Shadow Stick Clock: A Simple STEM Activity

Can you use the Sun to tell time?

You don't need a clock, a phone, or any special equipment for this simple outdoor STEM activity. With just a stick and a few rocks or pieces of chalk, you can create your own shadow clock and watch how the position of the Sun changes throughout the day.

This is a great activity for slowing down, getting outside, and observing something that is happening around us all the time.

What You'll Need

• A straight stick, about 1–2 feet long

• Several small rocks, pieces of chalk, or other markers

• A sunny outdoor spot.

  • You'll want to choose a place where the stick will stay in the sunlight for several hours.

Build Your Shadow Stick Clock

1. Place your stick

Push the stick upright into the ground. Try to make it as straight and vertical as possible. If the ground is hard, you can place the stick in a container of sand or soil instead.

2. Mark the shadow

Look at the end of the stick's shadow. Place a small rock or piece of chalk at the tip of the shadow. Write down the time next to your mark. For example: 9:00 AM

3. Check it again

Come back about an hour later. The shadow will have moved! Place another marker at the new end of the shadow and record the time. For example: 10:00 AM

4. Keep watching

Continue checking your shadow stick throughout the day. You don't have to check it exactly every hour. Even a few observations can show how dramatically the shadow changes.

Try recording: 9 AM → 10 AM → 11 AM → 12 PM → 1 PM → 2 PM → 3 PM → 4 PM

5. Connect your marks

At the end of the day, look at all of your markers. Connect the points with chalk or simply leave the rocks where they are.

You've created your own outdoor shadow clock!

What's Happening?

The Sun isn't actually moving around Earth each day. Earth is rotating, which makes the Sun appear to move across the sky. As the Sun's position appears to change, the direction of the sunlight hitting your stick changes too. That causes the stick's shadow to change direction and length throughout the day.

You may notice that the shadow is:

• Longer in the morning

• Shorter around the middle of the day

• Longer again later in the afternoon

The exact pattern will depend on where you are, the time of year, and the position of the Sun.

Can Your Shadow Tell Time?

Once you've made several marks, try using your shadow clock to estimate the time. Stand your stick in the same place on another sunny day. Look at where the shadow falls. Which previous mark does it line up with? Can you make a reasonable estimate of the time without looking at a clock?

Take It Further

Want to investigate a little more? Try making observations at different times of the year. Would the shadow pattern be exactly the same?

Or try using two different sticks. Make one stick twice as tall as the other. Do their shadows change in the same way? What stays the same? What changes?

You could record your observations in a simple science journal with the time, shadow length, and a quick sketch.

A Simple Way to Explore Time + Nature

This activity doesn't require a worksheet or a complicated setup. Just put a stick in the ground and pay attention to what happens. Come back later, look again, and notice the change. That's enough to begin exploring Earth's rotation, the Sun's apparent movement, shadows, patterns, and time.

Observe. Wonder. Explore.

And don't forget to look up from your shadow clock every once in a while, and enjoy the sunshine, too.