|MadSci Network: Physics|
Dear Deb, You ask a very good question. A shadow is, indeed, a very strange creature. It moves with you, it only appears sometimes, it appears differently at different times, and it does not have any thickness to it. Why is that? Well, shadows are actually caused by a lack of light. Your shadow is caused by your body blocking the light from the sun or from a light bulb. When your body moves, your shadow moves with it because your body blocks the light in the same way, no matter where you stand. Sometimes you can see several shadows. This occurs when several sources of light from different directions are being blocked by your body. Try this experiment. Turn on several lights at different places in a room. Then try to find the shadows that are cast by your body from each light. This tells you something about how shadows form. If you imagine a line from the shadow to your body and continue following that line, it will lead you to the source of the light. Find a shadow of your hand. Now imagine a line from the shadow of your hand, through your hand and continue imagining the line and it will lead you to the light that is causing the shadow. It was a pleasure speaking with you today, Deb. Have fun with your shadow and try out that little experiment. Regards, Todd Jamison Chief Scientist, Observera, Inc.
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