Canned Constellations

Developer:

Charles Scaife
Department of Chemistry
Union College
Schenectady, NY 12308



Grade Levels:

K through 8



Discipline:

Physical Science/Astronomy



Goals:

  1. Make your own constellation viewer by punching a constellation pattern into the bottom of a black 35-mm film canister.
  2. Learn to identify the patterns of various constellations.
  3. Learn to find these constellations in the night sky.



Background:

Many of the ideas for this experiment were described in WonderScience (1). Additional information was obtaint was described in WonderScience (1). Additional information was obtained from A Field Guide to Stars and Planets (2).

You donŐt need a telescope or even binoculars to be an amateur astronomer. You can see many stars with your own eyes. You simply need instead a clear night and a place sufficiently far from city or town lights to be able to see the starry night. You also need to wait briefly to let your eyes get accustomed to the dark. Moreover, you can more easily maintain your adaptation to darkness by covering the lens of your flashlight with red plastic. If you use binoculars, you see hte same right-side-up image as with your eyes. However, if you use a telescope, you usually see an inverted image.

Ancient people really used their imaginations to dream up an elaborate picture from the simple pattern of a few stars. Therefore, learning to recognize constellations takes a good imagination and lots of practice. One way to see what constellations look like without even going outside is to make your own constellation viewers. You can even use your constellation viewers to play a game to see who can name the most constellations.



Teacher's Notes:

Empty film canisters can be obtained very easily at no charge from almost any photograph development store. Take a plastic bag ith you because the store will give you more than you can imagine when you tell them about your project! Be sure to get black plastic film canisters, not the translucent plastic ones which let in too much light.



Materials:

1 Black plastic 35-mm film canister for each student

1 Pushpin for each student

Copies of the constellations that you want students to make [the reverse of the way they appear in the sky; six are available from the WonderScience article and are modified in this experiment with permission along with three from reference (2), but you can also make your own from reference (2)]

1 Pair of blunt-tip scissors for every four students

2 Rolls of household transparent tape

6 Marking pens



Explanation:

The surprise or discrepant event in this experiment occurs when students find that the pitch of sound from a bottle lowers when more water is added to the bottle played as a percussion instrument (tapped with a spoon) whereas the pitch rises when more water is added to the bottle played as a wind instrument (blowing air over the mouth). Obviously, different media must be vibrating to produce the sounds in order for this result to be exhibited. This evidence elicits many ideas and considerable discussion among students. When tapping the bottles, both the bottle and contents are vibrating, and the larger the mass of bottle and contents, the lower the rate of vibration, and the lower the pitch. When blowing over the mouth of the bottle, only the air column within the bottle is vibrating, and the longer the air column, the lower the rate of vibration, and the lower the pitch.



Questions:

1. What happens to the pitch when water is added to a bottle tapped with a spoon and played as a percussion instrument?

The pitch lowers as more water is added.

2. What happens to the pitch when water is added to a bottle as you blow over the mouth and play as a wind instrument?

The pitch rises as more water is added.

3. Why are the differences in Questions 1 and 2 observed?

Different media must be vibrating in the two cases. When tapping the bottles with a spoon, both the bottle and contents are vibrating. As more water is added to the bottle, the mass of bottle contents increases. A larger mass vibrates at a lower rate of vibration, and the pitch is lower. When blowing over the mouth of the bottle, only the air column within the bottle is vibrating. As more water is added to the bottle, the air column becomes shorter, there is less mass of air vibrating, at a higher rate of vibration, and the pitch is higher.



References:

  1. Janice Pratt VanCleave, Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound, Wiley, New York, NY, 1991, pp. 222-223; Ray Broekel, Sound Experiments, from A New True Book Series, Childrens Press, Chicago, IL, 1983, pp. 7-12.
  2. Janice Pratt VanCleave, Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound, Wiley, New York, NY, 1991, pp 216-217.
  3. WonderScience: Fun Physical Science Activities for Children and Adults to Do Together, volume 6, number 1, January, 1992, American Chemical Society/American Institute of Physics, Washington, D.C., pages 2-3.
  4. Terry Cash, Steve Parker, and Barbara Taylor, 175 More Science Experiments to Amuse and Amaze Your Friends, Random House, New York, NY, 1990, p. 36.
  5. Ray Broekel, Sound Experiments, from A New True Book Series, Childrens Press, Chicago, IL, 1983, pp. 32-35.
  6. Tik L. Liem, Invitations to Science Inquiry, 2nd ed., Science Inquiry Enterprises, Chino Hills, CA, 1987, (12.2) p. 294.
  7. Alfred E. Friedl, Teaching Science to Children: An Integrated Approach, 2nd ed., McGraw-Hill, New York, NY, 1991, pp. 97-98.



Procedure:

USING THE BOTTLES AS PERCUSSION INSTRUMENTS

Be very careful not to spill water during this experiment. Pour different amounts of water into three bottles so that the heights of water in the bottles are 0 centimeters (cm), and approximately 3 cm, 6 cm, and 9 cm. If you gently tap the side of each bottle about three-quarters of the way up the bottle where the rounded portion begins, do you think the sounds produced will be the same or different? How do you think they might differ? Try it by tapping the bottles gently with a spoon.

Arrange the bottles in a row from the bottle with the lowest pitch on the left to the bottle with the highest pitch on the right. What happens to the water level as you move toward higher pitch? Try to adjust the water levels in the bottles to obtain the pitches necessary to play Mary Had a Little Lamb. Work cooperatively on this effort, and talk about your ideas and make predictions before trying them. Each student should play one bottle. Were you able to do it?

USING THE BOTTLES AS WIND INSTRUMENTS

Using the present amounts of water in the bottles, predict what will happen if, instead of tapping each bottle with a spoon, you blow through a half straw across the top of each bottle. Do you think the sounds produced will be the same and in the same order, or different? How do you think they might differ? Try it by blowing through a half straw tipped slightly downward and held so that some air hits the lip of the bottle but most air passes over the mouth of the bottle. You should be able to produce the sound of a horn or whistle. What do you hear? Are you surprised at the result?

Arrange the bottles in a row from the bottle with the lowest pitch on the left to the bottle with the highest pitch on the right. What happens to the water level as you move toward higher pitch? Try to adjust the water levels in the bottles to obtain the pitches necessary to play Mary Had a Little Lamb. Work cooperatively on this effort, and talk about your ideas and make predictions before trying them. Each student should play one bottle. Were you able to do it? Discard your half straw in the waste container when you are finished.




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