Hello girls, and welcome to yet another ancient time-keeping technique! We've learned how to use a candle to keep track of minutes--now, let's think a little bigger.
A sundial uses where the sun is in the sky to tell time. At different times of day, the sun is in different places. And when the sun is different spots, shadows go in different directions. We're going to use the direction of the shadows to tell time.
To make a sundial, you will need:
3 pieces of cardboard
A pencil or straight stick
Tape or glue
No adults needed!
We need something for the shadows to fall on. Let's make the face of the clock first.
Put your protractor one inch from the bottom of the cardboard. Every 15 degrees, draw a small line (at 0 degrees, 15 degrees, 30 degrees and so on, just like in the picture below). Label the lines just like in the picture.
Now, we need something to make the shadow. Stick your pencil straight up in the middle of your clock, like this:
Now, here's a tricky part. The Earth is round, so unless your town is right on the equator (an imaginary line that goes around the middle of the Earth), your town isn't really directly facing the sun. It's actually kind of tilted toward the sun. Seriously, it is! So to make our sundial super accurate, and to make it work all day and all seasons, we're going to tilt our sundial, too! You will each tilt your sundial a little bit differently, depending on where you are in the world. Believe it or not, it will make the pencil point straight through the center of the Earth, and the clock parallel to the ground at the North Pole! A tilted sundial is called a gnomon. I think that's pretty fancy!
To find out how much you want to tilt your sundial, first you need to know the latitude (distance from the equator) of your town. You can find it at this web site: http://www.travelmath.com/city/, or in an atlas. Once you've found your latitude, subtract it from 90 to get the angle you want for your sundial. For example, my latitude right now is about 37 degrees. 90-37 = 53. Using your protractors, draw that angle on your cardboard, and cut two wedges from one cardboard that have that angle--for example, one of the corners of my wedges was 53 degrees. Mark which corner of your wedge has the angle you want, or you might get confused!
Now, tape or glue your wedges to the last piece of cardboard on one side and your clock cardboard on another. This can get a little tricky, so check the details. Make sure the pencil is near the bottom, not the top, before you glue, and make sure the two pieces of cardboard form the angle you want, and not the angle of some other corner of the wedge. It should look similar to the one here:
What time did I take this picture?