section of the Lesson Plan, which includes reminding them of how they have demonstrated that the simple methods of increasing distance or changing the viewing angle can be effective for cooling in the presence of a heat source.
Student understanding can be assessed by how completely they recorded their results in the charts on page 5 of the Distance and Inclination student sheet and how they make the graphs of their data. Their understanding of their results can be further evaluated by their answers to the questions on pages 6 and 7 of the Distance and Inclination student sheet as well as the Stayng Cool with MESSENGER student sheet.
For related Science NetLinks lessons, see:
Further demonstrate the effects of distance and inclination with thermal strips that change color depending on temperature. Attach a thermal strip to a globe so that it runs along a line of longitude. Place the globe in the sunlight so that the equator is at an angle to the sun's rays similar to the earth obliquity of 23.5 degrees. After a few minutes, there should be a noticeable difference between the color of the thermal strip at the equator and at the poles.
Have students design an experiment to determine which effect is more important in a given situation, distance or location.
Have students perform Part 1 of the experiment at various distances from the light bulb and graph their results. (The x-axis should be labeled "Distance" and the y-axis, "Change in Temperature.") Ask them to first draw a prediction line on the graph paper of what they expect to happen. Then have them plot their data and compare it to their predictions. Next, have them graph the 1/R (squared) law and see how well their data fits the theory.