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METHODS OF SCIENCE
Early scientists did not know how to solve their problems. Often they did not study a
problem carefully. Many times they did not know what they were looking for. One of the most
important factors in good science is asking the right questions. Many discoveries made in the
last few hundred years are valid because the scientists who made them were good detectives.
What is Science?
The methods of science are unique. A scientist is a detective who must solve problems
by asking questions and putting the answers together in a meaningful and conclusive way.
Intelligent guessing is important to the scientist. But guessing alone is not enough. The guesses
must be supported or rejected by evidence.
Science is a process that produces a body of knowledge about nature. Areas of study
such as art, music, or history are no less scholarly than science because all of them involve
creativity. But, the manner in which science studies nature makes it different from other
subjects.
Science is carried out because people want to learn more about nature. Applying the
knowledge to real problems is technology (or applied science). For example, the science of
heredity can be used to solve real problems. Plants that make food and bacteria that produce
drugs have been produced. What practical problems have technological advances helped to
solve?
Scientists can solve problems in many ways. Each “case” is different. Usually certain
parts such as observation, interpretation, hypothesis formation, and experimentation are
included. The relative place of each of these in scientific investigation may vary. However, they
interact and are necessary in solving a problem.
Science is a particular way of investigating the world. Not all investigations are
scientific. For example, when you want to know how to get to Chicago from St. Louis, you do
not conduct a scientific investigation – instead you look at a map to determine a route. Making
individual decisions by applying a “map” of general principles is called deductive reasoning.
This type of reasoning is the reasoning of math, philosophy, politics, and ethics; it is the way in
which a computer thinks. For example, if this situation occurs, then apply this solution. If a car
is going too fast, applying the brakes slows it down. All of us rely on deductive reasoning by the
means of general principles to make everyday decisions.
How Scientists Work: Inductive Reasoning
How do scientists discover such general principles? Religious and ethical principles often have a
religious foundation; political principles reflect social systems. Some general principles,
however, come from observations of the physical world around us. They find them in stone and
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air and fire, in a butterfly’s wing and a tiger’s stare – in short, wherever they look in the world
around them. If you drop an apple, it will fall whether or not you wish it to, and despite any
laws you may pass forbidding it to do so. Scientists are, above all, observers: They look at the
world to understand how it works. From their observations, scientists determine the general
principles that govern our physical world.
This way of discovering general principles by careful examination of specific cases is
called inductive reasoning. Inductive reasoning first became popular about four hundred years
ago, when Isaac Newton, Francis Bacon, and others began to conduct experiments, and from
experiment results, to infer general principles about how the world operates. The experiments
were sometimes quite simple. Newton’s consisted simply of releasing an apple from his hand
and watching the apple fall to the ground. From this observation, Newton inferred a general
principle – that all objects fall toward the centre of the Earth. This principle was a possible
explanation or hypothesis.
Observation
Careful observation is very important to a scientist. No matter what the problem,
scientists must observe carefully all they can about it. Often this process includes reading what
is known already about the subject or related subjects. Careful and confirmed observations
become facts. A fact is something about which there is no doubt. It is a fact that this paper is
white.
In science, facts are often called data. Many data result from observations made during
experiments. Some data are descriptive; for example, the colour and shape of a tadpole. Other
data involve numbers; for example, measurements of the growth of the tadpole.
Scientists, worldwide, use a universal language of measurements and their symbols.
This is known as the International System of Measurement (SI – System d’Internationale –
French as it was determined in France). This the modern form of the metric system. It utilizes
the decimal system which is much easier than the imperial system that the US uses today. This
makes it much easier for information and data to be passed on from country to country.
Scientists must be careful to not overlook facts. This can easily happen with
investigations that take a long time as a person may become tired and become more willing to
accept certain errors and misjudgements to just get the investigation over with. Scientists must
have patience and they must know the importance of what they observe. Sometimes an
observation may seem unimportant but turns out to be valuable.
In 1928, the British scientist Sir Alexander Fleming made such an observation. He was
studying a certain type of bacteria, Staphylococcus in his laboratory. The bacteria were grown
in culture dishes. (Italicized words are the genus and species names) Fleming noticed that a
mold called Penicillium grew in some of the culture dishes. He might have thrown out the
dishes due to cross contamination, but he observed something else. Around the Penicillium
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was a clear zone. This area was clear because the bacteria that had grown there had died. This
only occurred in dishes that had Penicillium.
Interpretation
This brief discussion of Fleming’s discovery points out another important part of the
scientific procedures. Observing that bacteria were killed, Fleming reasoned that the mold
must be producing a chemical that killed bacteria. He assumed that the chemical spread from
the mold throughout the clear zone. He could not observe a substance either being produced
by the mold or killing the bacteria. But this idea was the most logical explanation he could
make of the observed facts.
Such reasoning is a key part of scientist’s investigations. They must be able to interpret
their observations of nature. These interpretations and explanations may not always be
correct. What may seem to be a logical explanation might turn out to be completely or partly
wrong. Just think about a movie in which you thought the ending was totally predictable and
then took the most dramatic turn to give an ending you never would have expected. However,
logical reasoning and interpretation are necessary to obtain a final answer to any specific
problem.
Formation of a Hypothesis
Facts have no meaning unless they can be tied together. A scientist must try to put
together the pieces as if working on a jigsaw puzzle without knowing what the total picture will
look like.
If a scientist gains insight into the problem, an idea can be developed that may fit the
pieces together. Such an idea or statement is called a hypothesis. The purpose of a hypothesis
is to relate and explain observed facts. Fleming’s reasoning about the action of Penicillium on
bacteria could be stated as a hypothesis. He thought that some chemical produced by
Penicillium kills certain bacteria.
A good hypothesis not only explains the facts but also predicts new facts. Besides
stating that a chemical killed the bacteria, Fleming also predicted that a certain chemical alone
(not the entire mold) should be able to kill the bacteria.
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Forming a hypothesis is not the end of the problem. Many early scientists failed because
they made a hypothesis their conclusion. A good hypothesis must be tested. Only through a
test can a scientist be certain a hypothesis is correct. A hypothesis is a “tool” for further study
of a problem. You see this every week on CSI. They must test every hunch that they have so
that they catch the correct criminal and avoid imprisoning the wrong person.
Scientists distinguish among hypotheses that are actually true and the many hypotheses
that might be true by systematically ruling out all of the incorrect hypotheses (those not
consistent with the observations). However, hypotheses that we are unable to disprove are
retained and are regarded as fact until they can be disproven. So Newton’s hypothesis that
every object falls to the centre of the Earth is regarded as fact until it can be disproven. But if
new evidence does come along, the hypothesis must be thrown out – that is what is great
about science – your whole world can change. This is why it is important in science to be open
to new evidence, to not get too hung up an idea. Again think about CSI.
Scientists test hypotheses by doing experiments. An experiment evaluates all the
alternative hypotheses. For example, you have two closed doors. There are four possibilities:
1.
2.
3.
4.
“There is a tiger behind the door on the left.”
“There is a tiger behind the door on the right.”
“There is no tiger behind either door.”
“There is a tiger behind both doors.”
A successful experiment eliminates one or more of the hypotheses. For example, to test
these you might open the door on the right and find that a tiger leaps out at you. Thus you now
know #3 is not correct. This did not show us which one was true, but rather which one was
untrue. There could still be a tiger behind the left door. So by rejecting each incorrect idea, we
can get closer to the correct idea.
Experimentation
Fleming had to isolate the substance he thought was killing the bacteria. Then he had to
test the prediction that the substance would kill the bacteria. To do this test, he transferred
some of the mold to nutrient broth solutions. Nutrient broth solutions contain the basic
ingredients needed for mold to grow and reproduce. Fleming assumed the mold would
produce a chemical that would flow into the liquid broth. After he added the chemical and
broth (minus the mold) to the bacteria, he observed that the bacteria were killed. Thus he
isolated the chemical and also verified the prediction of his hypothesis. The chemical alone
could kill the bacteria; the mold was not necessary. Has his hypothesis been proved beyond a
shadow of a doubt?
A scientist must be sure of the cause of a certain effect. Fleming, for example, believed
that the chemical broth killed the bacteria, but how could he be sure? Something in the broth
itself might have killed the bacteria. When a test of the broth alone showed that it did not kill
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the bacteria, the doubt was removed. His hypothesis was supported and he named the
chemical penicillin.
Scientists conduct their experiments in a carefully controlled manner. A controlled
experiment is one in which all factors are kept the same except the thing being tested. The
factor that is being tested is called the variable factor. So in this controlled experiment, there
are two types of tests being conducted. The first type is called the control group which is a
standard that the second group, the experimental group, is compared to. For example, you
want to test a new chemical that kills algae in water. Your control group will be the water with
algae and you will do nothing to it. Your experimental group will be the water with algae that
has had the chemical added. You would then compare the two to see if the chemical worked or
not.
Within an experiment there are three main types of variables at work. The control
variables are those that you always keep the same between the control and experimental
groups. These may include using the same amount of material, the same temperature, the
same amount of sunlight, the same soil or other environmental conditions for all test subjects
so there is consistency. So with the above example, your control and experimental groups will
both have water from the same location, the same amount of water, they will have the same
temperature, and sunlight and oxygen exposure. The independent variable is the factor that
you are voluntarily changing, such as adding the chemical to the above example. The
dependent variable is the factor that changes due to the independent variable, such as the
amount of algae after the chemical is added.
An experiment may show that a hypothesis is partly or totally wrong. When this occurs,
the facts must be looked at again and interpreted in some other way. “ "We can't solve problems
by using the same kind of thinking we used when we created them." (Albert Einstein). As a result, the
hypothesis may need to be changed or a completely new one formed. If a hypothesis is
changed, new experiments must be carried out. Finally, to be acceptable to other scientists,
the experiment that confirms a hypothesis must give the same results each time it is repeated.
This is referred to as verification.
Fleming’s work with penicillin arose by chance during other research and led to a major
practical breakthrough. Fleming realized the future use of penicillin as a drug and studied its
effect on many common disease causing bacteria. Thank goodness for that!
This example illustrates two important points. First, much scientific research is carried
on because of the natural curiosity of humans. They want to know the “hows” and “whys” of
the world. As a result, there have been many benefits, from microwave ovens to antibiotic
drugs. Fleming did not set out to discover a drug to cure bacterial infections, but when the
unexpected happened, he did not ignore it. Use of the drug in medicine came about only after
this accidental discovery.
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Second, scientific knowledge builds upon the foundations of previous findings. Once
penicillin was discovered and its value shown, widespread interest arose. A single important
finding led to many related discoveries.
The Scientific Method (based on inductive reasoning):
Observation/Question  Hypothesis (based on previous knowledge or research done)
 Experiment (testing the different hypotheses – a new experiment for each hypothesis –
includes the purpose, the materials, procedure and data collection)  interpretation 
conclusion which may become a theory once verified over and over.
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Theories
Hypotheses that stand the test of time, which means that their predictions have been
tested and never rejected, are called theories. Thus, Newton’s general principle that all objects
fall toward the centre of the Earth, is referred to as the theory of gravity. While theories are
the solid ground of science, there is no absolute truth in science, only varying degrees of
uncertainty. Future evidence could always cause a theory to be revised. Just as DNA
revolutionized crime scene investigation replacing other methods used to verify suspects.
Scientists’ use of the word theory is very different from that of the general public. To
scientists, a theory represents that of which they are most certain; to the general public, the
word theory implies a lack of knowledge or a guess. A theory is a hypothesis that is supported
by a GREAT deal of evidence. Some theories are so strongly supported that future rejection is
highly unlikely. Such as, the Sun will rise in the East tomorrow. A theory that is tested over and
over and is accepted at the most likely solution for that time and is doubted to be defeated any
time soon becomes a law.
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