Scientific Models
What is a scientific model?
Scientists study all sorts of natural phenomena, from protons to planets, from
muscles to mastodons, from earthquakes to ecosystems. No matter what the
topic, scientific study often follows a similar path: make observations, look for
patterns in those observations, and develop and test possible explanations for
the patterns that are seen. The explanations they develop are called scientific
models.
How are scientific models used?
Models help scientists (and everybody else, too) to make sense of what we see
in the world around us. They help us to explain our observations. For example,
Galileo developed a model to explain the motion of objects in the sky, including
the rising and setting of the sun and moon. Today scientists are developing
models to explain the uncontrolled cell division in cancer cells, the causes of
diseases, and how of climate change works, to name just a few. In all of these
cases a model allows scientists to explain some observations.
In addition to explaining observations, models allow us to predict future
observations. For example, once you have a model of what causes a solar
eclipse, you can attempt to predict when they will happen. Models that explain
weather phenomena can be used to predict our future weather, including winds,
temperature, precipitation, storms, floods, and droughts. A variety of models
explain how our bodies work. Doctors and therapists use these models to
diagnose and treat diseases, and to predict the likely future health of their
patients.
Models often lead scientists to ask questions for further study. Often the
development of a model leads scientists to ask new questions relating to the
subject of the model. For example, when scientists discovered that some
important diseases are caused by bacteria, it was assumed that many other
diseases are also caused by bacteria, which led to the understanding (and cure)
of many more diseases. In this way, models have led to rapid advances in many
fields of science and technology, including the revolutions in genetics and
electronics that are happening today.
How are models communicated?
In order to communicate their models, these scientists represent them with
drawings, graphs, equations, three dimensional structures, or words, but the
scientific model is the idea itself. Tools like drawings and graphs are just ways of
communicating their ideas (models) to others. For example, when you looked at
the black box in 6th grade, you looked for patterns in your observations, and tried
to develop an explanation of how the box might work. Your idea of how the box
worked was your model. In order to communicate your idea to the other
scientists in your class, you used words, drawings and perhaps a threedimensional structure (your own working box). These, however, were
representations of your model.
Soon you will have a chance to be scientists yourselves: during the next several
weeks, you will be developing models to explain a number of genetic phenomena
such as how seeds that are round and wrinkled only have round peas for “kids.”
How do you decide whether a model is “right”?
A community of scientists may have more than one model to explain a given
phenomenon, just as many models were proposed to explain the observations
you made in your “black box.” Were all of these models equally valid?
To ask which model is “right” is the wrong question. Models are judged as to
whether or not they are “acceptable” or “useful”, but not whether they are “right”.
Judgment of the acceptability or usefulness of models is based on three factors:
1. Can the model explain all the observations or, as you may have
experienced, explain some, but not all?
2. Can the model be used to predict the behavior of the system if it is
manipulated in a specific way? For example, could your model predict when
water would come out of the box or what volume of water would come out?
3. Is the model consistent with other ideas we have about how the world works?
Any model needs to be realistic.
Our model of the structure of atoms involves subatomic (little) particles such as
protons, neutrons, and electrons. Many observations support this model even
though nobody has ever seen inside an atom to be able to tell whether this model
is “right” or not. It meets the three criteria above very well, and is very useful in
that it helps us to predict what happens in the chemistry of atoms.
It is entirely possible for more than one model to be accepted to explain the same
phenomena. It is not always possible to exclude all but one model. For
example, physicists have two very different models that explain observations of
light. One model describes light as a series of waves, and the other describes
light as particles called photons. Both models are useful and each helps to
explain different things about light. In the same way, more than one model of the
black box could be acceptable and useful, as long as they meet the three criteria:
1) agree with the observations, 2) could be used to make predictions, and 3)
goes along with what we know about how the world works (is realistic.)
Do scientific models ever change?
In 6th grade you developed a model to explain the workings of your black box.
Your model probably changed as you made new observations and exchanged
ideas with other groups. In the same way, scientists often change (or even give
up completely) models as they make more observations and as they exchange
ideas with other scientists. Just as you did, these scientists make changes in
order to make their models better fit the observations, better able to predict new
observations, or goes along with other knowledge.
Historically, many important scientific models have changed a great deal in light
of new data and new ideas. For example, at one time scientists thought that
human sperm contained a tiny, preformed person (a “homunculus”) and that the
human egg was mainly a source of food for the developing living thing. When
more advanced microscopes allowed closer observation of sperm and egg, this
model was given up. The current model- in which both egg and sperm contribute
traits to the future living thing- is better able to explain the observation that living
things inherit characteristics of both parents.
Summary
Models are useful tools for scientists as they try to make sense of the world
around us. Models help us to understand complicated things in the world and
they have been very valuable in the tremendous scientific and technological
advances that we have seen, including those in medicine, genetics, electronics
and engineering. Next time you get a vaccination, buy a CD, or ride in a car or
bus, consider the many scientific models that were involved in the development
of these technologies.
1. Models are ideas that scientists use to explain patterns that have been
observed in the world.
2. Models are judged to be acceptable or not based on how well they can
a. explain data,
b. predict future data
c. how they go along with what is already known about the world (be
realistic.)
3. Models are constantly being used to ask more questions about the world,
and when new data are gathered, models are revised or even discarded
altogether. Scientific knowledge does not stay the same, but is always
changing.