What's In A Shadow?

[Music] la. [Music] Did you ever try to run away from your own shadow? It really can't be done. Your shadow will stick close to you wherever you go. If it's a sunny day, you should make friends with your shadow because it can be a big help in finding directions. Some people think the only way to find directions is with a compass. You probably remember a compass has a magnetized needle that points north. The face under this needle is called a compass rose. Now turn yourself with the compass so that north on the compass rose is under the north pointing needle. You're facing north if you hold it like this. Notice that when you're facing north, east is to your right, west is to your left, and south is behind you. Now, that's important. When you're facing north, east is to your right. West is to your left and south is behind you. But what do shadows have to do with these directions? Well, you might not always have a compass with you, but if you had some sunlight to cast a shadow and a watch or a clock to give you the time of day, you could also find directions. Let's find out how. First, we'll make a shadow diagram. We can record the sun's positions during the day on this sheet. Let's call this a shadow gram. 8:00 in the morning should be early enough to start. We'll mark the sun's shadow each hour. Our clock is a reference for timing the shadow positions and lengths. Now this is taking all day but on film we can compress the time and show it happening faster. [Music] You should experiment with making your own shadow gram. It will be different in different parts of the world and at different seasons of the year. [Music] At 8:00 a.m., our sun's shadow was this line. So, the sun must have been in the opposite direction. The compass needle gives us a north south line on the shadow. Which direction is the sun at 8:00 in the morning? It's east. Now, let's move around to the north side of our shadow so that we're facing south. From here, we can see what the sun appears to do during the day. As we go through the morning hours, the sun seems to move from east to south and climb higher in the sky. [Music] Then at noon time every day, the sun will be observed at its highest point. That's why the shadow line it casts is the shortest one on our shadow gra. And it's lined up north and south. In the afternoon, it's all downhill for the sun. It continues to a point opposite east. [Music] Which direction do you look to see the sun set? Did you say west? Yes. The sun always appears to go down in the general direction of west. Now, why does the sun appear to rise in the east, move across the southern sky and go down in the west? We can answer that if we understand the relationship between the sun and our earth. Let's say this is the sun. It's a big fiery ball, more than 100 times the size of the earth. This is our Earth. The Earth is spinning like a top and turns completely around one time each day. It rotates just like that globe of the world you probably have in your classroom. We'll put you on this globe. Think of the north pole as being at the top and the south pole opposite at the bottom. Then what would your direction of movement be as the earth turns? Eastward. Of course, the earth is always turning toward the east. Once around in 24 hours, one whole day with you coming around into sunlight at dawn. So standing on Earth, in which direction do you look to see the sun appear to rise? The sun will always appear to rise in the general direction of east because that's the direction in which you on the earth are turning. And in which direction do you look to see the sunset? Sunset is always in a westerly direction. Now notice what happens to your shadow as the Earth turns around during the sunlit hours. In the early morning when the sun is in the eastern sky, your shadow would point in the opposite direction. At 12 noon, if you were standing here on this part of the Earth, your shadow would point north. Someone who lives here near the equator might not cast a shadow at all at noon since the sun would be directly overhead. Or for someone who lives south of the equator, the noon shadow would be pointing south. But for everyone, the sun would still appear to rise from the east. During the late afternoon, when the sun is in the western sky, your shadow would point in the opposite direction. [Music] Now, let's see if we've learned anything about finding directions. The zoo is a good place to start because there's usually a map of the zoo grounds. You have to be shown where north is. So, most maps have a north pointing arrow. If you especially wanted to see the children's zoo, how would you find the direction to go from where you are? You're standing at this point on the map. The Children's Zoo is here. Now, how can you tell in what direction you must go to find it? [Music] >> Compare the direction you want to go to the north pointing arrow on the map. The direction you want to go happens to be south. The time is 9:00 in the morning and the sun is shining. Your shadow tells you the sun is in that direction. You know, at 9 in the morning, the sun is still in an easterly direction. So, east is about there. And if east is on your right hand, which way is south? Yes, it's behind you. The direction in which you want to go to find the children's zoo. [Music] If you were at the zoo at 4:00 in the afternoon on a sunny day, could you find your directions? You could find west because that's where the sun would be late in the day. >> And once you know where west is, then you can find any of the other directions, can't you? Yes. Knowing any one direction, you can find each of the others. Remember, if the shadow tells you that east is on your right or west is on your left, then you're facing north and south is behind you. [Music] Why don't you look at the time and find a shadow right now? Then see if you can figure out the direction of north. [Music] Don't try to leave your shadow behind, though. You'll need it the next time you want to find directions. [Music]