““A Globe Walk”A Globe Walk”Modeling the Modeling the

““Reasons for the Seasons”Reasons for the Seasons”

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

A Class of EventsA Class of Events• Earth Rotates on Its AxisEarth Rotates on Its Axis• Earth is Tilted on its AxisEarth is Tilted on its Axis• Earth’s Revolves in an Orbit around the SunEarth’s Revolves in an Orbit around the Sun• Earth’s Orbital Radius is Constantly Earth’s Orbital Radius is Constantly

Changing.Changing.• The Lengths of Daytimes Gradually Change The Lengths of Daytimes Gradually Change

as the Seasons Change.as the Seasons Change.• The Altitudes of the Sun Gradually Change The Altitudes of the Sun Gradually Change

during a Day and as the Seasons Change.during a Day and as the Seasons Change.• Seasonal changes are most dramatic in the Seasonal changes are most dramatic in the

Polar Regions.Polar Regions.

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

http://www.eoearth.org/article/Earth-Sun_relationships_and_insolation

Students are probably less aware of Students are probably less aware of seasonal changes in the “altitude” of the sun.seasonal changes in the “altitude” of the sun.

Today, the “midday” altitude of the sun in Kotzebue, Today, the “midday” altitude of the sun in Kotzebue, Alaska is 44.8Alaska is 44.8º at 1:55 PM Alaska Standard Time.º at 1:55 PM Alaska Standard Time.

The Distant HorizonThe Distant Horizon

A U.S. Naval Observatory web site provides A U.S. Naval Observatory web site provides the sun’s altitude on any day at any Latitudethe sun’s altitude on any day at any Latitude

.. http://www.usno.navy.mil/USNO/astronomical-applications/data-services/alt-az-us

Kotzebue, Alaska is located 33 miles north of the Arctic Circle

You can learn more about Kotzebue You can learn more about Kotzebue by visiting their web siteby visiting their web site.

http://kotzpdweb.tripod.com/city/index.html

Today, the “midday” altitude of the sun in Amherst is Today, the “midday” altitude of the sun in Amherst is 69.469.4º at 11:50 AM Eastern Standard Timeº at 11:50 AM Eastern Standard Time.

The Distant HorizonThe Distant Horizon

A U.S. Naval Observatory web site provides A U.S. Naval Observatory web site provides the sun’s altitude on any day at any Latitudethe sun’s altitude on any day at any Latitude

.. http://www.usno.navy.mil/USNO/astronomical-applications/data-services/alt-az-us

Diagrams have limited value illustrating Diagrams have limited value illustrating seasonal changes in the altitude of the sun seasonal changes in the altitude of the sun

and lengths of daytimeand lengths of daytime

http://okfirst.mesonet.org/train/meteorology/Seasons.html

Animations can more effectively reveal Animations can more effectively reveal aspects of seasonal changes aspects of seasonal changes

such as the lengths of daytimes such as the lengths of daytimes in the Polar Regionsin the Polar Regions..

http://esminfo.prenhall.com/science/geoanimations/animations/01_EarthSun_E2.html

http://www.cs.sbcc.cc.ca.us/~physics/flash/LengthofDay.swf

The Globe WalkThe Globe Walk

A classroom, a model of the sun, a A classroom, a model of the sun, a model of Earth, a representation of model of Earth, a representation of Earth’s orbit, two straws, and a Earth’s orbit, two straws, and a protractor can be used to demonstrate protractor can be used to demonstrate a variety of daily and seasonal a variety of daily and seasonal changes.changes.

A Demonstration ofA Demonstration ofSolstices and EquinoxesSolstices and Equinoxes

The 2010 Astronomical Seasons The 2010 Astronomical Seasons (for the Northern Hemisphere)(for the Northern Hemisphere)

Spring began at 12:32 PM EST on March 20Spring began at 12:32 PM EST on March 20thth

Summer began at 6:28 AM EST on June 21Summer began at 6:28 AM EST on June 21stst

Autumn will begin at 10:09 EST on September 21Autumn will begin at 10:09 EST on September 21stst\\

Winter will begin at 6:38 PM EST on December 21Winter will begin at 6:38 PM EST on December 21stst

Other Globe Walk Other Globe Walk Demonstrations Include:Demonstrations Include:

• Changes in the altitude of the sun at Changes in the altitude of the sun at different Latitudes as the seasons different Latitudes as the seasons change.change.

• Changes in the Lengths of Daytimes at Changes in the Lengths of Daytimes at different Latitudes as the seasons different Latitudes as the seasons change.change.

• Summer Solstice at the North Pole.Summer Solstice at the North Pole.

• Daily changes in the Altitude of the Sun.Daily changes in the Altitude of the Sun.