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the elements are and the concept of the nature of atoms have even be involved in all three activities. Some, for example, might
changed over time, but the ideas first came from ancient natural spend all of their time out in nature, “in the field” collecting data
philosophers. and generalizing about their findings. This is an acceptable means
of investigation in some fields of science. Other scientists might
spend all of their time indoors at computer terminals develop-
THE SCIENTIFIC METHOD ing theoretical equations to explain the generalizations made by
Some historians identify the time of Galileo and Newton, ap- others. Again, the work at a computer terminal is an acceptable
proximately three hundred years ago, as the beginning of mod- means of scientific investigation. Thus, many of today’s special-
ern science. Like the ancient Greeks, Galileo and Newton were ized scientists never engage in a five-step process. This is one
interested in studying all of nature. Since the time of Galileo and reason why many philosophers of science argue that there is no
Newton, the content of physical science has increased in scope such thing as the scientific method. There are common activities
and specialization, but the basic means of acquiring under- of observing, explaining, and testing in scientific investigations in
standing, the scientific investigation, has changed little. A scien- different fields, and these activities will be discussed next.
tifi c investigation provides understanding through experimental
evidence as opposed to the conjectures based on the “thinking
only” approach of the ancient natural philosophers. In chap- EXPLANATIONS AND INVESTIGATIONS
ter 2, for example, you will learn how certain ancient Greeks Explanations in the natural sciences are concerned with things
described how objects fall toward Earth with a thought-out, or events observed, and there can be several different ways to
or reasoned, explanation. Galileo, on the other hand, changed develop or create explanations. In general, explanations can
how people thought of falling objects by developing explana- come from the results of experiments, from an educated guess,
tions from both creative thinking and precise measurement of or just from imaginative thinking. In fact, there are even several
physical quantities, providing experimental evidence for his examples in the history of science of valid explanations being
explanations. Experimental evidence provides explanations to- developed from dreams.
day, much as it did for Galileo, as relationships are found from Explanations go by various names, each depending on the
precise measurements of physical quantities. Thus, scientific intended use or stage of development. For example, an expla-
knowledge about nature has grown as measurements and inves- nation in an early stage of development is sometimes called a
tigations have led to understandings that lead to further mea- hypothesis. A hypothesis is a tentative thought- or experiment-
surements and investigations. derived explanation. It must be compatible with observations
What is a scientific investigation, and what methods are and provide understanding of some aspect of nature, but the key
used to conduct one? Attempts have been made to describe word here is tentative. A hypothesis is tested by experiment and
scientific methods in a series of steps (define problem, gather is rejected, or modified, if a single observation or test does not fit.
data, make hypothesis, test, make conclusion), but no single de- The successful testing of a hypothesis may lead to the design
scription has ever been satisfactory to all concerned. Scientists of experiments, or it could lead to the development of another
do similar things in investigations, but there are different ap- hypothesis, which could, in turn, lead to the design of yet more
proaches and different ways to evaluate what is found. Overall, experiments, which could lead to. . . . As you can see, this is a
the similar things might look like this: branching, ongoing process that is very difficult to describe in
specific terms. In addition, it can be difficult to identify an end-
1. Observe some aspect of nature.
point in the process that you could call a conclusion. The search
2. Propose an explanation for something observed.
for new concepts to explain experimental evidence may lead
3. Use the explanation to make predictions.
from hypothesis to new ideas, which results in more new hy-
4. Test predictions by doing an experiment or by making
potheses. This is why one of the best ways to understand scien-
more observations.
tific methods is to study the history of science. Or do the activity
5. Modify explanation as needed.
of science yourself by planning, then conducting experiments.
6. Return to step 3.
The exact approach used depends on the individual doing the Testing a Hypothesis
investigation and on the field of science being studied. In some cases, a hypothesis may be tested by simply making
Another way to describe what goes on during a scientific some simple observations. For example, suppose you hypoth-
investigation is to consider what can be generalized. There are at esized that the height of a bounced ball depends only on the
least three separate activities that seem to be common to scien- height from which the ball is dropped. You could test this by
tists in different fields as they conduct scientific investigations, observing different balls being dropped from several different
and these generalizations look like this: heights and recording how high each bounced.
Another common method for testing a hypothesis involves
• Collecting observations
devising an experiment. An experiment is a re-creation of an
• Developing explanations
event or occurrence in a way that enables a scientist to support
• Testing explanations
or disprove a hypothesis. This can be difficult, since an event can
No particular order or routine can be generalized about be influenced by a great many different things. For example, sup-
these common elements. In fact, individual scientists might not pose someone tells you that soup heats to the boiling point faster

14 CHAPTER 1 What Is Science? 1-14