A sundial is a device that uses the position of the sun to determine time. The upright wand, called the gnomon, is positioned to cast a shadow on the pre-marked sundial. As the sun moves across the sky, its shadow will also move. This concept can be easily demonstrated in your backyard with a very simple sundial made with a stick and a handful of pebbles. There are also many other easy projects that children can do to learn the concepts. For something a little more advanced, you can make a permanent sundial in your garden or backyard. With a little measurement and carpentry work, this watch will tell you the time with great accuracy.
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Method 1 of 3: Using Sticks and Stones
Step 1. Gather equipment
This very basic sundial is a great way to explain this concept with a little planning. All you need to make them are some simple items found in the backyard. These tools are a straight stick (about half a meter long), a few grains of pebbles, and a watch or cell phone to tell the time.
Step 2. Find a sunny area to attach the stick
Look for a spot that gets full sun exposure throughout the day. Dip one end of the stick into the grass or soil. If you live in the Northern Hemisphere, tilt the stick slightly towards the North. If you live in the Southern Hemisphere, tilt the stick slightly towards the South.
- If you can't find areas of soft grass, improvise.
- Fill a small bucket with sand or gravel and plant a stick right in the middle.
Step 3. Start at 7:00 am
If you want to finish making your sundial in one day, start in the morning after the sun is fully up. Observe the sticks at 7:00 am. When the sun shines on it, the stick casts a shadow. Use one of the pebbles to mark where the shadow falls on the ground.
Step 4. Re-examine the stick every hour
Set an alarm or keep an eye on your watch so you can update your sundial every hour. Observe again at 8:00 am and use another pebble to mark where the stick's shadow fell on the ground. Do the same thing at 9:00 am, 10:00 am, and so on.
- If you want a high degree of accuracy, use chalk to mark each pebble at the exact time you place it on the ground.
- The shadow will move clockwise.
Step 5. Continue this process until evening
Come back every hour and mark with gravel on the ground. Do this until there is no more sunlight during the day. Your sundial will finish at the end of the day. As long as the sun is shining, you can use this simple device to find out what time it is.
Method 2 of 3: Using Paper Plates and Straws
Step 1. Gather equipment
This easy sundial is a great project for kids on a hot summer day. The tools needed are very simple - you probably already have all of them at home. These items are crayons / markers, paper plates, sharp pencils, push pins, rulers, and straight plastic straws.
Start preparing the paper plates around 11:30 p.m. on a sunny, cloudless day
Step 2. Write the number 12 on the edge of the plate
Use crayons or markers for this. Take a sharp pencil and stick it in the center of the paper plate. Remove the pencil so you get a hole in the middle.
Step 3. Use a ruler to draw straight lines
Draw from the number 12 to the hole you made in the center of the plate. This number represents 12 noon.
Step 4. Use a compass to determine the nearest celestial pole
The straw, or your gnomon, should point to the nearest celestial pole, which is parallel to the earth's axis. It is the North Pole for those who live in the northern hemisphere. If you live in the Southern Hemisphere, it is the South Pole.
Step 5. Take the plate outside just before noon
Place it in the ground in an area that will get full sun exposure throughout the day. Stick the straw in the hole in the center of the plate.
Step 6. Press the straw lightly
Do this so that the straw is angled towards the nearest celestial pole.
Step 7. Turn the plate exactly during the day
Rotate it so that the straw shadow is parallel to the line you drew. Since you're only measuring daylight hours, the plate will look like a clock showing only 12 hours.
Step 8. Place the plate on the ground
Stick a few push pins through the plate to keep them from sliding.
Step 9. Look at the plate again an hour later
At 1 pm, look at the plate again and check the position of the shadow of the straw. Write the number 1 on the edge of the plate where the shadow falls.
Step 10. Set an alarm and come back out every hour
Continue to mark the position of the shadow falling on the edge of the plate. You will observe that the shadow moves clockwise.
Step 11. Discuss with your child about the shadow
Ask why they think the shadow is moving. Explain what happens when the shadow moves around the sundial.
Step 12. Repeat this process until evening
Keep marking the plates every hour until your daylight ends. At this point, the sundial will be complete.
Step 13. Check the plate the next day
Ask your child to look back at the plate the next sunny day and tell you the time based on the position of the shadows. This simple device can be used to determine the time of day on a sunny day.
Method 3 of 3: Making an Advanced Sundial
Step 1. Cut a circle 50 cm in diameter from 2 cm thick plywood
This circle will be the face of the sundial. Coat both sides of the wooden circle with primer. As the primer dries, think about what you want the sundial to look like. You need to choose a number style, such as Roman numerals, standard numerals, and so on.
- Choose the color you want to use and, if you like, an image or illustration to attach to the face of the watch.
- Sketch several different designs until you choose a final design.
Step 2. Draw your final design on a large piece of paper circle
You will use this design as a stencil to transfer the design onto the wooden circle. So, draw to scale. Now you need to enter the numbers into the design, which requires a bit of precise measurement. Use a straight line and a protractor to do this.
- Start with the number 12 at the very top, like the face of a clock.
- Measure the location of the center of the circle, then use a ruler to draw a straight line from number 12 to the center of the circle.
Step 3. Use a protractor to measure exactly 15 degrees to the right
Mark the number 1 there. Use a ruler to draw another clock line. Continue to mark the numbers exactly 15 degrees apart. Move clockwise and use the protractor to continue marking the numbers. Continue until you reach 12. This will be directly opposite the first 12. These two numbers represent day and night.
- Then start with 1 again until you get back to the first 12 at the very top. These numbers are now accurately marked on paper.
- The full 24 hours are represented for the greatest degree of accuracy. As the seasons change, so does the position of the Earth. In summer, the days are longer. In winter, the days are shorter.
- There are days in summer when daylight lasts more than 12 hours.
Step 4. Paint your design on the wooden circle
Use your paper as a stencil so that the numbers and hour lines match what you've measured exactly. Use a paint marker to place the numbers on the wood as this will involve fine detail work. Paint markers are better than permanent markers because they are more resistant to the elements.
Step 5. Create a gnomon
The gnomon is the part of the sundial that will cast a shadow. Use a threaded pipe, and you will need to measure it approximately 5 or 7.5 cm long. The diameter is 1.25 cm. Make sure the diameter of the gnomon is slightly wider than the pipe itself. Make the ends conical.
- The length of the pipe and the tip of the gnomon should not exceed 7.5 cm.
- Paint the gnomon any color you like. This will prevent it from rusting.
Step 6. Prepare the sundial mounting posts
The face of the sundial, namely the wooden circle, will be installed on this post. You will need a 4x4x8 wooden plank bollard that has been installed outdoors. These bollards should be perfectly straight and not have large cracks in them. To install properly, the top of the bollard must be cut at a right angle.
- To get this angle, subtract 90 degrees from your current latitude.
- For example, if you are at latitude 40 N, draw a 50 degree angle on a 4x4 plank of wood.
Step 7. Cut the corners on the posts
Draw a line at the right corner using a carpenter's ruler. Draw this line 15 cm from the top of the post. This line is the lower side of the corner. Use a protractor to measure it, then cut the angle with a saw.
- Then measure the center of the sundial face and drill a hole there.
- Test the mounting of the post to the sundial face with 2 mm screws, just to make sure everything is securely in place.
Step 8. Dig holes for the posts
Find a sunny spot for your sundial and dig a hole to attach the post to. Make sure you don't interfere with underground cables or lines. Insert the bollard into the hole. Test it to make sure it is 1.5 meters off the ground when standing upright. Use a compass to make sure the angle you cut on the post is facing north. Use a level level to ensure that it is in an upright position.
- Fix the bollard permanently by pouring cement on the bottom.
- Allow a few days to pass before attaching the sundial face to allow the cement to dry completely.
Step 9. Attach the sundial face to the post
Use 2 mm diameter screws 5 cm long to attach the face. Tighten the screws enough so that they hold the face in place, but you can still easily turn the face over. Place the flange just above the face of the sundial.
- You should be able to see the screw in the center hole of the flange.
- Use your right hand to attach the gnomon pipe to the flange, which you should hold in your left hand.
Step 10. Rotate the face of the sundial so that the 6 am and 6 pm lines are horizontal
Then adjust the gnomon so that the same line looks like it goes straight to the center. Make sure the line at 12 noon also looks like it's right through the gnomon.
Step 11. Set the time and install gnomon
You must set the time during Daylight Savings Time for an accurate reading. Hold the flange with your left hand. Use your right hand to rotate the sundial face. Check the current time. Keep turning the face until the gnomon's shadow shows the same time as the sundial. Use a pencil to mark where the four flange screws are and then remove the flange.
- Now tighten the screws. Do not move the sundial face while you do this.
- Drill holes for the four screws and then tighten the flange on the sundial.
- Finally, install gnomon in its place.
