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Stability and Chance

In both natural and built systems, stability and change are an important focus of study for both scientists and engineers. Stability refers to a system that is unchanging. However, stability does not mean that a system is completely static. A stable system may experience a small disturbance, but return to its stable state. Equilibrium is a stable state, whether static or dynamic. In static equilibrium, an object is at rest and all of the forces are balanced, as with a book sitting on a flat table. A dynamic equilibrium exists when chemical reactions or physical movements occur at rates that balance out, creating no net change in a system. For example, a lake will remain at a constant volume if the flow of water out of the lake is equal to the flow of water into the lake. A cyclic pattern can also be considered a stable condition. For example, as the Earth rotates, a steady pattern of day and night occurs. Change and stability are interpreted relative to each other and over given time scales. A system may be stable on a short time scale, but change over a long time scale. For example, over the course of a day, a juvenile fish may not change much, but over the course of a few months, it will grow into an adult. Across disciplines, models are often used to make sense of stability and change in different systems.

 

<p><strong>Fig. 2.19.</strong> A National Oceanic and Atmospheric Administration (NOAA) buoy used to detect changes in wave height. This buoy is used to monitor tsunami activity.</p><br />

In marine and aquatic science, stability and change are studied in a variety of contexts. For example, scientists may be interested in how an event like an earthquake triggers a tsunami, which then travels across the ocean and affects coastal areas (Fig. 2.19). This chain of events represents a series of stability and change, as something happens that causes a reaction and then systems return to stability. Other scientists study how human activities impact natural systems, such as how burning fossil fuels leads to increased carbon dioxide in the atmosphere, which leads to an increase in the temperature of Earth’s land and ocean. Physiologists study how organisms like beluga whales maintain their temperature and fluid levels within narrow boundaries. These types of feedback systems can be interpreted through a lens of stability and change. Ocean engineers also consider the concepts of stability and change when designing solutions to problems. For example, engineers may want to create materials or methods to prevent a bridge from rusting or cracking, or they may wish to physically change the entrance to a boat harbor so that boats can pass more easily.

 

The framework suggests that stability and change can be recognized by young children in common situations, such as building with blocks or watching a pet grow. Teachers can help students develop language to describe these concepts and guide students to ask why some things change and other things remain the same. As students progress through the grades, they can apply the concept of patterns and scale to their observations of stability and change. Students’ understanding of stability and change should become more nuanced over time as their understanding of more complex systems and rates of change over time grows.

 

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.