Models, Scientific and Otherwise, and Theories

Can you name some models? Model cars Model of the globe Model of the solar system (orrery) Model of the human skeleton Model of the skin Model of the brain Model of Earth’s crust

How do we use these models? Learn the parts of a whole Help us visualize something very large, very small, and/or complex Help us visualize hidden (internal) structures Help us visualize relationships among parts For explanation and teaching Are scientific models different from these types of models?

Scientific models When the data support a hypothesis, scientists usually try to explain the phenomena or system they are studying by constructing a model. A model in science is more than a physical object or mental picture; it is an explanation of how phenomena occur (a mechanism) and how data or events are related. It is a representation of a system or phenomenon. It is dynamic, not static. It can be visual, verbal, or mathematical.

Why Use Scientific Models? Do scientists use models in the same way? They can, for basic explanation and description (skin, brain, globe), but they more often use models that can be modified as their understanding of a system or phenomenon grows, through the practices of (1) designing experiments, (2) collecting data, (3) analyzing their results, (4) discussing and interpreting evidence, and (5) communicating their findings to others.

Scientists Using Models Scientists typically use models to Study extremely complex systems, for example, Earth’s climate which has many factors that are dependent on one another. Such a system is impossible for scientists to work with as a whole. Study extremely small or extremely large systems Make predictions Compare outcomes among competing models Test out ideas that would be impractical (too expensive, too large) or impossible (inaccessible, back in time) otherwise

Models and Theories If a model is very successful at explaining many phenomena, it may become part of a theory, a broad generalization that explains a body of facts or phenomena. Can you think of some models that have become theories?

Benefits of Using Models Allow us to test, evaluate, and revise as much as we need Can be much simpler than the system or phenomenon being studied Can be manipulated and adjusted far more easily than a real system. Can allow us to ‘slow down’ a process so we can better understand what is happening. Can show how a system changes over time, extending our knowledge into the future (predictions). Can allow for safe testing of an idea or event under controlled circumstances Can be far cheaper than running actual tests

Drawbacks of Using Models Can be overly simplified to the point of not being very useful Often leave out important aspects or factors so that results aren’t realistic Are always less reliable than direct measurements would be

Types of Models Physical replicas that are 3-D representations (brain, skin layers, toy car) Conceptual: Drawings or diagrams that represent one’s current conceptual understanding about how a specific natural system behaves (atomic theory, plate tectonics) Mathematical Equations (electricity and magnetism, relativity) Computer simulations (formation of the moon, asteroid impact) Flow charts (business models) Graphs

Model Success How do scientists evaluate the success of a model? Can the model explain most or all of past observations? Can the model be used to predict the happenings of the system or event if it is manipulated in a specific way? Is the model consistent with other ideas we have about how the world works? Is it cost effective?