1. “Reasons for the Seasons”
“A Globe Walk”
Modeling the
“Reasons for the Seasons”

2. “Models are tentative schemes or structures that correspond to real objects, events, or classes of events, and that have explanatory power…….” The National Science Education Standards (Page 117); National Academy Press 1998.

3. A Class of Events Earth Rotates on Its Axis
Earth is Tilted on its Axis
Earth’s Revolves in an Orbit around the Sun
Earth’s Orbital Radius is Constantly Changing.
The Lengths of Daytimes Gradually Change as the Seasons Change.
The Altitudes of the Sun Gradually Change during a Day and as the Seasons Change.
Seasonal changes are most dramatic in the Polar Regions.

4. Most students are aware of seasonal changes in lengths of daytime but may not know that they depend on Latitude.

5. Students are probably less aware of seasonal changes in the “altitude” of the sun.
Today, the “midday” altitude of the sun in Kotzebue, Alaska is 44.8º at 1:55 PM Alaska Standard Time.
The Distant Horizon
A U.S. Naval Observatory web site provides
the sun’s altitude on any day at any Latitude .

6. Kotzebue, Alaska is located 33 miles north of the Arctic Circle
You can learn more about Kotzebue by visiting their web site.

7. Today, the “midday” altitude of the sun in Amherst is 69
Today, the “midday” altitude of the sun in Amherst is 69.4º at 11:50 AM Eastern Standard Time.
The Distant Horizon
A U.S. Naval Observatory web site provides
the sun’s altitude on any day at any Latitude .

8. Diagrams have limited value illustrating seasonal changes in the altitude of the sun and lengths of daytime
Demonstrate the “Walk the Globe” activity and make the connection to the Albedo and Angle of Incidence activity that teaches would have done prior to this PowerPoint.

9. Animations can more effectively reveal aspects of seasonal changes such as the lengths of daytimes in the Polar Regions.

10. The Globe Walk
A classroom, a model of the sun, a model of Earth, a representation of Earth’s orbit, two straws, and a protractor can be used to demonstrate a variety of daily and seasonal changes.
Do the Globe Walk demonstration at this point.

11. A Demonstration of Solstices and Equinoxes
The 2010 Astronomical Seasons (for the Northern Hemisphere)
Spring began at 12:32 PM EST on March 20th
Summer began at 6:28 AM EST on June 21st
Autumn will begin at 10:09 EST on September 21st\
Winter will begin at 6:38 PM EST on December 21st

12. Other Globe Walk Demonstrations Include:
Changes in the altitude of the sun at different Latitudes as the seasons change.
Changes in the Lengths of Daytimes at different Latitudes as the seasons change.
Summer Solstice at the North Pole.
Daily changes in the Altitude of the Sun.