Standards Database Logo
Home | Browse | Search | Purpose | History | Process | Acknowledgment| Reference

 


 

McREL Standards Activity


Earthly Phenomena: Finding the Answers


Purpose:As a result of this activity, students will be able to explain how the position and motion of the Earth and Moon, relative to the Sun, explain phenomena on Earth.
Related Standard & Benchmarks:
Science
 Standard 1.Understands atmospheric processes and the water cycle
   Level III [Grade 6-8]
   Benchmark 5. Knows how the tilt of the Earth’s axis and the Earth’s revolution around the Sun affect seasons and weather patterns (i.e., heat falls more intensely on one part or another of the Earth’s surface during its revolution around the Sun)
Science
 Standard 3.Understands the composition and structure of the universe and the Earth's place in it
   Level III [Grade 6-8]
   Benchmark 2. Knows how the regular and predictable motions of the Earth and Moon explain phenomena on Earth (e.g., the day, the year, phases of the Moon, eclipses, tides, shadows)
Student Product:Worksheet
Material & Resources:
Paper sacks for each group of 3-4 students containing the following items:

  • flashlight
  • small styrofoam ball
  • larger styrofoam ball with a wooden stick inserted through its center; for the stick, bamboo skewers or chop sticks (available in grocery stores) work best, but a pencil would also do
  • permanent marker or rubber band
  • round-headed straight pins



Worksheet (incorporated into "Activity" below)


*This activity requires that the room be darkened enough to see the shadow cast by a flashlight.
Teacher's Note:While this is a lengthy activity, it can easily be separated into several tasks that can be taught during different class periods (see Activity).
Activity
Every day around the world, the Sun rises in the East and sets in the West; every month the Moon methodically passes through its different phases; and every year the seasons predictably come and go.  However, without a model, it is difficult to visualize how the motions of the Moon and Earth, relative to the Sun, create these commonplace phenomena.  In this activity, we will use a simple model to demonstrate these and other phenomena quite clearly.

Students should work in groups of 3-4.  Each group should have a separate worksheet for each person and a single paper sack containing the following items:

  • a flashlight (the Sun),
  • a small styrofoam ball (the Moon),
  • a larger styrofoam ball with a stick running through its center (the Earth and its axis),
  • a permanent marker or rubber band (for the Earth’s equator), and
  • straight pins with round heads.

Working as a group, use these items to perform the following tasks; answer the worksheet questions independently.


Task 1: Demonstrating Night and Day in Different Parts of the World

Turn the lights in the classroom off.  Hold the flashlight (Sun) a few feet away from the larger styrofoam ball (Earth).  Position "Earth" so that its axis is roughly vertical and tipped out slightly.  The area of "Earth" being illuminated by the "Sun" is now experiencing daylight.  Use your model to answer the following questions.


  1. Is there a part of the "Earth" not currently being illuminated by the "Sun?"  Explain your answer.
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

Now slowly spin the "Earth" on its axis (i.e., use the stick to spin the styrofoam ball around) to simulate the Earth’s rotation and the day and night cycle.


  1. What happens to the side of the "Earth" that was previously illuminated?
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

  2. What happens at the polar regions?
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

Hold the "Earth" still again and look at the edges of the area illuminated by the "Sun."


  1. Do they appear to be receiving the same amount of light as the area of "Earth" that is directly illuminated by the light from the "Sun?"  Explain your answer and relate it to the day and night cycle.
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________


Task 2: Demonstrating the Seasons on Earth

Earth’s seasons occur because the Earth is inclined about 23.5° on its axis.  As a result, during its orbit around the Sun, different parts of the Earth receive more sunlight during certain times of the year and less during others.

The summer solstice (the first day of summer and the longest day of the year) occurs for each of the Earth’s hemispheres when the Sun’s zenith is at its highest point in the sky for the year, as viewed from Earth (in the northern hemisphere, this is when the Sun appears the farthest north in our sky for the entire year).  The winter solstice (the first day of winter and the shortest day of the year) occurs for each of the Earth’s hemispheres when the Sun’s zenith is at its lowest point in the sky for the entire year.  (That is, the Sun is directly in line with the Tropics of Cancer and Capricorn; for a person standing on a tropical latitude, the Sun would appear directly overhead at noon on the respective solstice.)

An equinox occurs twice a year, when the Sun is directly in line with the Earth’s equator.  In the northern hemisphere, the autumnal equinox (the first day of autumn) occurs when the Sun appears to travel across the equator from north to south, and the vernal equinox (the first day of spring) occurs when the Sun appears to travel across the equator from south to north.  The situation is reversed in the southern hemisphere (i.e., while the northern hemisphere is experiencing summer, the southern hemisphere is experiencing winter).  On these days, the number of hours of daylight equals the number of hours of darkness.

These concepts can be clarified using your model.  Draw a line using the permanent marker or place the rubber band around the "Earth," half-way between the poles, to represent the equator.  The upper half will represent the northern hemisphere and the lower half will represent the southern hemisphere.  While one student operates the flashlight (Sun), another student should tilt and spin the "Earth" on its axis and walk around the "Sun" to simulate the Earth’s year-long orbit; in doing this, it is important that the student carrying "Earth" keeps the axis tilted in the same direction at all times (e.g., keep the tilt toward a particular corner or object in the room).  Since the flashlight only shines in one direction, unlike the real Sun which shines in all directions, the student operating the model Sun will need to turn the flashlight so that it always shines on the "Earth."  Use your model to answer the following questions.


  1. As the "Earth" makes its orbit around the "Sun," explain how the "Sun’s" light, and hence heat, falls differently on the "Earth" at different points in its orbit.
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

  2. Based on your answer to #5, explain how the Earth’s position and motion relative to the Sun create the four seasons on Earth.
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

  3. Describe what happens at the polar regions (refer to your answer to #3).
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________


Task 3: Demonstrating the Phases of the Moon and Solar and Lunar Eclipses

You have probably noticed that, from our vantage point on Earth, the Moon’s appearance goes through a cycle of changes every month.  You likely have heard terms such as "full moon" and "new moon," but what causes the Moon to go through this cycle?  You may have also witnessed a solar or lunar eclipse, in which the Sun or Moon appear dark for a short period of time, as viewed from a certain location on Earth.  Once again, your model can be used to clarify the causes of these phenomena.

To do this, first press one of the round-headed stick pins into the model Earth.  This will represent your vantage point from Earth as you observe the Moon.  Then turn the lights in the classroom OFF.  As one student shines the flashlight (Sun), the student operating the "Moon" can begin orbiting "Earth;" the "Moon’s" orbit should be tipped slightly relative to the plane of the "Earth’s" orbit around the "Sun."  [Note:  The tilt of the Moon’s orbital plane is about 5° with respect to the Earth’s orbital plane.  This allows for half of the Moon’s surface to always be lighted by the Sun (except during a lunar eclipse), and is the reason why eclipses do not occur regularly twice every month as the Moon circles Earth.]

Watch as the illuminated portion of the Moon changes (from your stick pin’s vantage point on Earth) as the "Earth" rotates on its axis and as the "Moon" makes its orbit around the "Earth."  When doing this, keep in mind when day and night are occurring from your vantage point on Earth.  This will affect your view of the Moon.


  1. What causes the phases of the Moon?
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

Now, position the "Moon" directly between the "Earth" and the "Sun."


  1. Why do you think this is called a "solar eclipse?"
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

Finally, position the "Earth" directly between the "Sun" and the "Moon."


  1. Why do you think this is called a "lunar eclipse?"
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

*Note:  The eclipses you see with the model are inaccurate in size due to the size of styrofoam balls and distances used.


Task 4: Demonstrating Shadows on Earth

Certainly you have noticed that the size and shape of your own shadow change as the day progresses.  However, have you ever thought about why your shadow changes?  And have you ever considered how your shadow might appear at the same moment in a different location on Earth?  Your model will help to answer these questions.

Stick a few more stick pins into the Earth model at different locations in the northern and southern hemispheres.  As one student shines the flashlight (Sun) on the "Earth," look at the shadows cast by the different stick pins.  Rotate the Earth on its axis and move it slowly through its orbit as you watch the shadows cast by the stick pins.


  1. How does a fixed object’s shadow change through the course of a day?  Explain the cause of this.
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

  2. How are shadows (i.e., those cast by the "Sun") in the southern hemisphere of the "Earth" different from those in the northern hemisphere?  Explain the cause of these differences.
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________

  3. How do shadows on "Earth" vary as the "Earth" goes through different seasons during its orbit around the "Sun?"  Explain.
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________
    ____________________________________________________________________________________________