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Exhibition date: September 5 - October 4, 1992

Key Ideas: Microscopy, Astronomy, History of Science, Senses, Vision, Perception

Most human beings are very visual creatures. We rely on our eyes to provide us with more vital information than any other sense. Scientists, too, rely on their vision and powers of observation to increase their knowledge of the structure and function of our universe. But even though our eyes are among the most highly developed of all the animals, they are actually quite limited. During this exhibit we will explore objects and events too small, too far away, too fast, or too slow for normal vision using some of the tools that scientists have created to help us "see" the "invisible." Come prepared to explore that which is Out of Sight, but moving into Mind.

You and your students will:
* explore "invisible phenomena" with the use of scientific tools and techniques.
* identify at least five technologies that aid in revealing the invisible.
* list a variety of reasons why an object or event is unseeable.
* determine the best methods for seeing or measuring "invisible" things.

* What things can you think of that exist but are invisible?
* How do you know they exist if they are invisible?
* How many "tools" do you use each day that have invisible components?
* How do you "see" something that happened yesterday? Last week? Last year? Ten years ago? Ten thousand years ago?
* How many things do you suppose exist that we don't know about just because we haven't been able to see them yet?
* How accurate are our technology-based conclusions about things we cannot see?

To help you apply the California Science Framework (1990), we have written the key words, or "big ideas," in boldface.

Our eyes respond to only a narrow portion of the electromagnetic spectrum. Electromagnetic (EM) spectrum refers to the range of types of electromagnetic waves. EM waves carry energy from one place to another; they can travel through empty space, air, or transmission lines of wire or glass. EM waves travel at the speed of light -- 186,000 miles/second. However, the length of the waves and their frequencies vary. Radio waves are the longest and gamma rays, the shortest.

Many of the limitations of our eyes stem from the structure of the eye itself. For example, we cannot see things that are smaller than about 1/300 of an inch (scale). This is because the receptor cells (also known as rods and cones), though small and densely packed, are still a certain distance apart. Also, an object must reflect enough light to trigger enough receptor cells to make sense to the brain. Likewise, as quick as they are, nerve impulses take time to travel. A receptor cell can only fire at a certain rate. Therefore, our eyes cannot keep up with very fast-moving objects and they appear blurred, if we see them at all. These limitations result in gaps in our vision both in time and space. Fortunately, our brains "fill in" the gaps, smoothing out the pictures that we see. Otherwise motion in the world might appear very grainy and jerky to us.

Over the years, scientists have developed tools that increase our range of vision. The telescope was one of the first such tools, brought about by people's desire to get a closer look at those beautiful points of light in the night sky they admired so much. The telescope started out in a very primitive way (just a collection of lenses and mirrors lined up in the proper way). The telescopes of today evolved from these first, hand-held telescopes into enormous machines that fill a four to five story planetarium allowing us to see much farther and much more clearly than ever before.

The tools have not always gotten larger as they have improved. Sometimes the patterns of change lead to smaller instruments For instance in studying and repairing the human body, scientists started by simply dissecting cadavers. Now we are able to see what is happening inside the body without making a single incision by way of techniques such as X-rays (part of the EM spectrum). sonagrams, electrocardiograms, catscans and fiber optic video cameras. It is amazing!

Some things that we know a lot about, we still have never truly seen. For example, if we want to study an ecosystem, we cannot simply sit in a meadow for an afternoon and expect to have "seen" the ecosystem. For complex systems and interactions, we often create models to help us understand what is happening in a system. Sometimes the model is three-dimensional, like a globe. Sometimes it is two dimensional, like a diagram. Today, scientists often create models using complex computer programs. There are even computer models to help predict and explain the flow of water around a single reed in an estuarine environment. Trying to understand that tiny portion of the ecosystem ultimately helps scientists to understand the ecosystem as a whole.

Materials:

* Blindfolds for half of your class
(These can be made with a pattern attached -- materials needed: heavy paper, scissors, a hole punch, string, hole reinforcers)

Action:

a. Lead a discussion of the myriad ways we use our eyes and how life would be different if we could not see. (If possible invite a blind person to the class.)

b. Have the children experience what it is like to be blind by blindfolding them for an hour or more. (This is just a suggested time. You may choose more or less time according to your students' age, interests and/or abilities. ) Half the class could be blindfolded while the other half are assigned buddies whom they are to help, thereby increasing sensitivity to blind people from two perspectives. The blindfolded period could include lunchtime, a walk outdoors, a work assignment, or some activity that involves the use of other senses.

NOTE: This activity may make some children feel quite uncomfortable or frightened. It should be undertaken in a supportive atmosphere. You should talk to the children about this proposed activity and make sure that their parents do not object. Children should be encouraged but not forced to wear their blindfolds for the duration of the activity.
c. Afterward have the students discuss or write about their feelings about the experience and ask them what kind of devices or tools might have made things easier.

Mind:

* What kinds of feelings did this activity produce in you?
* What are the advantages/disadvantages of being blind?

Materials:

* Paper and pencil for each student

Action:

a. Many things are not sensed because we are constantly on-the-go. Take the children to a place where they can be separated from each other by at least ten feet (outside, a multi-purpose room, etc.) Outlaw any talking to each other. Have the children sit quietly and record the things they see, hear, feel around them. You decide the time, but the longer, the better; at least 15 minutes would be recommended.
b. Afterward discuss as a class the things that were observed. Make a class list and see how many people sensed similar things. Try this activity for several days and you will see interesting changes in what the children observe.

Mind:

* How many things did you observe? Do you think you would have seen more if you had been out there longer?
* How did your list change over time? For instance, did you start out listing only what you could see and then start listing the things your other senses were sensing?

Materials:

* Microscope(s) -- or magnifying lenses
* Various items to examine under the microscope (onion skin, thin leaves, fibers of fabric, hair, torn paper, samples of dust or pond water, flakes of skin, etc.)

Action:

a. Have the students bring in and examine different items under the microscope or with lenses.
b. Have the children draw pictures of what they see. Discuss observations as a class.
NOTE: Microscopes are often difficult to master. Spend time explaining how they work, practicing focusing, etc. Remember patience!

Mind:

* What kinds of things can you see with the microscope that you could not see with your eyes?
* What kinds of things would you like to examine with a more powerful microscope?

Materials: None

Action:

Lead a brainstorming session about things that are invisible or very difficult to see. Think of things that are not only too small to be seen, but also too big, too fast, too slow, too far away in time, etc. You might even try categorizing your ideas.

Mind:

* What kinds of invisible things were the easiest to think of? Why do you think this was so?

Materials:

* Stories encouraging observation (mysteries like Einstein ...) or stories where people explore previously unseen worlds (for example: The Magic School Bus or James and the Giant Peach)

Choose and/or modify words or definitions to fit your needs and grade level.
1. Sense - one of the body's ways of getting information from the outside world; includes sight, hearing, taste, smell, and touch.
2. Cell - the "building blocks" of the body, the smallest unit of living material. In our bodies, different types of cells do different jobs. For example, nerve cells carry messages to and from the brain.
3. Prism - a triangular piece of glass used for separating white light into its component wavelengths which appear to us as colors.
4. Microscope - a tool used to see things that are too small to be seen with our eyes alone.
5. Telescope - a tool used to see things that are too far away to be seen well.
6. Electron - a part of an atom that orbits the nucleus; a fundamental particle of negative electricity.
7. Micro - a prefix indicating a small size.
8. Macro - a prefix indicating a large size.
9. Model - a miniature representation of an object used for study of the object or a collection of objects.
10. Ecosystem - an interdependent community in nature interacting and functioning as a unit.
11. Estuarine - describing a natural environment located at the wide lower course of a river into which the ocean tides flow.

"The Eyes of Science," (March, 1978). National Geographic.

Bodanis, Davis. (1986)The Secret House. New York: Simon & Schuster. (A book with lots of neat pictures; takes a tongue-in-cheek, but scientific look, at all the invisible activity that takes place in the average house.)
Morrison, Philip and Phylis. (1982) Powers of Ten. New York: Scientific American Books, Inc. (Examines the view of a scene from very far away to very close up. Based on the short film of the same name. Conveys the idea of order of magnitude.)
Macaulay, David. (1988) The Way Things Work. (A great book for getting inside of ordinary objects like T.V.'s, radios, telephones, etc. that many of us don't really understand. Super illustrations.)
Schwartz, David. How Much is a Million?
Dahl, Roald. James and the Giant Peach. (A classic story about a boy who shrinks and explores the imaginary, inner world of a peach.)
Cole, Joanna. The Magic School Bus. (Another classic story about a school bus ride through the human body.)
Brinner, B. (April, 1992) "Of Molecules and Models." Science Scope, 15(7). (An article with good background information about models of molecules.)
Boslough, J. (1985) Worlds within the atom. National Geographic, 167(5).
Sochurek, H. (1987) Medicine's new vision. National Geographic, 171(1).
Weaver, K. (1977) Electronic voyage through an invisible world. National Geographic, 151(2).
Amos, W.H. (1977) Unseen life of a mountain stream. National Geographic, 151(4).
Boraiko, A.A. (1979) Harnessing light by a thread. National Geographic, 156(4). (Describes the uses of fiber optics which are now widely in use.)
Hann, J. (1991) How Science Works. Pleasantville, NY: Reader's Digest Association, Inc. (A great resource for all science topics. Good illustrations and photography.)
Strongin, H. (1991) Science on a Shoestring. Menlo Pk., CA: Addison-Wesley Publishing Co. (Another good general science book.)
DeVito, A. (1989) Creative Wellsprings for Science Teaching. W. Lafayette, IN: Creative Ventures, Inc. (Good general science book.)
Science For Children: Resources for Teachers. (1988) National Science Resources Center. Washington, D.C: National Academy Press. (Fantastic sourcebook for teachers containing curriculum, book and location resource references.)
Video: The Invisible World, National Geographic Society, 60 minutes. (This was a televised special for general audiences. It once was available from Tower Video. It may also be available through county education offices. A shorter version, Worlds Within Worlds, is for grades 7-12 and is 23 minutes long.

An Explorit Science Center "Science Byte":Microbes and Me.

List of other Explorit Science Center TERPS