4-7 Lesson 1

Sunrise...Sunset - Bilingual Telemation Unit

4-7 Lesson 1:
The Shadow Knows...

Background:

Many ancient societies have traced shadows cast by a gnomon (a stick that cast a shadow) to predict the time, seasons and moreover a calendar for planting so that natural rhythms were useful for life in their culture. These were the first sundials. The position of the sun in the sky and the length of time the sun appears in the sky create the daily pattern and the seasonal pattern of sunlight. The sun does not always rise and set in exactly the same places. In summer the sun rises to the north of east and sets to the north of west. At noon it is high in the sky. In winter the sun rises to the south of east and sets to the south of west, and does not rise very high in the sky at noon. Days are longer in summer than in winter as the sun travels a longer path above the horizon. This variation is due to the earth's axis tilt as it orbits the sun. This tilt is the main cause of the climatic changes of the seasons.

Concepts:

Every day, the sun rises somewher on the eastern horizon, moves higher until about noon, and then moves lower until it sets somewhere on the western horizon. In autumn, the daylight period grows gradually shorter, becoming shortest about the time of winter solstice (December 21). Then it grows longer, becoming longest about the time of the summer solstice (June 21). Seasons are caused by the tilt of the earth's axis.

The Scientific Investigation:

Can you find a pattern in the sun's path of travel across the sky over time? What can be discovered when a shadow is marked and studied daily?

Purpose:

This activity is structured to observe shadows as an indication that the sun's rays hit the earth at different angles during a day and over time. Students will be able to identify and predict the pattern the sun takes as it travels across the horizon and telecommunicate and compare their findings with other students.

Objectives:

Students will:

Observe and log information about the sunrise and sunset.

Use the metric system to measure shadows.

Chart and compare observed data by creating graphs and tables.

Analyze data to infer solar/seasonal patterns.

Telecommunicate with other students at different latitude locations to relate and compare the shadow's pattern as the sun's rays hit the earth over time.

Materials:

(for each group)

Meter stick

Board

Chalk or patio paint

Science journals

Graph paper

Compass

Procedures:

Collaborative Group Activities

Location: Students in small groups will find an undisturbed area outside at school to plot and paint shadows. They will need to make sure that this location gets direct sunlight.
Construction of the gnomon: Each group of students will build a gnomon. It is their choice as how to build and decorate their gnomon, then place on a stand. The requirements are that each gnomon measure a meter in height to include the height of the stand. The stand will sit level on the ground with the gnomon stick perpendicular to its stand in a vertical position.
Taking measurements: Daily at recess, lunch, and after school, cooperative groups of students will place their gnomons in their designated place. First, determine due north using a compass. Second, place the protractor at the base of the gnomon so that the 90 degree mark is pointing north. Observe the shadow of the gnomon and trace it with chalk: then paint with patio paint. When dry, mark the end of the shadow, date and time it with permanent marker. Measure the length in centimeters. Record these measurements into student science journals. Journal entries should include all student observations and questions for further investigation. Each group will create a chart/graph to share their information with the class.
Making predictions: After the first day of observing shadow lengths, students will make predictions to suggest what pattern the shadow will take over time. Use a question sheet to encourage observations.
Sample questions:
1. What direction does the shadow point in early morning? at noon? just before the sun sets? (You may use your compass.)
2. Will there be a time when the sun is overhead? What kind of shadow will you see?
3. Will the shadow get longer, shorter, or remain the same length?
4. What can you tell about the sun's position in the sky by looking at the shadows?
(Journal entries with predictions will be used to compare with direct observations at a later time.)
Daily observations: For the next eight weeks, students will measure, paint, and record the length of the gnomon's shadow at noon ("noon" is about 1:00 PM on Daylight Savings Time). Students will write about their observations, predictions and describe the pattern that is occurring as journal entries to include student-created tables and graphs to display results. Does the tip of the shadow form a pattern? In which direction do you think this pattern will proceed? Why?
These charts should include: date, time, lengths of shadow.
Student groups will read and share stories about ancient peoples' use of gnomons and other time recording instruments.

Telecommunication:

Groups will telecommunicate their scientific investigations as follows:

Teacher's Name
School
City, State, latitude in degrees and minutes
Time of day when shadows were measured
Dates
Lengths of shadow in centimeters
Any questions and comments about the investigation.

Part 2: My Personal View of Sunrise/Sunset

Record sunrise/sunset times: Students observe sunrise and sunset daily for a given period and mark the time as a homework investigation. The place that the observation is done must be the same for each observation. Students graph the hours of daylight and darkness. Does the sun rise and set in the same spot daily? If not, what do you think causes this shift? Is there a pattern occurring?
Each student in a group will include in his/her journal a description of his/her personal view of the sunrise and sunset. The student will sketch what is seen (buildings, trees, smoke stacks etc.) at sunrise and sunset.
Using their sketch and what they see, they will write a description in their journal of their view. Along with the sketch, students will be encouraged to write three words to express how they felt when watching the sunrise/sunset scene. These descriptive feelings will be shared with their group at school.
Groups can write poems to share on-line along with their recorded data.

Part 3: Gathering Newspaper Data

Teacher will assign designated students the task of daily newspaper collection for sunrise and sunset times in their location.

Students will graph observed hours of daylight/darkness and the newspaper's hours of daylight/darkness.

This information will be compared and shared on-line. See directions below. (Observed data may reflect students' view from where they observe the sunrise/sunset.)

The hours of daylight and darkness will be shared on-line as follows:
1. Teacher's name
2. School name
3. City, State, latitude in degrees and minutes
4. Dates
5. Times sunrise and sunset were observed
6. Newspaper times for that date
7. Hours of daylight and darkness
Conclusion:

What did you learn about the lengths of the gnomon's shadow over a day? Over a period of time? What did you discover about the differences in shadow lengths through the seasons (if measurements were taken over the year)? Why are there differences in shadow length?

Assessment:
As a form of assessment student groups will share their predictions and actual gathered data with other groups in their class through graphs and charts.

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