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MSP:MiddleSchoolPortal/The Reasons for the Seasons

From Middle School Portal


The Reason for the Seasons - Introduction

Seasons lg.jpg

Understanding why the Earth has seasons is one of the most difficult concepts for students to understand, and it is often a battle to get them to abandon their preconceived ideas. Two widely held misconceptions are:

  • Earth's orbit brings it closer to the sun in summer and farther away in winter. This idea neglects the fact that at any given time the Northern and Southern Hemispheres experience opposite seasons. In fact, earth's orbit is actually nearly circular, and so variations in distance from the sun have little effect compared to the effects of changes in the angle of incoming sunlight.
  • The hemisphere that is tilted toward the sun experiences summer because it is closer to the sun. Actually, earth is so small compared to the sun, and so far away from it, that the difference in distance between the two hemispheres and the sun is inconsequential. However, the tilt of earth's axis does affect the angle at which the sun's rays strike earth—called the angle of incidence—this is what causes the seasons.

Interviews with Harvard graduates in the late 1980s illustrate how widespread these misconceptions about the seasons are. When asked what causes the seasons, most of the newly graduated students gave the same wrong answer that many people give: the seasons are caused by earth getting closer (or farther) from the sun. The section on Misconceptions of this publication provides a wealth of resources that will help you understand, uncover, and change your students’ preconceived notions of the seasons and other science concepts.

Contents

We have also included classroom activities in which students use real-time data and their own observations to explain why the seasons change as well as resources that talk about how different cultures over the millennia have explained the changing of the seasons.

Background Information for Teachers

The reason for the seasons cannot be explained in one simple sentence. Rather several concepts have to be grasped independently and then integrated for a full understanding. So where should we begin? The NSDL Strand Map Service provides guidance. These maps illustrate connections between concepts and across grade levels. An image of the middle grades (6-8) only part of the Weather and Climate map appears below. Clicking on a concept within the maps will show NSDL resources relevant to the concept, as well as information about related AAAS Project 2061 Benchmarks and National Science Education Standards. Move the pink box in the lower right hand corner of the page to see the grades 6-8 learning goals. If you go to the entire K-12 Weather and Climate map, you see that the full integration of concepts is recommended to occur in high school. But when you consider many high school students can graduate without an earth science course, this may be their last formal instruction in the reason for the seasons. Students often absorb more challenging concepts than we sometimes give them credit for, especially when they are on the receiving end of well scaffolded, quality instruction.

These two sites provide overviews of astronomy that include in-depth descriptions of how the seasons occur.

Astronomy of the Earth's Motion in Space In this algebra-based overview of pretelescope astronomy, the topics covered include sundials, seasons, calendars, precession, shape and rotation of Earth, Greek astronomy, heliocentric theory, and Kepler's laws. It also has sections on the Moon and how its distance was found. Many historical details, stories, and applications are included.

Seasons This section of the web site Astronomy Without a Telescope provides an explanation of why the seasons occur on Earth as well as information about seasonal changes on the other planets in our solar system. Other sections of the site describe the celestial sphere, coordinate systems, the motion of the stars, time zones, the phases of the moon, solar eclipses, lunar eclipses, and the motions of the planets.

Timely Teachings: Seasons and the Cycles of Night and Day This link includes the archived recording of a webinar and related resources that discusses two challenging topics in the elementary and middle school curriculum - day and night and seasons from both science and literacy perspectives. They review scientific principles, examine common misconceptions and formative assessment strategies, and discuss how to approach these topics by integrating science and literacy. We'll share resources from Beyond Penguins and Polar Bears, the National Science Digital Libraries' Middle School Portal, and other high-quality content providers.

Misconceptions about the Seasons

The video documentary A Private Universe, produced by the Harvard-Smithsonian Center for Astrophysics, explores why so few students truly grasp basic science concepts. The video traces the problem through interviews with Harvard graduates and their professors, as well as with a bright ninth grader who has some confused ideas about the orbits of the planets.

You can download the video by registering at the Annenberg Media: Teacher Professional Development web site. Resources related to the research reported in A Private Universe are featured in Misconceptions about the Seasons. The video is also available from through Pyramid Film & Video, which offers a study guide at http://www.pyramidmedia.com/1225guide.pdf. Another lesson plan based on the video and developed by the American Association for the Advancement of Science is found at http://www.sciencenetlinks.com/pdfs/seasons_teachsheet.pdf. The following resources also use the Private Universe as a jumping off point for investigating students’ misconceptions.

A Private Universe Project The Private Universe Teachers Lab enables teachers to practice techniques of identifying student misconceptions and moving toward conceptual change in basic astronomy. This lab contains a survey to identify misconceptions and three in-class activities for grades 4 to 8 that help students gain an understanding of the phases of the Moon. There are teacher discussion forums on planning teaching sequences and learning how to adapt activities to different situations.

Private Universe Project: Workshop 5. Vision: Can We Believe Our Own Eyes? This video clip explores the origins of student ideas to find out whether experience equals learning. It shows how experience can work for or against learning because students can disbelieve concepts that they have "learned."

Private Universe Project in Science. Workshop 9. Constructivism: A Vision for the Future An example of an assessment item about the seasons is shown in this video clip.

A Private Universe This site describes and provides access to streaming video of the documentary A Private Universe, which is featured in the resources above. Links to related resources and ordering information for the video or DVD and teacher’s guide appear on this site.

Science and Myth

Throughout the ages different cultures have speculated on why the seasons happen as they do. The ancient Greeks thought that the seasons were the result of the unfortunate marriage between Persephone, the daughter of the goddess of the harvest, and Hades, the god of the underworld. Ancient Navajo Indians believed the seasons were caused by the aging of Estsanatlehi as the seasons passed from spring to winter until she was reborn with the next spring.

Over the ages, cultures have come up with wonderful stories to explain the phenomenon of seasons. At the same time ancient astronomers were remarkably accurate in their calculations and predictions of patterns in the cosmos. Only in the past few centuries have scientists formulated a model that can account for such diverse patterns as moon phases, the frequency and duration of lunar and solar eclipses, and seasonal fluctuations in day length or the sun's apparent path in the sky.

The following sites tell us more about the myths and the science of seasonal change.

Ancient Observatories: Chaco Canyon Why is your shadow longer in winter than in summer? It's easy to see the answer if you have a "sun" and an orbiting "earth" to demonstrate. Like many other ancient people, the ancient Chacoans used the annual changes in shadows to measure the passage of time and the change of seasons. In this activity, you'll see how the sun's tilt on its axis changes the length of shadows.

Precession About 2,000 years ago the Greek astronomer Hipparchus discovered that the position of the Sun at any season, measured against the background stars, migrates in a slow cycle of about 26,000 years. This "precession of the equinoxes" also shifts the position of the celestial pole (so that our pole star would not have been a good guide for the ancient Greeks) and is caused by the rotation axis of the Earth slowly moving around a cone.

Recording the Changing Seasons in Ancient Times In this lesson plan, students pretend to be historians and use web sites to find information about how ancient cultures kept track of and celebrated the seasons. The students compile their findings into posters or illustrated reports.

Lessons and Activities

These resources offer many opportunities for classroom activities and demonstrations that center on the relationship between the earth and the sun.

The Sun and the Earth This lesson plan helps students understand how the relationship between the Earth and the Sun affects the seasons. Students will describe the differences between the four seasons, diagram the Earth and Sun during different seasons; use a map activity; and write journal entries from the points of view of people living in different parts of the world.

A Reason for the Season This web site, part of National Geographic's Xpeditions Hall, provides lesson plans and activities. Using images and text, students learn why the seasons occur, how the seasons affect different animals, and how ancient civilizations celebrated and explained the seasons. A short quiz tests knowledge of the solstices and equinoxes.

The Earth's Orbit These 11 activities are from the online book Eyes on the Sky, Feet on the Ground, which provides explorations into astronomy as a classroom tool for learning how to theorize, experiment, and analyze data. The activities begin simply by trying to quantify the observation that it is colder in the winter and end by measuring the tilt of the earth. The activities are fully illustrated and contain detailed, step-by-step instructions as well as suggested discussion topics.

The Four Seasons In this activity, students learn that it is the tilt of earth's axis that causes the seasons. This resource is part of the Science NetLinks.

Teachers' Domain: Seasons on Earth This lesson will reinforce the concept that earth's seasons result from a combination of its orbit around the sun and the tilt of its axis, and help to dispel two popular misconceptions of what causes the seasons. Students will use class discussion, activities, and videos. They will also study satellite data showing seasonal changes of plant life and explore an example of long-term natural climate change.

Tilt-A-World The effect of the tilt of the earth on the seasons is emphasized in this lesson from Everyday Classroom Tools.

Seasons and Shadows: Investigate How Shadows Shift Throughout the Year In this activity, students can see how the sun's tilt on its axis changes the length of shadows.

Modeling the Seasons This activity provides instructions for students to model the seasons with their own earth globes. After students have modeled four dates (December 21, March 21, June 21, and September 21), they will have modeled a year, or one earth revolution around the sun.

Interactive Applets and Animations

These sites offer opportunities to see concepts presented in engaging animations.

Seasons This Flash animation shows the earth orbiting the sun and dates for the various seasons. In addition, it shows the declination of the sun throughout the year, as well as how a constant beam of sunlight gets spread out and concentrated as the sun changes altitude. This resource is from Demonstrations and Animations for Teaching Astronomy.

ASPIRE: Astrophysics Science Project Integrating Research and Education This teacher resource page contains interactive laboratory activities and is part of a series centering on astronomy, Earth science, and physical science concepts. The following lessons are from this resource.

Seasons Activity
Use a sundial to observe seasonal changes.
Seasons Exercise
Use seasons to determine your location.
Sun Angle Lab
This interactive lab helps explain how the temperature on the surface of the earth is affected by the angle of the sun. It also explains how the surface area of light cast upon an object changes in relation to the angle of the light source.

Observe Seasonal Changes in the Amount of Sunlight Reaching Locations on Earth This animation demonstrates how the tilt of the earth's axis causes seasonal variations in daylight. The introduction explains how the images, captured from a geostationary satellite positioned over Australia, were recorded daily from January to December. Students are instructed to look for the continent of Australia and to play the animation until they can identify the images that represent solstices and equinoxes. Movie controls allow students to repeat, pause, or step through the animation, which can give students more time to analyze the images.

Sources for Real Data

With these resources your students can use real-time data to investigate seasonal change factors.

Global Learning and Observations to Benefit the Environment (GLOBE) The GLOBE Program links students, teachers, and researchers in an effort to learn more about our environment. Students submit data in the fields of atmosphere, hydrology, soils, and land cover/phenology. The web site includes a mapping/graphing area, a teacher's guide, and an educators' forum. In the United States, GLOBE is led by a federal inter-agency program in partnership with colleges and universities, state and local school systems, and non-government organizations.

The following seven activities are from the GLOBE Teacher's Guide.

Limiting Factors in Ecosystems
The purpose of this resource is to illustrate how physical factors—temperature and precipitation—limit the growth of vegetative ecosystems. Students observe and record seasonal changes in their study site. They establish that these phenomena follow annual cycles and conclude the activity by creating displays that show the repeating pattern associated with the appearance and disappearance of seasonal markers.
Seasonal Change on Land and Water
To further students' understanding of the causes of seasonal change, the class reviews global visualizations of incoming sunlight and surface temperature. Students use the visualizations to support inquiry on the differences in seasonal change in the Northern and Southern Hemispheres, culminating in an evidence-based argument about why one hemisphere experiences warmer summers although it receives less total solar energy.
Modeling the Reasons for Seasonal Change
This activity demonstrates what causes the seasons by focusing on the earth's tilt and spherical shape. Students learn how sunlight spreads over the earth at different times of the year, emphasizing the solstices and the equinoxes. Students investigate the effect of the earth's tilt on the spread of sunlight by modeling different tilts using a three-dimensional polyhedron. Students also calculate the relative sunlight intensity received by the Northern and Southern Hemispheres.
How Do Seasonal Temperature Patterns Vary Among Different Regions of the World?
Students use GLOBE data and visualizations to display current temperatures on a map of the world. They explore the patterns in the temperature map, looking especially for differences between the Northern and Southern Hemispheres, and between equatorial regions and high latitudes. At the end of the activity, students discuss the relative merits of different types of data displays: tables, graphs, and maps.
What Are Some Factors That Affect Seasonal Patterns?
Students use GLOBE data and graphing tools to compare the influence of latitude, elevation, and geography on seasonal patterns. Students analyze the graph of the past year's maximum and minimum temperatures at their site. They compare this graph to similar graphs for two other sites and list which factors might cause the patterns to be different.
What Can We Learn About Our Seasons?
The purpose of this resource is to have students develop a qualitative understanding of the characteristics and patterns of seasons and highlight the relationship of seasons to physical, biological and cultural markers. Students observe and record seasonal changes in their local study site. They conclude the activity by creating displays that illustrate the appearance and disappearance of seasonal markers.
Operation Ruby Throat: The Hummingbird Project Protocol
The purpose of this resource is to observe seasonal migration patterns, feeding habits, and nesting behavior of Ruby-throated Hummingbirds in North and Central America. Students will learn how to identify male, female, and immature Ruby-throated Hummingbirds and to observe migration and feeding behavior. Students will learn how to make connections among hummingbird behavior and weather, climate, food availability, seasons, day length, and other environmental factors.

Earth Exploration Toolbook: Using GLOBE Data to Study the Earth System This chapter from the Earth Exploration Toolbook guides users through the process of locating and graphing data that has been collected by students who participate in the GLOBE Program. The GLOBE Graphing Tool is used to superimpose four different environmental data sets as a single graph to show otherwise hidden relationships. Seasonal changes in soil moisture are highlighted, as are the concepts of reservoirs and flux and the role of solar energy as a driver of flux. Additional investigations can be performed using this tool, methodology, and the GLOBE data set.

Journey North: A Global Study of Wildlife Migration and Seasonal Change K-12 students across North America share their field observations of wildlife migration and seasonal change. They track the coming of spring through the migration patterns of birds and mammals; the budding of plants; changing sunlight; and other natural events. Standards-based lesson plans, activities and information help students make local observations and fit them into a global context.

SMARTR: Virtual Learning Experiences for Students

Visit our student site SMARTR to find related virtual learning experiences for your students! The SMARTR learning experiences were designed both for and by middle school aged students. Students from around the country participated in every stage of SMARTR’s development and each of the learning experiences includes multimedia content including videos, simulations, games and virtual activities. Visit the virtual learning experience on Weather.

Careers

The FunWorks Visit the FunWorks STEM career website for youth to learn more about a variety of science-related careers including meteorologist and environmental scientist.

Latest Science News from the New York Times

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National Science Education Standards

These excerpts from the National Science Education Standards address topics and experiences students should have in the middle school.

As a result of their activities in grades 5-8, all students should develop an understanding of

Content Standard D: Earth and Space Science

Earth in the solar system

  • The sun is the major source of energy for phenomena on the earth's surface, such as growth of plants, winds, ocean currents, and the water cycle. Seasons result from variations in the amount of the sun's energy hitting the surface, due to the tilt of the earth's rotation on its axis and the length of the day.

Content Standard G: History and Nature of Science

History of Science

  • Many individuals have contributed to the traditions of science. Studying some of these individuals provides further understanding of scientific inquiry, science as a human endeavor, the nature of science, and the relationships between science and society.
  • In historical perspective, science has been practiced by different individuals in different cultures. In looking at the history of many peoples, one finds that scientists and engineers of high achievement are considered to be among the most valued contributors to their culture.
  • Tracing the history of science can show how difficult it was for scientific innovators to break through the accepted ideas of their time to reach the conclusions that we currently take for granted.

Developing Student Understanding

The understanding that students gain from their observations in grades K-4 provides the motivation and the basis from which they can begin to construct a model that explains the visual and physical relationships among earth, sun, moon, and the solar system. Direct observation and satellite data allow students to conclude that earth is a moving, spherical planet, having unique features that distinguish it from other planets in the solar system. From activities with trajectories and orbits and using the earth-sun-moon system as an example, students can develop the understanding that gravity is a ubiquitous force that holds all parts of the solar system together. Energy from the sun transferred by light and other radiation is the primary energy source for processes on earth's surface and in its hydrosphere, atmosphere, and biosphere.

By grades 5-8, students have a clear notion about gravity, the shape of the earth, and the relative positions of the earth, sun, and moon. Nevertheless, more than half of the students will not be able to use these models to explain the phases of the moon, and correct explanations for the seasons will be even more difficult to achieve.

Read the entire National Science Education Standards online for free or register to download the free PDF. The content standards are found in Chapter 6.

Author and Copyright

Kimberly Lightle is Director and resource specialist for the Middle School Portal 2: Math & Science Pathways project.

Please email any comments to msp@msteacher.org.

Connect with colleagues at our social network for middle school math and science teachers at http://msteacher2.org.

Copyright June 2007 - The Ohio State University. Last updated September 19, 2010. This material is based upon work supported by the National Science Foundation under Grant No. 0424671 and since September 1, 2009 Grant No. 0840824. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.