Science, Matter, and Energy - Environmental Science - page 21

We often hear about the scientific method. In reality,
many scientific methods exist: They are ways scien-
tists gather data and formulate and test scientific hy-
potheses, models, theories, and laws.
Many variables or factors influence most processes
or parts of nature scientists seek to understand. Ideally,
scientists conduct a controlled experiment to isolate and
study the effect of a single variable. To do such a single-
variable analysis, scientists set up two groups. In the ex-
perimental group, the chosen variable is changed in a
known way. In the control group, the chosen variable is
not changed. If the experiment is designed properly,
any difference between the two groups should result
from a variable that was changed in the experimental
group (see Science Spotlight, below).
A basic problem is that many of the phenomena
environmental scientists investigate involve a huge
number of interacting variables. This limitation is
sometimes overcome by using multivariable analysis —

Ask a question

Do experiments
and collect data

Interpret data

Well-tested and
accepted patterns
in data become
scientific laws

Formulate hypothesis
to explain data

Do more experiments
to test hypothesis

Revise hypothesis
if necessary

What Is Harming
the Robins? Well-tested and

accepted
hypotheses
become
scientific theories

Suppose a scientist observes an
abnormality in the growth of
robin embryos in a certain area.
The area has been sprayed with a
pesticide, and the scientist sus-
pects this chemical may be caus-
ing the abnormalities.
To test this hypothesis, the scientist carries out a
controlled experiment. She maintains two groups
of robin embryos of the same age in the laboratory.
Each group is raised with the same conditions of
light, temperature, food supply, and so on, except
that the embryos in the experimental group are ex-
posed to a known amount of the pesticide.
The embryos in both groups are then examined
over an identical period of time. If the scientist
finds a significantly larger number of the abnor-
malities in the experimental group than in the con-
trol group, the results support the idea that the pes-
ticide is the culprit.
To be sure no errors occur during the proce-
dure, the original researcher should repeat the
experiment several times. Ideally, one or more
other scientists should repeat the experiment
independently.

Figure 2-2 What scientists do.

SCIENCE
SPOTLIGHT

nomena that have a high degree of certainty because
they are supported by extensive evidence.
Nonscientists often use the word theory incorrectly
when they actually mean scientific hypothesis, atentative
explanation that needs further evaluation. The state-
ment, “Oh, that's just a theory,” made in everyday con-
versation, implies a lack of knowledge and careful test-
ing—the opposite of the scientific meaning of the word.
Another important result of science is a scientific,
or natural, law: a description of what we find happen-
ing in nature over and over in the same way. For ex-
ample, after making thousands of observations and
measurements over many decades, scientists discov-
ered the second law of thermodynamics. Simply stated,
it says that heat always flows spontaneously from hot
to cold—something you learned the first time you
touched a hot object. Scientific laws describe repeated,
consistent findings in nature, whereas scientific theo-
ries are widely accepted explanations of data and laws.
A scientific law is no better than the accuracy of
the observations or measurements upon which it is
based. But if the data are accurate, a scientific law can-
not be broken.

Critical Thinking

Can you find flaws in this experiment that might
lead you to question the scientist's conclusions?
( Hint: What other factors in nature—but not in the
laboratory—and in the embryos themselves could
explain the results?)

Scientific Method
There are many scientific methods.