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Pretend Telescope
The other interesting science news this week is Mars.
Despite what you may have read in e-mails, Mars will not appear as large as the
moon. Still, it is quite bright, and it shows its red color well. With a
telescope, it is even better. I know that most people do not have a telescope
laying around, but your local science museum or astronomy club is probably
having telescope viewings.
Since we don't have a telescope laying around, we will
have to fall back on a childhood pretend telescope that interestingly does help
you see a little better. It won't help you see Mars, but you will learn a
little science.
To try this, you will need:
Most kids at one time or another have picked up the
cardboard tube from a roll of paper towels and pretended that it was a
telescope. As we will see, there is more than imagination at work here.
Place the book on a chair or table, propped up so that you can read the pages.
Back away slowly until the words are difficult to read. You want to be just at
the point were you can almost read the type. Hold the tube to your eye, as if
it were a telescope. Looking through it, try to read the print again. You
should be able to read it now.
Now wait a minute! How can a simple tube help you see
better? Lets think about it. What is the tube doing? It is blocking all
the light coming from the sides, letting you focus just on the printing. But
something else is happening. Your eye reacts to the reduced light. If you
look at your eye in the mirror, the black spot in the middle is called the
pupil. It is a hole that lets light get to the inside of your eye. Around
the pupil is the colored part of the eye, called the iris. In low light, the
iris contracts, so the opening of the pupil gets larger, letting in more
light. In bright light, the iris expands, making the pupil smaller to
protect your eye from too much light.
Since the tube blocks most of the light, your pupil
opens wider. This sharpens the image slightly, to let you see a little
better. It will not help you see Mars. Since it is already dark outside, the
tube does not block much light, so it does not make much difference.
You can test this experiment by doing it again. This
time, once you can see the print, quickly remove the tube. You will find that
you can still see the print for a second or two. Your pupil is still open
wider, so you can still see just a tiny bit better until it returns to normal.
Have a wonder filled week.
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