Fall Ongoing. Measuring Sun Position: Yearly Change

Transcription

1 Measuring Sun Position: Yearly Change Edible Schoolyard Pittsburgh Fall Ongoing MATERIALS 1 piece of steel rebar (approx. 4 feet tall and ½-inch diameter) Rubber hammer Bright tape or flags Measuring tape Garden journals PREPARATION At the start of the school year, find a suitable spot in the garden for a sun position measurement station. The spot should receive plenty of sunlight and be unobstructed by shadows from trees or buildings. Additionally, make sure the spot is surrounded with a flat measuring surface that is uninterrupted by garden structures. PROCEDURE Step 1: Establish a permanent sun position measurement station (school start) Insert the upright piece of steel rebar about 6 inches into the ground. Use a rubber mallet to hammer the pole approximately 1 foot into the ground, or until it is solid and secure. Use bright tape or flags to label the station. Make sure the upright rebar is clearly visible in order to prevent any tripping accidents. Alternately: If the garden lacks a suitable space for a permanent measurement station, identify an alternate spot outside of the garden for a non-permanent measurement station. Insert a yardstick into a coffee can filled with soil or stones. Use a tape measurer to take shadow measurements. Record data and return the yardstick to a safe spot in the garden. Repeat the same process during consecutive lessons. Step 2: Take weekly shadow measurements throughout the growing season (ongoing) Take measurements at the same time of day. Schedule garden sessions during a set day and time each week to guarantee accurate measurement data. Use a tape measurer to measure the length of the upright rebar s shadow. Measure from the base of the rebar to the tip of the shadow. Have students the time measurement was taken and length of shadow in their garden journals. Repeat the same process during consecutive garden lessons. Step 3: Compile and analyze measurement data (late fall) In the classroom: Split students into groups and assign each group a month of the year during which sun position measurements were taken. Pass out garden journals and have students consult the measurement data for their assigned months. Distribute large pieces of paper to each group. Instruct students divide the paper in half and make two columns date and time measurement was taken and length of shadow. In the meantime, take out a piece of flip chart paper and do the same. Have students record their month s measurement data on the paper. When they re finished, have students share their measurements. Compile the entire class data on the flip chart paper. Transition to discussion.

2 Measuring Sun Position (Year) Patterns & Preparation OBJECTIVES ENGAGE Discuss the following questions as a group: What trends do you notice in the data? What has happened to the measurements since the start of the school year? What could account for the differences in shadow length? Based on your measurements, is the sun getting higher or lower on the horizon over time? Students will be able to describe how the sun moves in the sky over the course of a year Students will be able to describe the relationship between the angle of the sun and the seasons EXPLAIN How does the sun move across the sky during one year? The sun warms the earth most intensely on the first day of summer, or what we commonly call the Summer Solstice. On this day, the sun is at its highest point in the sky and its light is hitting the earth most directly. From the summer solstice onwards, the sun slowly moves toward the southern horizon as winter approaches. The first day of winter is marked by the Winter Solstice. On this day, the sun is at its lowest point in the sky. From the Winter Solstice onwards, the sun begins to climb above the horizon until the Summer Solstice arrives once again. If you were to look at the place of the sun in the sky every day at noon, you would notice the subtle changes in the sun s position. However, looking directly at the sun, even for a moment, can cause blindness! Instead, we measure the length of the shadow that the sun casts. By measuring the length of the shadow at the same time of day, we can track the sun s position in the sky over the course of a year. What is the relationship between the angle of the sun and the seasons? As stated before, the Summer Solstice marks the time when the sun is highest in the sky. During this time, the sun s rays are hitting the earth most directly. The direct light from the sun produces heat and, in turn, consistently hot weather conditions (summer). As the sun slowly lowers towards the horizon, the light is not as intense and the weather starts to get cooler (fall). The arrival of the Winter Solstice marks the time when the sun is the lowest on the horizon. During this time, the light is not hitting the earth very directly. The weak, indirect sunlight creates colder weather conditions (winter). After the Winter Solstice, the sun begins to slowly climb above the horizon. Over time, the sunlight becomes more direct and the weather gets warmer (spring). The sun continues to climb until it reaches its highest point in the sky. The Summer Solstice has arrived once again, completing the cycle. ADDITIONAL CONTENT INTEGRATION (see previous page) Use a piece of string to attach an inflatable globe to the ceiling. Mark your location on the globe with a piece of bright tape. Use a flashlight to illustrate the relationship between the angle of the sun and the changing of the seasons. Additional Materials Flashlight Inflatable globe String Bright tape EVALUATE Journal prompt: What are the weather characteristics of your favorite season?

3 Charting Seasonal Change Sun Angle Chart (3 Pole) Length Angle (inches) (degrees)

4 Measuring Sun (Day) Edible Schoolyard Pittsburgh Fall October MATERIALS Yardstick Coffee Can Stones or soil Measuring tape Garden journals Outdoor thermometer Optional: compass PREPARATION Check the weekly weather forecast and schedule this lesson on a mostly sunny day. Scout out a spot in the garden or on the school grounds where you can safely place an upright yardstick for the duration of the school day. Find suitable times during the day of the lesson to schedule 3 4 shadow measurement breaks PROCEDURE Step 1: Tour the garden and make weather observations Gather in the garden shortly after the beginning of the school day. As a group, tour the garden. Have students make observations about the current weather conditions. If students do not normally visit the garden at this time, have them compare morning weather conditions with weather conditions during their normally scheduled garden time. Point out any early morning shadows in the garden. Have students take a moment to examine their surroundings and find additional morning shadow zones. Move the group from sunny spots to shadowy spots. Can you detect a difference in temperature between the two? Step 2: Introduce and explain the purpose of the measurement activity Point out the horizon. The horizon is where the earth meets the sky. Ask students to find where the sun is. Is it high or low on the horizon? Explain how the sun moves across the sky during the course of the day. (Optional: Use a compass to find East and West). Can you guess what will happen to these shadows as the sun gets higher in the sky? We are going to use an upright yardstick to measure the angle of the sun throughout the day. Place the upright yardstick in a coffee can filled with stones or soil. Secure the yardstick so it can stand solidly on its own. The yardstick casts a small shadow as the sun shines down on it. We want to find out how this shadow changes over the course of a day. To do so, we are going to measure the length of this shadow as the sun moves across the sky. We will take 3 measurements over the course of the day. Step 3: Measure the position of the sun throughout the day and collect data Have students take out their garden journals and record time of day the measurement was taken. Next, select a student volunteer to measure the length of the shadow with the tape measurer. Have students record the length in their garden journals. Select another student to take the current temperature reading. Have students record data in their journals. Repeat this process 3 times throughout the day (i.e. morning, lunch, early afternoon, and late afternoon). Save the data for classroom-based analysis.

5 Measuring Sun Position (Day) ENGAGE Pass out garden journals and have students consult their measurement data from the outside activity. Take out a large piece of paper and divide it into three sections. Label the first section Time, the second Shadow Length and the third Temperature. Record the students measurement data in each section. What trends do you notice? How does the length of the shadow change during the day? How does the temperature change? OBJECTIVES Patterns & Preparation Students will be able to explain how the sun moves across the sky over the course of one day Students will be able to describe the relationship between the angle of the sun and temperature EXPLAIN How does the sun move across the sky in one day? As we learned during the outside activity, the horizon is where the earth meets the sky. Over the course of the day, the sun slowly moves from east to west. The sun rises in the east and starts low on the horizon. During the morning, the sun casts long shadows because it is low on the horizon and not hitting the earth very directly. As the sun moves across the sky, it also gets higher above the horizon. The sun is highest in the sky around noon. During this time, the sun s rays are hitting the earth most directly and the shadows decrease in length. As we move into the afternoon, the sun continues to travel across the sky, slowly lowering itself towards the horizon once again. Shadows begin to lengthen again. At the end of the day, the setting sun moves closer to the horizon until it disappears completely. What is the relationship between the angle of the sun and temperature? The sun warms the earth most intensely at noon, when it is most directly hitting earth. When the sun is low in the sky--morning and evening--it is not hitting the earth directly, and its heat is not as intense. Garden plants receive the most intense heat and sunlight during the early afternoon hours. Heat- and sun-loving plants such as tomatoes and peppers thrive under these conditions. Cool-season plants like lettuce, however, prefer a shady spot to hide from the intense heat. Knowing the sun and temperature dynamics of your garden space is important. Thoughtful planning makes for happy garden plants! ADDITIONAL CONTENT INTEGRATION (see previous page) Have students attach upright straws to small squares of cardboard using masking tape. Pass out flashlights and dim the classroom lights. Have students use flashlights to play with different light angles. Similar to our outside experiment, students can notice the difference in shadow length as they change the position of the flashlight. How do you make the longest shadows? How do you make the shadows disappear? EVALUATE Additional Materials Flashlights (1 per student or group of students) Straws Masking tape 4 X 4 cardboard squares Journal prompt: At what time of day was the shadow the longest? When was it shortest?

6 Measuring Sun (Day) Alt. Edible Schoolyard Pittsburgh Spring/Fall Materials Preparation Yardstick Coffee Can Stones or soil Large, flat sheet of cardboard or heavy paper (at least 2 X 3 ) Compass Chalk Marker Measuring tape Check the weekly weather forecast and schedule this lesson on a mostly sunny day. Scout out level spot on school grounds that is unobstructed by trees or buildings. Make sure you can safely place an upright yardstick in this spot for the duration of the school day. Find suitable times during the day of the lesson to schedule hourly shadow measurement breaks PROCEDURE Station Set Up and Procedure: Use a compass to determine North, South, East, and West. Mark the directions with chalk. Place the sheet of cardboard on level ground. Align the edges with the compass directions. Place the upright yardstick in the center of the southern edge of the recording sheet. Mark the direction of magnetic north on the recording sheet. Use chalk to mark the outline of the recording sheet on the pavement. Use marker to outline the coffee can on the recording sheet. (Just in case either one is accidentally moved during the day.) Mark the line and tip of the shadow cast by the yardstick with a marker and record the time that the observation was taken. Throughout the course of the day, periodically (every hour or half hour) record the movement of the shadow of the yardstick by marking the line and tip of the shadow. Optional: Ask students to predict where the shadow will fall after a certain time interval, such as 15 minutes or an hour. Each student or group of students can mark their predictions with a small stone. When the chosen interval has passed, mark the new shadow position with a marker. The class can check their markers against the actual position. Collect data for in-class analysis and discussion. (Alternate measurement activity adapted from