Who set the first clock?
Who set the first clock?
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DISCUSS:

How do you think the very first clock got set, when there was no other clock to look at?

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DISCUSS:

Long ago, people did not have the concept of hours or minutes. Someone had to come up with these ways to divide a day into parts.

How would this week have gone wrong for you if you could only measure time in days?

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DISCUSS:

Try counting like an Egyptian! Use your thumb to count all of the finger segments on that same hand.

How many finger segments do you have on one hand?

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DISCUSS:

So why do you think there are 24 hours in a day?

See what we thought...

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DISCUSS:

What happens to the shadows as time passes?

How could you use shadows to measure the Sun's position?

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# Why are the shadows moving so fast?

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###### Which direction are you facing when you sit in this chair? North, South, East, or West?

Here's how we figured it out:

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###### How is the movement of the clock’s hands like the movement of the shadow?

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Here’s a game to play outside on a sunny day. Find a place where the shadow of a building or wall makes a straight line. Mark that line with chalk.

Ask students to predict where the shadow will be in 15 minutes. Mark their guesses with other colors of chalk.

In 15 minutes, mark where the shadow ended up. How close were the guesses? Try again to see if you can do better.

This game is best when the sun is low in the sky. Don’t play at noon, when the sun is high in the sky.

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# Image & Video Credits

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Other
clock by TBIT / cropped, adjusted color
 Exploration 20 min Hands-On Activity 25 min
Print Prep
Activity Prep

In this Mystery, students will learn why our ancestors divided the day into hours and how clocks measure the Sun’s apparent movement. In the activity, Make a Shadow Clock, students make their own sundials. First, students use flashlights indoors to understand how the position of the light affects the time shown on the clock. Then, students take their shadow clocks outside to see how the position of the Sun can tell them the time of day.

Number of students:
 Shadow Clock Template worksheet Use Google to find your latitude, then print your clock template. 1 per pair Used to make Cardinal Direction signs for the classroom. Recycled is fine. Details 4 sheets per class Tape works too. Details 1 glue stick per student 1 ruler per student 1 pair per student 1 plate per student 1 toothpick per student 1 stick per class 1 flashlight per pair You can also use clay or Playdough. Details 1 strips per student

We suggest students work in pairs. Homeschool students can work on their own.

Each Shadow Clock printout has two templates on it. Once you print these out, cut each in half so that each student will have one.

# Label Classroom Walls with Cardinal Directions — North, South, East, West

When students are experimenting in the classroom, they need to orient their Shadow Clocks so the arrow points North.

Make four signs — North, South, East, and West.

Here’s one easy way to figure out where each sign goes:

2. Zoom in on your school and look at surrounding streets and landmarks.
3. North is always up on Google Maps. Find a landmark that’s to the north of your school.
4. Put North on the wall that’s closest to that landmark.
5. Face North. Put West on the wall to your left, East on the wall to your right, and South on the wall behind you.

# Find North Outside and Draw Arrows with Chalk

The main activity is completed indoors, but we recommend that students test their Shadow Clocks outside on a sunny day. They’ll need to orient their Shadow Clock with the arrow pointing North. We recommend that you sketch several compass roses on the ground in chalk to serve as workstations.

The easiest way to find exact North when you are outside is to use a Shadow Clock. Turn the shadow clock to match the current time. Now the compass rose you made on the Shadow Clock will be properly oriented.

A magnetic compass, whether an old-fashioned kind or those available on many smartphones (such as iPhone’s compass app), actually points toward the Earth’s magnetic North Pole, which is slightly off from the geographic North Pole, depending on where you are. It may cause some error, depending on your location.

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