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Scientific Method
Scientific method
The scientific method usually refers to
either a series or a collection of
processes that are considered characteristic of scientific investigation and
of the acquisition of
new scientific
knowledge.
Philosophers,
historians and
sociologists have found many ways to describe the scientific process. Often
when someone describes how they think science is done, they are describing how
they think science may be best or most reliably done. As a result, discussions
of scientific method are frequently partisan. Indeed, there are perhaps as many
methods of doing science as there are methodologists.
The enunciation of a scientific method by
Roger Bacon in the
thirteenth century described a repeating cycle of observation, hypothesis,
experimentation and the need for independent verification. This view, itself
inspired by an arab alchemical tradition not endorsed by christian
ecclesiastical authority, led to
Francis Bacon (in 1620 with the New Organon) laying down some
methods for identifying causation between phenomena. With these
articulations, unfounded speculation and analogical arguments began to be
replaced by consistent and logical methods of investigation.
It is common to speak as if a single approach of this type
were how scientists operate literally and all the time. Most
historians,
philosophers and
sociologists regard this perspective as naïve, and view the actual progress
of science as more complicated and haphazard. The actual course of scientific
progress is inseparable from the politics and culture of science; a single,
formal process cannot suffice either to explain or prescribe scientific
progress.
The question of how
science operates is important well beyond the academic community. In the
judicial system and in policy debates, for example, a study's deviation from
accepted scientific practice is grounds to reject it as "junk
science." Whether strictly formularizable or not, science represents a
standard of proficiency and reliability, and this is due at least in part to the
way scientists work.
The essential elements of the scientific method are
traditionally described as follows:
-
Observe: Observe or read about a phenomenon.
-
Hypothesize: Wonder about your observations, and
invent a
hypothesis, a 'guess', which could
explain the phenomenon or set of facts that you have observed.
-
Test
-
Predict: Use the logical consequences of your
hypothesis to
predict observations of new phenomena or results of new measurements.
-
Experiment: Perform
experiments to test the accuracy of these predictions.
-
Conclude: Accept or refute hypothesis
These activities do not describe all that scientists do. This
simplified method is useful for teaching, since it describes the way in which
scientists often think of themselves as acting.
This idealised process is often misinterpreted as applying to
scientists
individually rather than to the scientific enterprise as a whole. Science is
a social activity, and one scientist's theory or proposal cannot become accepted
unless it has been published,
peer reviewed, criticised, and finally accepted by the scientific community.
The scientific method begins with observation. Observation
often demands careful
measurement. It also requires the establishment of operational
definitions of measurements and other relevant concepts. Definitions are
not scientific hypotheses; they are not "falsifiable"; they are always
true or tautological. Definitions condense a number of ideas into a
single word or phrase. That being said, an observer's definition could differ
significantly from commonly understood concepts of a term, and still be correct.
Such a definition, however, would carry greater risk of being misunderstood.
These definitions are operational in that they may differ with the context of a
hypothesis, and they may be refined when the hypothesis is refined.
For example, the term "day" is useful in ordinary life and
its meaning may vary with the context. (Do we mean a 24 hour period or do we
mean the time between sunrise and sunset?) We don't have to define it precisely
to make use of it. In many sciences it is precisely 86,400 atomic seconds. In
studying the motion of the Earth, we may use two distinct operational
definitions: a
solar day is the time between two successive observations of the sun at
the same position in the sky; a
sidereal day is the time between two successive observations a specific
star sky at the same position. The length of these two kinds of day differs by
about four minutes.
Slight differences between operational definitions are often
important, as they are needed to make experiments precise enough to distinguish
subtle underlying phenomena. An example of this lies in choosing the appropriate
segmentation in the statistical analysis of data. Distinctions in operational
definitions can also reflect important conceptual differences: for example,
mass
and
weight are regarded as quite different concepts in science, but the
distinction is often ignored in everyday life.
To explain the observation, scientists use whatever they can
(their own creativity (currently not well understood), ideas from other fields,
or even systematic guessing, or any other methods available) to come up with
possible explanations for the phenomenon under study.
In the twentieth century
Karl Popper introduced the idea that a hypothesis must be
falsifiable; that is, it must be capable of being demonstrated wrong.
Paul Feyerabend argued against this position, providing examples of
falsified scientific theories that nevertheless had a vital role in the progress
of scientific understanding.
Of course, it is impossible for the scientist to be
impartial, considering all known evidence, and not merely evidence which
supports the hypothesis under development. But by submitting their theories for
peer review, scientists can at least make it more likely that the hypotheses
formed will be relevant and useful, or at least get others to agree with it.
In the extremely rare cases where no better grounds for
discriminating between rival hypotheses can be found, the bias scientists almost
always follow is the principle of
Occam's Razor; one chooses the simplest explanation for all the available
evidence, in whatever sense "simple" is chosen to be defined (is it that which
takes the fewest steps, or combines the smallest number of scientific facts, or
takes the fewest words to express, or is the easiest to understand, or is the
most predictable, or simply seems the most like common sense, or the average
person's idea of common sense, to the scientist(s) judging the model?)
A hypothesis must make specific predictions; these
predictions can be tested with concrete measurements to support or refute the
hypothesis. For instance, Albert Einstein's General Relativity makes a few
specific predictions about the structure of space-time, such as the prediction
that light bends in a strong gravitational field, and the amount of bending
depends in a precise way on the strength of the gravitational field.
Observations made during a 1919 solar eclipse supported the hypothesis (i.e.,
General Relativity) as against those of the other possible hypotheses which
predicted different results. (Later experiments confirmed this even further.)
Deductive reasoning is the way in which predictions are used to test a
hypothesis.
Probably the most important aspect of scientific reasoning is
verification: The results of one's experiments must be verified. Verification is
the process of determining whether the hypothesis is in accord with empirical
evidence, and whether it will continue to be in accord with a more generally
expanded body of evidence.
Ideally, the experiments performed should be fully described
so that anyone can reproduce them, and many scientists should independently
verify every hypothesis. Results which can be obtained from experiments
performed by many are termed reproducible and are given much greater
weight in evaluating hypotheses than non reproducible results.
Scientists must design their experiments carefully. For
example, if the measurements are difficult to make, or subject to observer bias,
one must be careful to avoid distorting the results by the experimenter's
wishes. When experimenting on complex systems, one must be careful to isolate
the effect being tested from other possible causes of the intended effect (this
results in a controlled experiment). In testing a drug, for example, it
is important to carefully test that the supposed effect of the drug is produced
only by the drug itself, and not by the
placebo effect or by random chance. Doctors do this with what is called a
double-blind study: two groups of patients are compared, one of which receives
the drug and one of which receives a placebo. No patient in either group knows
whether or not they are getting the real drug; even the doctors or other
personnel who interact with the patients don't know which patient is getting the
drug under test and which is getting a fake drug (often sugar pills), so their
knowledge can't influence the patients either.
Falsificationism argues that any hypothesis, no matter how
respected or time-honoured, must be discarded once it is contradicted
by new reliable evidence. This is of course an oversimplification, since
individual scientists inevitably hold on to their pet theory long after contrary
evidence has been found. This is not always a bad thing. Any theory can be made
to correspond to the facts, simply by making a few adjustments—called "auxiliary
hypothesis"—so as to bring it into correspondence with the accepted
observations. The choice of when to reject one theory and accept another is
inevitably up to the individual scientist, rather than some methodical law.
Hence all scientific knowledge is always in a state
of flux, for at any time new evidence could be present that contradicts
long-held hypotheses. A classic example is the explanation of light.
Isaac Newton's particle paradigm was overturned by the
wave theory of light, which explained diffraction, and which was held to be
incontrovertible for many decades.The wave paradigm, in turn was refuted by the
discovery of the
photoelectric effect. The currently held theory of light holds that photons
(the 'particles' of light) are both waves and particles; experiments have been
performed which demonstrate that light has both particle and wave properties.
The experiments that reject a hypothesis should be performed
by many different scientists to guard against bias, mistake, misunderstanding,
and fraud. Scientific journals use a process of
peer review, in which scientists submit their results to a panel of
fellow scientists (who may or may not know the identity of the writer) for
evaluation. Scientists are rightly suspicious of results that do not go through
this process; for example, the
cold fusion experiments of Fleischmann and Pons were never peer
reviewed—they were announced directly to the press, before any other scientists
had tried to reproduce the results or evaluate their efforts. They have not been
reproduced elsewhere as yet; and the press announcement was regarded, by most
nuclear physicists, as very likely wrong. Peer review may well have turned up
problems and led to a closer examination of the experimental evidence
Fleischmann, Pons, et al believed they had. Much embarrassment, and wasted
effort worldwide, would have been avoided.
There are no definitive guidelines for the production of new
hypotheses. The history of science is filled with stories of scientists
describing a "flash of inspiration", or a hunch, which then motivated them to
look for evidence to support or refute their idea.
Michael Polanyi made such creativity the centrepiece of his methodology.
The anecdote that an apple falling on
Isaac Newton's head inspired his theory of gravity is a popular example of
this (there is no evidence that the apple fell on his head; all Newton said was
that his ideas were inspired "by the fall of an apple.")
Kekule's account of the inspiration for his hypothesis of the structure of
the
benzene-ring (dreaming of snakes biting their own tails) is better attested.
Scientists tend to look for theories that are "elegant"
or "beautiful";
in contrast to the usual English use of these terms, scientists have a more
specific meaning in mind. "Elegance" (or "beauty") refers to the ability of a
theory to neatly explain all known facts as simply as possible, or in a manner
consistent with
Occam's Razor.
The
Ptolemaic model of the universe suggested that the earth is the centre of a
pristine, perfect universe, and all motions in such a universe must be circular.
The model explained the apparent retrograde motion of the planets, by
introducing epicycles.
Nicolaus Copernicus' model placed the sun at the centre of planetary motion,
but also assumed that the planets moved in perfect circles. It also found it
necessary to make use of epicycles, and was as complex as, yet less accurate
than the heliocentric model. Improvement in the accuracy of the model depended
not only on developing the mathematics of elliptical orbits, but a conceptual
change in the way in which motion was understood.
Tycho Brahe made unprecedentedly accurate observations, but did not reject
the geocentric model. It took
Kepler 20 years to formulate equations which explained Tycho Brahe's
observations in heliocentric terms.
Isaac Newton's System of the World unified Kepler's laws and
Galileo's mechanical studies of acceleration, which re-integrated modern
science into a comprehensible world model.
Dogged adherence to method can be counterproductive.
History is replete with examples of accurate theories ignored
by peers, and inaccurate ones propagated unduly.
Often it is the less accurate theory that eventually becomes
accepted.
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