Sundials- Telling Time!

Purpose:

The purpose of this lesson is to explore the use of the sun and its ability to help us tell time with a man-made sun dial and shadow activity. This lesson also promotes the STEM (Science, Technology, Engineering, and Mathematics) by integrating the Engineering Design Process in a cross-curricular lesson.

Lesson Goal or Objectives:

Students will build sundials and observe shadows as the Sun's position changes over time.

Students will measure shadows and note the position of the Sun using a protractor and meter stick.

Students will identify patterns of change in the shadows. 

Students will share data with peers and discuss how sundials serve as clocks.

This lesson will address the misconception that sundials are cabalistic where people think they are related to a mystical interpretation with a hidden, mysterious meaning.

Lesson STEM Challenge Question:

How does the design of a sundial affect a human’s ability to tell the correct time of day?

Target Group:

This activity is appropriate for students in fourth grade. The lesson could be modified for students in fifth grade or beyond by creating a harder, more elaborate sundial where measurements are more precise.

Estimated Time:

Teacher Prep: One hour to gather materials, create handouts.

Student: Approximately one full day to gather data for shadows at various times and complete all activities.

Background Information:

Historical Perspective:

Sundials have been used since ancient times to mark the time. They were even used to check the accuracy of early mechanical clocks. Sundials work because as the Earth rotates around the sun, the sun’s place in the sky changes.

There are different types of sundials. Some sundials use a shadow or the edge of a shadow while others use a line or spot of light to indicate the time.

The shadow-casting object, known as a gnomon, may be a thin rod, or other object with a sharp tip or a straight edge. Sundials employ many types of gnomon. The gnomon may be fixed or moved according to the season. It may be oriented vertically, horizontally, aligned with the Earth's axis, or oriented in an altogether different direction determined by mathematics.

With sundials using light to indicate time, a line of light may be formed by allowing the sun's rays through a thin slit or focusing them through a cylindrical lens. A spot of light may be formed by allowing the sun's rays to pass through a small hole or by reflecting them from a small circular mirror.

Sundials also may use many types of surfaces to receive the light or shadow. Planes are the most common surface, but partial spheres, cylinders, cones and other shapes have been used for greater accuracy or beauty.

Sundials differ in their portability and their need for orientation. The installation of many dials requires knowing the local latitude, the precise vertical direction (e.g., by a level or plumb-bob), and the direction to true North. Portable dials are self-aligning; for example, it may have two dials that operate on different principles, such as a horizontal and analemmatic dial, mounted together on one plate. In these designs, their times agree only when the plate is aligned properly.

Sundials indicate the local solar time, unless corrected for some other time. To obtain the official clock time, three types of corrections need to be made.

First, the orbit of the Earth is not perfectly circular and its rotational axis not perfectly perpendicular to its orbit. The sundial's indicated solar time thus varies from clock time by small amounts that change throughout the year. This correction — which may be as great as 15 minutes — is described by the equation of time. A sophisticated sundial, with a curved style or hour lines, may incorporate this correction. Often instead, simpler sundials are used, with a small plaque that gives the offsets at various times of the year. Second, the solar time must be corrected for the longitude of the sundial relative to the longitude of the official time zone. For example, a sundial located west of Greenwich, England but within the same time-zone, shows an earlier time than the official time. It will show "noon" after the official noon has passed, since the sun passes overhead later. This correction is often made by rotating the hour-lines by an angle equal to the difference in longitudes. Last, to adjust for daylight saving time, the sundial must shift the time away from solar time by some amount, usually an hour. This correction may be made in the adjustment plaque, or by numbering the hour-lines with two sets of numbers.

Sun Clocks. What is a sundial? Retrieved March 13th, 2014, from

http://www.fi.edu/time/Journey/Sundials/aboutsd.htm

Students work in small groups to investigate teacher-selected electronic sites focused on how a sundial works and how they are built. Students identify information that is important from the electronic sources. Using their own words, the groups will document the most important information contained in the reading by writing down facts in their notebooks.

Vocabulary and Concepts:

Circumference- the length of the closed curve of a circle

Diameter- the length of a straight line passing through the center of a circle andconnecting two points on the circumference

Gnomon- a vertical pointer that will indicate noon correctly when its shadowpoints north

North Latitude- the angle between the North Star and the base of the sundial

North Pole- the north end of the axis of rotation of the earth or any astronomicalObject

Radius- the length of a line segment between the center and circumference of acircle or sphere

Shadow- a dark shape cast on a surface caused by an object blocking light

Sun– the star at the center of our solar system around which the earth and eightother planets rotate

Angle: The figure formed from two lines extending from the same point. Also, the measure of the degree to which the two lines “open” or fail to be parallel.

Alignment: Three objects are in alignment if one straight line can be drawn passing through allthree.

Similar: Identical in shape but different in size, orientation, or position.

This activity will use elementary of the elementary Engineering Design Process developed by Engineering is Elementary http://www.mos.org/ele/engineering_design.php. “There are many variations of the engineering design model. The one provided by EiE is intended for younger learners and has fewer steps and appropriate terminology that children can understand. It is important to remember that like scientists, practicing engineers do not adhere to a rigid process. There are many variations and the process is cyclical. Like the inquiry model, this process can begin at any step and move back and forth between steps. Like scientists, engineers share their ideas with other teams.

“Moving through the process might involve asking the following questions or making the following decisions:Ask: What is the problem? What have others done? What are the constraints?

Imagine: What are some solutions? Brainstorm ideas Choose the best one

Plan: Draw a diagram Make lists of materials you will need

Create: Follow your plan and create it Test it out!

Improve: Talk about what works, what doesn’t, and what could work better. Modify your design to make it better Test it outAfter you improve your design once, you may want to begin the Engineering Design Process all over again to refine your technology. Or you may want to focus on one step. The Engineering Design Process can be used again and again!”

Engineering is Elementary. Retrieved October 2, 2012. http://www.mos.org/ele/engineering_design.php.

Discipline-based Michigan Science Content Expectations:

Science Content Expectation:

E.ST.04.11- Identify the sun and moon as common objects in the sky.

Technology:

3-5.RI. Research and Fluency- Use digital tools to find, organize, analyze, synthesize, and evaluate information.

3-5.CT. Critical Thinking, Problem Solving, and Decision Making- Use digital resources to access information that can assist in making informed decisions about everyday matters (e.g., which movie to see, which product to purchase).

Engineering Standards:

Engineering Design 1D2: Designing, testing, and building a system, component, or process to meet desired needs within realistic constraints.

Common Core: Mathematics: Fourth Grade:

Solve problems involving measurement and conversion of measurements.CCSS.Math.Content.4.MD.A.1- Know relative sizes of measurement units within one system of units including km, m, cm; kg, g; lb, oz.; l, ml; hr, min, sec. Within a single system of measurement, express measurements in a larger unit in terms of a smaller unit.Geometric measurement: understand concepts of angle and measure angles.

CCSS.Math.Content.4.MD.C.6- Measure angles in whole-number degrees using a protractor. Sketch angles of specified measure.

Materials Needed:

Paper plates (1 per student during explain)Plastic straw (1 per student during explain)Crayons, colored pencils, or markers (1 box per group during explain)A sharpened pencil (per student for all activities)Plasticine (1 during explain)Tape (1 roll during explain)Meter Stick (2 per group during explore)Compass (1 per group during explore)Chalk (few pieces per group during explore)Protractors (2 per group during explore)“What Time Is It” Worksheets (1 per student during pre-assessment and engage)“Sundial Data Sheets” (1 per student during explore to record info)“Checklist” (1 per student for evaluate)“Rubric” (1 per student for evaluate)

References:

Crayola. Human sundial. Retrieved March 13th, 2014, from

http://www.crayola.com/lesson-plans/human-sundial-lesson-plan

Engineering is Elementary. Retrieved October 2, 2012. http://www.mos.org/ele/engineering_design.php.

Eye on the Sky. Sundials: observing and using shadows. Retrieved March 13th, 2014, from

http://www.eyeonthesky.org/lessonplans/14sun_sundials.html

National Wildlife Federation. Paper plate sundial. Retrieved March 13th, 2014, from http://www.sciencetech.technomuses.ca/english/whatson/pdf/astronomy-resources/paper-plate-sundial.pdf

Partnerships Implementing Engineering Education. Sundial wristwatch. Retrieved March 13th, 2014, from http://www.wpi.edu/Images/CMS/PIEE/5b1.pdf

Solar Matters. Making a sundial. Retrieved March 13th, 2014, from http://www.fsec.ucf.edu/en/education/k-12/curricula/sm2/documents/SM2_making-a-sundial.pdf

Sun Clocks. What is a sundial? Retrieved March 13th, 2014, from

http://www.fi.edu/time/Journey/Sundials/aboutsd.htm

Safety Considerations:

Students should use tools with care. Do not use to harm others and be aware of your surroundings. If it is very warm outside, use sun protection and wear appropriate clothing.

STEM LESSONEngage and Pre-assessment:

Show students pictures of different types of sundials. Introduce the topic and talk about how the sun can serve various purposes.

Distribute “What Time Is It” worksheets that have students read and complete the questions. (Attached at end of lesson)

Go over the worksheet with students and ask for volunteers to read their responses out loud. Lead into a discussion while getting the students’ opinions.

Procedures:

Explore:

Ask students, “Do you think you would be able to tell the time of day, using your shadow?"

Explain to them that we are going to be doing a fun activity outside in groups. Groups will have 4 students each and they will take turns measuring each student’s shadow. Tell students we are going to be creating a human sundial and we will measure out the shadow angles using protractors, record the time of day, how long the shadow is in terms of meters, and where the location of the sun is in the sky at that time (North, South, East, and West). Students will go outside 4 times throughout the day, twice in the morning, and twice in the afternoon. They will record this information on their “Sundial Data Sheets.”

*If it is a cloudy or rainy day outside, the activity will need to be postponed. If there is no flat surface where chalk can be used, activity will need a new location.

Instructions:

Locate a large, safe outdoor area to draw your human sundial, which will give you an idea of how a sundial works. Make sure it is in full sun.

Using Crayola Giant Sidewalk Chalk, draw a large circle. Make sure the top of the circle where you will start with the number 12 is pointing North. The teacher will demonstrate with a compass how to find the North direction. Each group will receive one compass to model. Make evenly spaced marks around the outside edge for each hour of the day. Figure out where the center of the circle is located and mark that, too.

Stand on the center mark in the morning around 9 am when the sun is out. Ask a classmate in your group of 4 to trace where your shadow falls on the sundial. Inside the traced shadow, write the time of day. Then go on to record the angle of the shadow using a

protractor, the length using a meter stick, and where the sun is in the sky by using your background knowledge (Hint: Never Eat Soggy Waffles). Keep recording your results throughout the day to see how the shadow moves around the sundial. Use different colors each time you experiment. Additional times of the day will be at 11 am, 1 pm, and 3 pm.

After each tracing, fill out all the correct information on your data sheet.

Student Demonstration and Reflection:

At the end of the activity ask students, “How accurate do you think your sundial is? Why?”

Explain:

Science Discussion:

Teaching Points: We are going to be building our own sundials. Read info from background information up above and go over some of the vocabulary terms to make sure they understand.

Have students get back into the groups they were in for the explore activity. In groups, they will make one sundial and decorate it.

Building Sundials

Students will all receive a paper plate, something to color with (crayons, colored pencils, or markers), a straw, plasticine, and a pencil. They will need to determine how to create a sundial using these materials. No further instruction will be given and they will need to go through the design process to create, test, and improve their model.

Put the Design Process (that is below) somewhere where it is displayed at the front of the room for the class to see. Students will look and check to make sure they are working through their sundial design correctly.

The Design Process:

Ask:

What is the problem? What have others done? What are the constraints?

Imagine:

What are some solutions? Brainstorm ideas

Choose the best one

Plan:

Draw a diagram Make lists of materials you will need

Create:

Follow your plan and create it Test it out!

Improve:

Talk about what works, what doesn’t, and what could work better. Modify your design to make it better Test it out

After students improve their design once, they may want to begin the Engineering Design Process all over again to refine their technology. Or they may want to focus on one step.

Elaborate:

Scenario: We are back in ancient times and have no way of knowing what time it is. Using our newly built sundials, we will go outside to determine the time.

How to Use the Sundial

Sundials work best when placed in full sunshine. Choose a flat surface for your sundialon a sunny day. Ensure that the number 12 is pointing North. You can do this with a compass, or by going outside at noon and carefully turning the plate until the shadow of the straw falls in line with the number 12. Your sundial is now in the proper position. You should now be able to tell the time of day by looking at the shadow cast on the surface of the dial by the straw.

Real-World Connections:

Have students go online and look up places where they can actually purchase sundials. Look at images of different kinds and write down the store and price of each one. Go home and show their parents what they found and tell them what they learned today.

Post Assessment:

Students use their data work sheets during this discussion.

Discuss with the class:

1. What did you observe? What did the shadows do? 2. When was the shadow the longest? Where was the Sun? 3. When was the shadow the shortest? Where was the Sun? 4. Why do you think the shadows change length? How can you explain what you are

observing?5. What was the difference in angles throughout the day?6. How could you use a shadow to tell the time of day?

After some responses, have students write down one thing they learned from the lesson in their notebook. The teacher will go around and check to see what each student has wrote.

Evaluate:

The teacher will monitor student engagement in the whole process throughout the activities with a checklist. Students will be graded individually in how they cooperated with the whole group and worked as a team player. (Checklist at end of lesson).

The teacher will also evaluate students on the design process individually. (Rubric at end of lesson).

What Time Is It?Long before the invention of the watch or the clock, people made up ways to mark the passage of time. One way was for a person to watch the length of his shadow. At dawn, his shadow was very long. The closer it got to noon, the shorter the shadow became. Then during the afternoon, this shadow began to grow longer and longer. At sunset it was exactly the same length as at sunrise. The invention of the sundial was based on the same idea. A sundial has a metal post pointed straight up. As the sun moves, the shadow moves. A sundial has special markings to tell the minutes and hours of the day. However sundials cannot help us keep track of time at night or on dark, cloudy days.

Modern day clocks and watches tell us the time - night and day, rain or shine.There are two kinds of watches and clocks: analog and digital. Analog clocks show the hours and minutes of the day on the perimeter (or around the edge) of a circle. Two hands rotate around a point in the center and we tell time according to their positions on the circle.

Analog Clock Digital Clock

Digital clocks are easier to read. Digital clocks show the hour and minutes in digital form; the hour and the minutes appear as numbers, separated by a colon(:).Years ago, all analog clocks and watches needed to be wound regularly. Today most analog and all digital timepieces are battery-operated. Many people believe that analog clocks and watches are old-fashioned and will soon become a thing of the past.

Name:

Answer the following questions:

1. Before the invention of modern day clocks and watches, how did people tell time?

2. How do you think sundials work? Why are sundials useless at night?

3. What kinds of watches and clocks are available today? Which is easier to read? Why?

4. In your opinion, do you think children still need to learn to read both kinds of clocks?

Sundial Data SheetName: Date:

Time of Day(am/pm)

Length of Shadow

(m)

Angle of Shadow

(degrees)

Where is the sun in the sky?

(N, S, E, W)

1.

2.

3.

4.

ChecklistName:

Skills None of the Time

-

Some or Most of the Time

All of the Time

+

Points

(0, 1, 2)

Helping

The teacher observed the student offering assistance to others on the team.

Listening

The teacher observed student working from other’s ideas.

Participating

The teacher observed each student contributing to the project

Persuading

The teacher observed the student(s) exchanging, defending, and rethinking ideas.

Questioning:

The teacher observed the student(s) interacting, discussing, and posing question questions to all group

members of the team.

Respecting

The teacher observed the student encouraging and supporting the ideas and efforts of others.

Sharing

The teacher observed the student offering ideas and reporting findings to others on the team.

Rubric- Design ProcessName:

Engineering Principles

0-2 points 6-7 points 8-9 points 10 points

ASK No evidence of questions

Evidence of concrete, procedural questions

Questions are directly linked to engineering design process

Questions are directly linked to engineering design process and the client’s needs

IMAGINE No evidence of schematic designs

Limited and vague sketches

Sketches reflect understanding of the engineering design process

Sketches reflect understanding of the engineering design process and attention the client’s needs

PLAN No evidence of a plan.

Limited and/or lacks attention to details.

Reveals an understanding of the feasibility of the engineering design process.

Reveals an understanding of the feasibility of the engineering design process and the necessity of meeting the client’s needs.

CREATE No evidence of a working model.

Has a working model; het limited in design and operation.

Model illustrates a moderate level of sophistication in design and operation.

Model illustrates a high level of sophistication in design and operation.

IMPROVE No evidence of a re-design.

Minor changes performed on re-

Changes made to model were

Changes made to model were

design. informed by structural limitations.

informed by structural limitations and addressed client’s needs.

Earned Points= _______/50