Fun Science Idea

An astrolabe is an instrument used by early mariners to find latitude. Latitude is how far in degrees a point on the earth is from the equator. 0 degrees latititude is on the equator. 90 degrees is at the North Pole. You can make an astrolabe that will measure the latitude of where ever you happen to live. About all you need are a piece of cardboard, two paperclips, glue and a protractor. You will need to be able to find the North Star.

Straighten the wire of a paperclip. Bend the middle of the wire around a nail to make a loop such as that of a safety pin. The wire ends should be parallel or somewhat closer together. Make a second such shape from another paperclip. Get a piece of stiff cardboard something like 12 inches by 12 inches.
Place the paperclip pieces on one edge of the cardboard, one near each end of that edge. If the clips are bent just so, the two wire ends will grip the cardboard to keep the wire in place temporarily. Make sure the loop of both pieces are the same distance above the edge of the cardboard. The loops should be turned so you can look through them as sights of a gun. When they are lined up correctly, glue them in place.

Place a pencil mark at about the center of the edge that has the paperclips attached. Just guess where the middle of the edge is. Use the corner of something square such as a piece of writing paper, as a guide to draw a line that forms a 90 degree angle with the edge of the cardboard. Start the line at the mark. Glue the end of a two foot long string to the edge of the cardboard at the mark.

When the glue has dried, attach a small weight such as a large paperclip to the end of the string. To use the astrolabe, sight the North Star through the two wire loops. With the thumb and index finger, clamp the string againt the cardboard where it crosses the lower edge of the cardboard. Place a pencil mark along the string where you are holding it. Use a straight edge to draw a line between the mark at the glued end of the string and the mark you just drew. Measure the angle between that line and the 90 degree line. That number of degrees that you measure is also the latitude in degrees of your location.

You are at about 45 degrees latitude and using the astrolabe. The sights of the astrolabe are practically parallel to the axis of rotation of the earth. This will always be the case anywhere on the northern hemisphere because the North Star is so far away.

You are on the equator and the astolabe tells you that the latitude is 0 degrees.

You are at the North Pole and 90 degrees north latitude.

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