Science Bytes

Writing on the Science Bytes pages is copyrighted. It is for you to read, not take. You may not publish or distribute it electronically or in hard copy without written permission from Explorit or other cited copyright owner. The material is here for your entertainment or edification - you may of course pass the URL to whom ever you wish.


by Suzanne Ullensvang (1995)
Change Your Mind?

"Changes. Time may change me but I can't change time."
David Bowie, "Changes"

I woke up listening to a song on the radio about change and time. Change seems to be everywhere. The days are getting shorter, leaves have fallen, an old metal lawn chair is rusting in my backyard...

Can you think of anything in the world that is not changing -- a rock, a mountain, the sun? Even the things that appear static are changing in ways that we may not be able to perceive directly.

While it's true that we can't stop time or halt the changes that accompany the passage of time, we can try to recognize and understand the physical and biological processes that are changing the world around us.

The study of change is fundamental to all scientific disciplines. What happened to the dinosaurs? Will certain chemicals react with each other? Can we slow down the aging process? The questions that scientists ask are questions about how entities and systems change. By observation, investigation, and experimentation, we can discover processes of change and sometimes find recognizable trends or patterns in change.

Change occurs on many different scales of time and size. You can see the change that occurs when you cook an egg. Similarly, you can personally experience the changes in your body as you grow and age. Exploring other changes often requires indirect evidence. To a geologist, layers of rock laid down over millions of years tell a story of what the Earth may have been like in the past. To a paleontologist, fossils offer subtle clues about earlier life forms and suggest ideas of how species may have changed over many generations.

What are some examples of dynamic processes causing change in the world around us?

Changes in the Earth's Crust:
Terra firma is not as firm as it seems. The surface of the Earth is composed of plates of thick bedrock that are continually shifting. Earthquakes and volcanic eruptions are sudden and dynamic reminders of the activity of the Earth's crust. Usually, however, the adjustments in the crust take place very slowly on a massive scale as regions of the Earth rise, tilt, or subside. Perhaps you have heard that California is slowly slipping into the ocean; this change is due to tectonic movement of the plates.

Changes in the Earth's Landscape:
Where rocks are exposed on the surface they are broken down by weathering. Rain, ice, windblown sand, and even tree roots can physically break rocks apart into smaller and smaller particles. Some types of rocks, such as limestone, are also dissolved by the action of water or other chemicals. At the same time that surface rocks are decomposing, heat, pressure, cooling, and/or chemical activity in the right combination act to form new rocks at or below the surface of the earth. Next time you look at the Sierras, remember that they are engaged in an active cycle of geologic change.

Changes in Organisms:
The life cycle of a plant or animal is the progression from its formation to its death. We all have direct experience with the human cycle of birth, growth and death. The life cycles of many other organisms have characteristics that are very different. Butterflies and some other insects go through a complete metamorphosis in which they transform from one body form and lifestyle into completely different ones. Although the details of how an organism changes may be influenced by factors in the environment, the general pattern of life changes is programmed within each organism's DNA, the set of chemically coded instructions contained in the cells.

Changes in Species:
The chemical code that guides the life cycle of living things is passed on through generations. Changes can occur randomly as mutations in the DNA, that result in new combinations of codes that are passed from parents to offspring. In each generation, some individuals in a species may be better suited to survive and reproduce in their particular environment. They are most likely to pass along their DNA to future generations and perpetuate the beneficial traits that helped them survive. Natural selection is the term used by scientists to describe this process of change within a species.

What other processes of change can you identify in our natural world? There are many and they are ultimately all interconnected.

Projects to Try at Home

Observe an enzyme in action.
Enzymes are proteins which speed up chemical reactions. For example, saliva contains an enzyme which breaks down starches in food. To demonstrate this, chew a soda cracker well and hold it in your mouth for 5 minutes.

What happens? (Amylase is the enzyme at work here; it turns starch into sugar.)

More enzyme action.

You will need an apple, a knife, wax paper, a spoon, and a vitamin C tablet. Use the spoon to crush the tablet onto the wax paper.

Cut the apple in half with the knife.

Sprinkle the crushed vitamin C over one apple half. Allow the apple sections to sit uncovered for at least an hour.

Observe both apple pieces. (Enzymes cause the untreated apple to discolor and turn brown. Vitamin C reacts with the enzymes and prevents the discoloration.)

Rusty Rock

Demonstrate how oxygen causes a rock to crumble. You'll need steel wool without soap (found in the paint department), a saucer, and some water.

Place a piece of steel wool about the size of a lemon in the saucer.

Moisten the steel wool with water.

After 3 days, pick up the steel wool and rub it between your fingers. (You may want to wear a rubber glove to avoid steel splinters.)

Do you see that parts of the steel wool have turned into a red powder? (Oxygen combines with the iron in the steel wool pad, forming iron oxide or rust. Rocks with yellow, orange, or reddish-brown streaks usually contain iron. The iron at the surface of the rock forms iron oxide when exposed to moist air, and eventually crumbles away as did the steel wool.

Shape the land

Demonstrate how the rocks are shaped by abrasion. You will need a fingernail file and a six-sided pencil.

Rub the file back and forth across the ridges on the pencil. Observe the surface of the pencil.

You will see that the ridges are broken down. (The file has a rough, grainy surface. Tiny pieces are cut from the pencils as the file moves back and forth across it. Surfaces can be pitted and polished by sand grains carried by wind. The grains of sand act like the file as they strike and cut away surfaces. This type of erosion is called abrasion.)

Send feedback to
Explorit Science Center
P.O. Box 1288, Davis, CA 95617, USA
Phone: (530)756-0191     Fax: (530)756-1227