The main idea of these lessons is to gather empirical evidence that shatters the misconception many students (non-students too) hold that when we are closer to the Sun it is summer and when we are farther away from the Sun it is winter. Or they know the tilt causes the seasons but they believe it’s because the tilt brings one hemisphere closer to the sun and that is why one hemisphere has summer while the other has winter. Hopefully, by the end of these lessons students are convinced by evidence that Earth’s varying distance to the Sun DOES NOT cause the seasons. Then we move on in this unit to finding out what DOES cause the seasons.
Lesson 1 (3 class periods):
Use Proportional Reasoning to Develop a Scale Model of Earth’s Orbit Around the Sun:
Students learn that scientists use models to demonstrate ideas, explain observations, and make predictions. They develop and use a scale model to construct an explanation that Earth travels around the sun in a nearly circular orbit and that the Sun is very close to the center of Earth’s Orbit. But why does the orbit look more elliptical in models we see in our text books like this one:
One of the reasons is that this is not a scale model and it is a side view. In this lesson, we use proportional reasoning to create and analyze a top-down scaled model of Earth’s orbit. This shows the students that Earth’s orbit is almost a perfect circle–so we never get that much closer or farther from the Sun throughout the year. (They also find out that we are closest to the Sun in January and farthest from the Sun in July—that really blows their minds!) But why does the side view model LOOK like it’s elliptical. I show them this:
We discuss the strengths and weaknesses of a non-scaled, side view model of Earth’s orbit compared to a scaled, top-down view of Earth’s orbit.
Lesson 2 (2 class periods):
Construct, Analyze, and Interpret Graphical Displays of the Monthly Average Temperature Patterns of a Northern Hemisphere City, Southern Hemisphere City, and an Equatorial City to Provide Evidence that Supports or Refutes Whether Changes in Earth’s Distance to the Sun Causes the Seasons.
Students graph the average monthly temperature of a Northern Hemisphere, Southern Hemisphere, and Equatorial City. Then, they analyze the graph for patterns and summarize these patterns. We also check out http://www.worldweatheronline.com/chicago-weather-averages/illinois/us.aspx. I write a city in the search box. When I get to the city information, I look to the icons on the left and click on the one that is a bar graph. This sends me to a line graph of the monthly temperature patterns (scroll down a bit to find it). I ask students to select cities from around the world so we can see if their temperature change patterns match the patterns we graphed and the observations we summarized. Most cities will. Some will not if they are located in mountainous places but this brings up interesting discussion points. Some patterns we observe are: Places in the Northern Hemisphere tend to be warmer in the months of June, July, and August and colder in December, January, and February. The opposite pattern is observed in the Southern Hemisphere. The temperature of places near the Equator (in the Tropics) does not vary a great deal. The farther a place is from the Equator, the greater the variation in temperature at that place over the course of the year tends to be. Places near the Equator (in the Tropics) tend to be warmer than other places on Earth. The farther a place is from the Equator, the colder the place tends to be.
How does this fit in to our Essential Question: Does How Far Away the Earth is From the Sun Cause the seasons? Well, if distance caused the seasons, than every place on Earth would have the same temperature patterns at the same time.
Lesson 3 (2-3 class periods):
Use Proportional Reasoning to Develop a 3D Scale Model that Compares the Size of Earth to the Sun and the Distance Between Them. Analyze this model to determine if the tilt brings one end of the Earth significantly closer to the Sun to cause seasonal temperature patterns. Write a persuasive essay, using the CER model (Claims, Evidence, Reasoning) to convince people (using evidence) that the Earth’s changing distance to the Sun is NOT what causes the seasons.
These are my favorite resources for showing other scales of Earth compared to other parts of the solar system. The students enjoy watching them and we discuss how scaling lets us understand concepts by looking at things with a different perspective.
- This video that scales the earth to other stars. (Rigel is the brightest star in Orion); VY Canis Majoris is one of the largest known stars in the Milky Way http://www.youtube.com/watch?v=c8CgDGhYKe8
- This is a scale picture of the sun/earth http://blogs.discovermagazine.com/imageo/2015/02/24/cure-for-hubris/#.VyjKNjArLIX http://www.universetoday.com/65356/how-many-earths-can-fit-in-the-sun/
- Time lapse video of the Sun https://www.youtube.com/watch?v=8MImmQvqCSg and then a scale of earth next to a solar flare. http://www.nasa.gov/mission_pages/sunearth/news/gallery/earth-scale.html
- What North America would look like on other planets http://www.huffingtonpost.com/2014/11/09/north-america-on-other-planets_n_6117222.html
- Image of the Sun and planets of our solar system to scale. http://imgur.com/fjoPcBW
- Earthrise from the moon http://www.planetary.org/blogs/emily-lakdawalla/2014/05130951-a-new-earthrise-over-the-moon.html?referrer=http://t.co/hNGYjsCbJo
- Earth view from Saturn: http://www.jpl.nasa.gov/news/news.php?release=2013-229#1
- Earth view from Mars: http://www.jpl.nasa.gov/news/news.php?release=2014-039
- If the Sun were the size of a basketball: https://www.youtube.com/watch?v=ke_3rOrny-g&feature=youtu.be&list=PL_qffRVV3oS2KM9teLoJ8K5woiFdcaudD
- How Big is the Solar System from It’s Okay to Be Smart: https://www.youtube.com/watch?v=_mD-ia6ng0A
- If the moon were one pixel http://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html
These lessons are found on TeachersPayTeachers
Materials needed for lesson 1, 3**:
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