|
Robert Krampf's Experiment of the Week |
|
|
|
This Week's Experiment - #186 Measuring Raindrops |
|
|
|
Last week's experiment is going to be a hard act to follow. It got more |
|
comments than I have gotten in quite a while. For instance, Craig Combs |
|
pointed out that it explains why people squint when they are looking at |
|
things without their glasses. When you squint, your eyelid and eyelashes |
|
form "pinholes" which let you see without your glasses. Many people also |
|
wrote back that it was nice to have an experiment that had a useful |
|
application in daily life. |
|
|
|
This week's experiment may not be nearly as useful as last week's, but it is |
|
interesting and may be surprising to many people. Since Hurricane Gordon is |
|
headed our way, I thought I would do an experiment on rain. I set out for an |
|
easy way to demonstrate the shape of a raindrop (which is not the tear drop |
|
shape that most people think of). While I have not found a simple way to |
|
demonstrate that yet, I did find another fun, rain related experiment. It |
|
has to do with measuring the size of raindrops and showing that in most |
|
storms there are drops of many different sizes. You will need: |
|
|
|
a shallow pan or bowl |
|
flour |
|
a rainy day |
|
a sieve, colander or piece of window screen. |
|
|
|
Put about an inch of flour into the pan. I found that it helps if you sift |
|
the flour into the pan, to get rid of any lumps, but it is not necessary. |
|
Now, you want to collect some raindrops in the pan. You want to get enough |
|
raindrops for a good sample, but not enough to turn your experiment into |
|
pancake batter, although pancakes might be a nice snack to eat while you are |
|
experimenting. How long you hold the pan in the rain will depend on how hard |
|
it is raining. Right now, it is raining fairly hard, so one quick out and |
|
back of the pan was enough to get quite a few raindrops. |
|
|
|
Once you have your raindrops, the first thing to do is to look at holes they |
|
made in the flour. I quickly noticed that not all the holes were the same |
|
size. In fact, there was a wide variety of sizes. That is exactly what the |
|
originator of this experiment was trying to show. His name was Wilson A. |
|
Bentley. |
|
|
|
Wilson Bentley was a farmer in Jerico, Vermont during the late 1800s and |
|
early 1900s. He was also VERY interested in snowflakes and became famous for |
|
his work in photographing and studying them. During the summer, when he |
|
could not study snow, he studied rain instead. He wanted to photograph |
|
raindrops, and found that he could preserve their impressions in wheat flour. |
|
He also discovered that at the bottom of each "crater," there was a small |
|
pellet of dough. Careful experimentation showed him that these pellets were |
|
the same size as the raindrop that made the impression. He collected sets |
|
pellets from many different rainstorms and found that there was almost always |
|
a wide variety of sizes. In 1904, he published his results in the October |
|
issue of Monthly Weather Review. |
|
|
|
You can see the same thing by letting your pan of flour sit over night to dry |
|
and then carefully putting it through a sieve. This will let you collect the |
|
pellets from the sample and see the range of sizes from your rain sample. |
|
Place the pellets onto a plate and sort them according to size. |
|
|
|
Bentley found that there were almost always many more small drops than large |
|
ones. He also found that the largest drops fell from cumulonimbus clouds and |
|
that there were larger drops when there was lightning directly overhead. If |
|
you want to read more about Bentley and his experiments, go to: |
|
http://www.islandnet.com/~see/weather/history/rdbentley.htm |
|
|
|
|
|
**************************************** |
|
Get volume 1 of the Experiment of the Week postings in book form! To order, |
|
send $9.95, plus $3.00 postage and handling to: |
|
|
|
Robert Krampf |
|
PO Box 60982 |
|
Jacksonville, FL 32236-0982 |
|
|
|
Include your e-mail address and I will notify you when I get your order. |
|
|
|
*************************** |
|
|
|
If you would like to be on the list, just send me an e-mail at [email protected], asking to be added to the Experiment of the Week List. |
|
|
|
Check out our web site at: |
|
http://www.krampf.com |
|
|
|
From Robert Krampf's Science Education Company |
|
4850 A1A South |
|
St. Augustine, FL 32084 |
|
(904) 471-4578 |
|
|
|
|