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Hi Patricia,
This is from my Experiment of the Week e-mail list.
This Week's Experiment - How many coins????
This illusion is so good the you may have trouble believing your own eyes,
much less making someone else believe that it is a simple illusion and not a
more complicated trick.
You will need two similar coins. You can use two pennies, two nickels, etc.
Stack one coin on top of the other and hold them between your finger and
thumb. Now rub your finger and thumb back and forth to cause the coins to slide
back and forth across each other. When you look at it while the coins are in
motion, you will swear that there are three coins.
This illusion is caused by persistence of vision. As you move the top coin
to the end of its path in one direction, it pauses for a second as you reverse
direction. Your eye continues to register the image for a fraction of a
second after the coin is miving in the other direction. Before the image can
fade, the bottom coin has moved into the same position and the image continues.
You see one coin against your finger tip, one coin against your thumb and a
third coin, whose image is made up of the combined afterimages of both top and
bottom coin.
For an interesting variation, use a nickel and a penny. The "third" coin
will seem to be the same as the top coin when viewed from the top and the same
as the bottom coin when viewed from the bottom.
**************
For a sensory illusion, try this one.
This Week's Experiment - #160 Just a Suggestion
This week's experiment comes from our dog, Calley. While visiting some
friends, she got a couple of flea bites. She is very allergic to fleas, and she
has been scratching, in spite of medications. I noticed that the more she
scratched, the more I scratched. No, I did not get fleas too. Instead, the
culprit was suggestion. For this experiment, you will need:
yourself
a clock
This is a very simple experiment, which can show you how much impact your
thoughts have on your body. Find a nice, comfortable place to sit, where you
can see the clock. Now, all you have to do is sit for five minutes without
scratching your nose. That is all. Just don't scratch your nose. Easy,
right? You go for hours without scratching your nose.
How are you doing? Has your nose started to itch yet? No, in spite off
all the rumors about computer bugs in e-mails, I did not send you any
cyber-fleas. The itch is the result of your brain. First, we start with the
suggestion that you not scratch your nose. That implies that your nose will itch.
Sitting there, watching the clock keeps your attention focused on your nose.
Any small sensation becomes the focus of your attention and quickly builds
until you feel that you just have to scratch it.
Some people are more suggestible than others. While some people may be able
to resist scratching for the five minutes, most people will feel the itching
sensation in much less than the time limit. As we have just seen, suggestion
can be a powerful thing. It is used in advertising all the time. Just be
glad that I picked an easy to scratch spot like your nose. Just imagine if I
had told you to think about that spot between your shoulders that is so hard
to reach. Just don't think about it too long.........
**************
If you need more, let me know.
Robert Krampf
Robert Krampf's Science Education Company
www.krampf.com
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