Tracking Time With Shadows

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Objective

SWBAT identify and explain the directional path the sun appears to take as it moves across the sky.

Big Idea

Students observe, measure, and mark the changing position of a shadow. They use the shadow’s changing position to develop an understanding of how Earth’s rotation causes of the sun's apparent motion in the sky and time.

Lesson Overview

5e Lesson Plan Model

Many of my science lessons are based upon and taught using the 5E lesson plan model: Engage, Explore, Explain, Elaborate, and Evaluate. This lesson plan model allows me to incorporate a variety of learning opportunities and strategies for students.  With multiple learning experiences, students can gain new ideas, demonstrate thinking, draw conclusions, develop critical thinking skills, and interact with peers through discussions and hands-on activities.  With each stage in this lesson model, I select strategies that will serve students best for the concepts and content being delivered to them.  These strategies were selected for this lesson to facilitate peer discussions, participation in a group activity, reflective learning practices, and accountability for learning.

Unit Focus  

The Out of This World-A Journey Through Our Solar System unit focuses on students recognizing that Earth is a part of the “solar system” that includes the sun, planets, moons, and stars and is the third planet from the sun. Through models, investigations, graphing, and computer simulations, students learn that Earth revolves around the sun in a year’s time, and rotates on its axis once approximately every 24 hours. They make connections between the rotation of the earth and day/night, and the apparent movement of the sun, moon, and stars across the sky, as well as changes that occur in the observable shape of the moon over a month. The unit wraps up as students learn about the brightness of stars, patterns they create in the sky, and why some stars and constellations can only be seen at certain times of the year.

Lesson Synopsis

This lesson takes place over a two day period.

In the lesson, Tracking Time With Shadows, I begin by covering the clock to bring meaning to our discussion on how people knew what time was before clocks. I introduce the term shadow and students talk about what they know about them and then practice making some with flashlights. This leads to a discussion on how shadows can help identify the time of day and why they change throughout the day. Class moves outside to where students take part in observing, measuring, noting the time, and marking the position of their shadow to develop an understanding of the apparent motion of the sun and the passing of time. Students keep track of the data, then graph it, and analyze it.  They use it as evidence to write an evidence based argument as to why the sun appears to move across the sky.

Next Generation Science Standards  

This lesson will address and support future lessons on the following NGSS Standard(s):

  • 5-ESS1-1: Support an argument that the apparent brightness of the sun and stars is due to their relative distances from Earth.

  

  • 5-ESS1-2: Represent data in graphical displays to reveal patterns of daily changes in length and direction of shadows, day and night, and the seasonal appearance of some stars in the night sky.


  • 5-PS2.1: Support an argument that the gravitational force exerted by Earth on objects is directed down.

 

Scientific & Engineering Practices

Students are engaged in the following scientific and engineering practices

5.) Using Mathematics and Computational Thinking: Student use their shadow lengths and times data and organize them on a line graph to reveal patterns that suggest the sun is moving. They use this graph to construct an evidence based argument that Earth' rotation in relation to the sun's position is what causes the sun to appear to move. 

Crosscutting Concepts

The Tracking Time With Shadows lesson will correlate to other interdisciplinary areas.  These Crosscutting Concepts include:

1.) Patterns: Students use their own shadow models to reveal patterns changes related to time and use these patterns to explain why they repeat daily.

2.) Cause and Effect: Students conduct an investigation to determine the effect of Earth's rotation in relation of the sun's position to explain why the sun appears to move across the sky.

Disciplinary Core Ideas

Disciplinary Core Ideas within this lesson include:

ESS1.A:  The Universe and its Stars

ESS1.B:  Earth and the Solar System

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Classroom Management Considerations

Importance of Modeling to Develop Student

Responsibility, Accountability, and Independence 

Depending upon the time of year, this lesson is taught, teachers should consider modeling how groups should work together; establish group norms for activities, class discussions, and partner talks.  In addition, it is important to model think aloud strategies.  This sets up students to be more expressive and develop thinking skills during an activity.  The first half of the year, I model what group work and/or talks “look like and sound like.”  I intervene the moment students are off task with reminders and redirection.  By the second and last half of the year, I am able to ask students, “Who can give of three reminders for group activities to be successful?” Who can tell us two reminders for partner talks?”  Students take responsibility for becoming successful learners.  Again before teaching this lesson, consider the time of year, it may be necessary to do a lot of front loading to get students to eventually become more independent and transition through the lessons in a timely manner.

 EXPLORE TEAMS (Pre-Set)

For time management purposes, I use “lab rats ” where each student has a number on the back of his or her chair, 1,2,3,4 (students sit in groups of 4)and displayed on the board.  For each activity I use lab rats, I switch up the roles randomly so students are experiencing different task responsibilities which include:  Director, Materials Manager, Reporter, and Technician.  It makes for smooth transitions and efficiency for set up, work, and clean-up.  

Engage

20 minutes

Activating Prior Knowledge:

(For the beginning of this lesson, I cover the clock in the classroom.)  

I begin asking students: "Does anyone know what time it is?" I look to see who glances at the clock and realize it is covered.  Then I ask, "how do you think people knew what time it was before clocks were invented?" We have a brief discussion on their thoughts. 

I share that before there were clocks people used shadows to tell time. I ask them to think about the term shadow and what they know about shadows. They turn and talk within their groups.  Then I ask groups to share what they discussed.  As I listen to ideas, I post them on the board. Then I ask, "How are shadows created?"  I am looking for students to identify that light and an object are needed to create shadows.

Connecting their Ideas

To help students make this concrete, I hand out a task card ,large white paper, a cup, and a flashlight. They take part in holding the flashlight invarious positions to observe the shadow made by the cup on paper.  I want them to start developing a sense that the position of light on an object affects a shadow's length and size.  

After some time, we discuss the shadows they made and how the amount of light impacted the size of the shadows. 

Explore

45 minutes

Casting Shadows And Measuring Them in the Sun

I tell students we are going outside to begin measuring our own shadows. I explain our task today is to become familiar with the length a shadow makes at certain times of the day. We want to discover how the position of the sun at certain times of the day affects a shadow's size.

I pair each student up. Each pair receives a tracking shadows recording sheet, compass, measuring tape, and chalk. I review the their task and expectations.

Measuring Shadows shadows

Once we are outdoors, I demonstrate how to accurately trace and measure a shadow. I instruct students to find an area to work (I make sure they are spread out enough for working space purposes.) Next, they use the compass to locate north and indicate it with a mark. Since we live in the Northern hemisphere and the sun appears to rise in the east and set in the west; therefore marking the north will give students a clear reading of the sun's apparent movement across the sky.

Then, one student stands facing toward the North while the other student traces the shadow, measures its length, and writes the time on their tracking shadows recording sheet. They swap spots and repeat.

We repeat this process three more times over the week (different times of the day.)(We have a rotating four day schedule, so each day, each class sees me at different times.) Each time,they stand back in the exact spot, trace and measure the shadow, and record the time. They note the position of the sun in the sky, is it on their left, above them, or their right.  I want them to start thinking about how the position of the sun has changed since the first measurement and how it impacts the length of this new measurement.   

Explain

15 minutes

Analyzing Our Data

We engage in a discussion on why shadow lengths change at different times of the day. I ask them questions to create discussion.

  • How did your shadow move?
  • Explain what you think caused the shadow to appear to move.
  • When was the shadow the shortest? longst?  Where was the sun at each of these positions.
  • Thinking about cardinal directions, what direction did the sun appear to rise? set?
  • Knowing the sun does not move, why does it appear to move? 

We talk about how the length of their shadows is relevant to the sun's position in the sky. I explain that their position never changed, meaning each time they casted their shadow, they stood in the same spot, facing the same direction, yet it never changed. It was the sun's position that appeared to change throughout the day.

Evaluate

10 minutes

Evidence Based Analysis

Students use their data to answer questions related to their outdoor shadow activity and graph.  I use these questions to help them summarize their understanding and demonstrate their understanding of how the Earth's rotation causes the sun to appear to move across the sky and accounts for the passing of time.

If times runs out, students finish them for homework. I collect them and use for as a formative assessment.