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Nephoscope
This week we will make a device
called a Nephoscope. It will help us study the movement of clouds. Don't
worry. The name may sound like something complicated, but it is really very
simple.
You will need:
Take the mirror and go outside.
Look up at the clouds for a few minutes. Do they all seem to be at the same
height? Do they seem to be moving? Do you see one shaped like a rabbit? Or
at least one that looks like a rabbit's cotton tail?
The clouds probably seem to be
still, or moving very slowly, although they may be moving very quickly. How
can that be?
Place the mirror, shiny side up,
on a sidewalk or some flat surface on the ground. Sit so that you can see the
reflection of the clouds in the mirror. Keeping your head still, watch the
clouds in the mirror. What do you see? You can probably see the clouds
moving quickly across the mirror.
Why would the clouds seem to be
still in the sky, but seem to be moving in the mirror? To judge movement, we
need something to compare it with. Looking at the clouds in the sky, we can
only compare their movement with other clouds. If they are all moving in the
same direction, they seem to be sitting still. Looking at the reflection in
the mirror, you have the edges of the mirror as a reference point. The sides
are the mirror are not moving, so it is easy to see how fast the clouds are
moving and which way they are going.
Sometimes there will be several
layers of clouds, at different levels. In that case, you may be in for a
surprise. If the different levels are moving in different directions, you may
be tricked into thinking that one layer is moving quickly, while the other is
still. The nephoscope can help you to see the real speed and direction for
each layer of clouds.
You can use your nephoscope to see
the movement of other things too. Try using it at night, to see the movement
of the moon. You may be surprised at how quickly it moves.
Have a wonder filled week.
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