Celebrating the Solstice and Equinox
Cindy Fry, Sandy Kelnhofer, Barbara Quintasket
Paschal Sherman Indian School, Omak, Washington

Grade level
Fourth

Time required
Six 60-minute class periods

Materials
The Colville story, “Winter Months”
Okanogan Salish words for months
Okanogan Salish words for seasons
“Number of Hours of Daylight” worksheet
Chart paper and markers
World globes or maps
Science journal
NASA’s Winds of Change CD ROM
Poster board and art materials for each student

Goals
By completing this lesson, students will

1. discover that seasonal changes and latitude on Earth affect the number of hours of daylight in each day,
2. gain knowledge of the solstice and equinox,
3. gain knowledge of traditions and rituals surrounding the seasons,
4. listen to a traditional wisdom story and be introduced to the Okanogan Salish words for the months and seasons and
5. develop inquiry process skills.

Science standards addressed
National Science Standards

• Abilities necessary to do scientific inquiry
• Objects in the sky
• Changes in Earth and sky
• Understanding about science and technology

American Indian Science Standards

• Changes in Earth’s surface, weather fluctuations and movements of celestial objects and how they affected historical American Indian community locations, annual migrations, and agricultural and ceremonial cycles

Teacher tips
Invite and elder to tell the Colville story, “Winter Months”, or learn it yourself, it so it can be told rather than read, in keeping with oral tradition.

Students should have some prior knowledge of what causes the seasons. One means of demonstrating this is by using an Earth globe with a flashlight to simulate the Sun. Show students how the tilt of Earth remains the same as Earth moves in its annual orbit, but the angle of Sunlight hitting Earth changes throughout the year.

Bookmark the web sites prior to the lesson for quick access during the lesson.

Background information
The seasons occur because the tilt of Earth's axis never changes while Earth orbits around the Sun. The north end of Earth’s axis always points in the same direction, almost directly to the North Star. About June 21st, the North Pole is tilted toward the Sun, so that the Sun’s rays strike the Northern hemisphere at a more direct angle. The more direct the angle, the more concentrated the Sun’s radiance. About December 21st, the North Pole is tilted away from the Sun, so that its rays strike the Northern hemisphere at a more oblique angle. These two dates are also known as the summer and winter solstice, and they mark the beginning of the summer and winter seasons in the Northern hemisphere. Each season lasts about three months and brings changes in temperature, weather and the length of daylight.

Summer solstice: In the Northern hemisphere, this day has the longest daylight hours of the year and is the first day of summer. It occurs on or about June 21st. The Sun reaches its most northernly point, directly over the Tropic of Cancer (23º 27’ north latitude).
Winter solstice: In the Northern hemisphere, this day has the shortest daylight hours of the year and is the first day of winter. It occurs on or about December 21st. The Sun reaches its most southernly point, directly over the Tropic of Capricorn (23º 27’ south latitude).
Equinox: Comes from a Latin word meaning "equal night." The time when night and day hours are of almost equal length on all parts of Earth. The Sun crosses directly over Earth’s equator.
Spring equinox: The beginning of spring, often called the vernal equinox. It occurs on March 20th or 21st.
Autumnal equinox: The beginning of autumn. It occurs on September 22nd or 23rd.

For further information about what causes the seasons, visit the NASA Kids web page.

Procedure
Engagement

1. Invite an elder to tell the wisdom story, “Winter Months” using the Salish words for each month and season. Post the words in the classroom. Discuss the story.
2. List the following questions on a chart and record student ideas.
   • What month has the longest daylight hours in the Northern Hemisphere?
   • What month has the shortest daylight hours?
   • Is there any time in the year where light and dark hours are equal?
   • Are these days the same length everywhere in the world?

Exploration

1. Working in small groups, have students use a map or atlas to determine the latitude and longitude of the local area. Students should then use the Internet to determine the time of sunset and sunrise for the date at that location. (One suggested site is the Complete Sun and Moon Data for One Day – see Resources section). Discuss students’ findings.
2. Have students repeat this procedure for the 21st day of each month, recording the data in the data sheet.
3. Have half the groups repeat the data collection for 70 degrees north latitude (Northern Alaska) and the other half for 0 degrees latitude.

Explanation

1. Have student groups share their results by writing them on a class chart similar to their data sheet, and graphing the data on a large class graph. Ask students to work with their groups to look for patterns. Discuss together.
2. Students should work with their groups to hypothesize about what causes the pattern of changes in daylight hours they observe, then write their hypotheses in their science journals. Share hypotheses and discuss.
3. Access NASA’s Winds of Change CD ROM Movie “Why do the Seasons Occur?” or go to the NASA Kids site to view a short movie called “Earth’s Seasons”. With student input, develop definitions of solstice and equinox and write them on the chart.

Elaboration

1. Access the Earth and Moon Viewer web site to view seasonal changes in daylight hours. This site provides views of Earth and Moon from several perspectives for any time of the year, and so can be used to illustrate the concepts just learned.
2. Working with partners or on their own, have students research the rituals and traditions of one season. Encourage them to research a variety of time periods and places in the world. Have students make a creative poster of findings. Ask them to emphasize how each event is tied to the season.

Evaluation

1. Assess student understanding of the concepts through review of their written and oral hypotheses.
2. Assess students’ use of process skills by observing and reviewing their work, especially their data collection and graphing.
3. Use the Earth and Moon Viewir site to assess students’ abilities to apply the concepts. Ask them to predict what the Earth view would be for a specific date, or alternatively, to predict what season you are showing them from the site.

Follow up activities

1. Invite several elders and students’ families to share the celebrations of winter and summer, spring and fall. Encourage comparisons of ideas. Make this a family event that includes foods used to celebrate the season.
2. Use the lesson on seasons at NASA’s Thursday’s Classroom site with students to reinforce the concepts learned in this lesson.

Resources
Web sites

NASA Kids – Provides explanation of seasonal changes
http://kids.msfc.nasa.gov/News/1999/News-equinox.asp

NASA Kids: Earth’s Seasons – Contains a short video clip that shows the causes of changes in the seasons
http://kids.msfc.nasa.gov/earth/seasons/EarthSeasons.asp

US Naval Observatory’s Complete Sun and Moon Data for One Day – Provides sunset and sunrise times for any day
http://aa.usno.navy.mil/data/docs/RS_OneDay.html#forma

Earth and Moon Viewer – Shows views of Earth and Moon for any day and time
www.fourmilab.ch/cgi-bin/uncgi/Earth

NASA’s Thursday’s Classroom – This site has lessons that reinforce the concept of why we have seasons
www.ThursdaysClassroom.com

Winds of Change CD – Contains a variety of excellent images and activities. Can be obtained free from a NASA Educational Resource Center, or ordered electronically by sending a message to pcfalcon@mail1.jpl.nasa.gov
http://winds.jpl.nasa.gov/education/index.html