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Scientific method

The scientific method is the way scientists investigate the world and
produce knowledge about it. Colloquially the term usually refers to an
idealized, systematic approach that is supposed to characterize all
scientific invetigation. It is distinguished from other routes to knowledge
by its use of controlled experiments and its requirement that results be
reproducible. Many scholars do not believe in the existence of such a
method, however, or they do not believe that it accurately describes
science. The actual methods of scientists, they argue, are less ideal and
more haphazard.

The question of how science operates is not only academic. In the judicial
system and in policy debates, a study's deviation from accepted scientific
practice is grounds to reject it as "junk science." Whether they are
diagnosing a patient, investigating a murder or researching a social trend,
non-scientists cite "the scientific method" as a paradigm. Methodical or
not, science represents a standard of proficiency and reliability.

A summary of the scientific method

Contray to popular belief, there is no method that scientists precisely
follow as one would follow an algorithm. However, there is more or less a
well-defined model that describes how science operates. It comprises these
steps:

   * 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.
   * Predict: Use the logical consequences of your hypothesis to predict
     observations of new phenomena or results of new measurements.
   * Verify: Perform experiments to test these predictions, to find just
     which prediction occurred.
   * Evaluate: Search for other possible explanations of the result until
     you can show that your guess was indeed the explanation, with
     confidence.
   * Publish: Tell others of your results. Other scientists can then review
     your reasoning and see if they can also repeat the result. This is
     known as peer review.

These steps are repeated continually, building a larger set of well-tested
hypotheses to explain more and more phenomena. These steps are not
necessarily always followed in the pattern shown above. For example,
theoretical physicists often develop multiple new hypotheses before
selecting which phenomena to observe.

Do scientists really follow the scientific method?

As stated above, there is no one "scientific method" that all scientists
follow as an algorithm. Science allows for creativity, genius, inspiration
and new ideas to enter at any stage in the scientific process. What
differentiates science from non-science is that such creativity is tested
against experimental reality.

There are no 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. 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 Ockham's Razor.

In 1962 Thomas Kuhn published his essay The Structure of Scientific
Revolutions, a seminal work on the practice and process of science. Kuhn
suggested that sociological mechanisms significantly affect the rejection of
older scientific theories and the acceptance of new ones. According to Kuhn,
when a scientist encounters an anomaly that is not explained by the
scientific community's currently accepted general paradigm or theory, that
community can ignore it (the increasing problems with Ptolemaic epicycles in
accounting for the motion of the planets was a long standing case), but is
often compelled to accommodate it by either modifying the existing theory or
replacing it with a new one. A paradigm shift occurs when a new paradigm
gains wider acceptance than a pre-existing one. It is at this point that
sociological factors may partly influence that abandonment. Kuhn postulates
that "normal science" continues on after the adoption of a new paradign,
punctuated with occasional scientific revolutions as later anomalies arise
and paradigm shifts occur.

The typical example used in Kuhnian explanations is the development of
astromonical theory that began, more or less, with the Aristotelian model of
the universe: "The earth is the center of a pristine, perfect universe," and
all motions in such a universe must be circular. The Aristotelian model was
afflicted with various anomalies, such as the apparent retrograde motion of
the planets, which were accomodated by modifications of the model. Nicolaus
Copernicus's model differed by placing the sun at the center of planetrary
motion. Both Kepler and Galileo found evidence that supported the
heliocentric model. Aristotle's laws were replaced by Isaac Newton, and
eventually by Albert Einstein's General Relativity. This example
demonstrates that much time may pass before a substitute paradigm is widely
accepted. The Aristotelian model dominated Western thought for more than
2000 years before Newton's viewpoint took its place.

Late 20th century study on the scientific method has focused on
quasi-empirical methods, such as peer review, the spread of notations, which
are the key common concern of philosophy of science, and the philosophy of mathematics.

History is replete with examples of accurate theories ignored by peers, and
inaccurate ones propagated unduly, due to social factors. The establishment
of "official" scientific doctrine in the former Soviet Union is a case in point.

Scientists differ on how 'real' their models of reality are - the
traditional concern of philosophy of science itself. Some writers
(non-scientists) involved with deconstructionism adopt a position of extreme
skepticism, and argue that no empirical methods can validate any given
theory, and therefore all of science must be seen as quasi-empirical. They
argue that science is just a social construction; it is only a way that
human cultures come to agree on facts, notations, and predictions.

History of the scientific method

The earliest foundations of the scientific method are often credited to
Roger Bacon in England and Galileo Galilei in Italy. Later contributions by
Francis Bacon, Rene Descartes and others have added to the understanding of
scientific method. Some historians of science believe that the scientific
method was actually developed centuries earlier, in the Islamic world. See
The experimental method in the Islamic World (article in progress).

For more on this topic, see the articles on the History of Science and
Technology, and the philosophy of science.

The scientific method in detail

Observation

The scientific method begins with observation. Observation demands careful
measurements.

Scientists use operational definitions of their measurements; measurements
are defined in terms of physical actions that can be performed by anyone,
rather than being defined in terms of abstract ideas or common understanding.

For example, the term "day" is useful in ordinary life and we don't have to
define it precisely to make use of it. But in studying the motion of the
Earth, you have to define the words you use very precisely; science makes
two operational definitions of a day: a solar day is the time between
observing the sun at a particular position in the sky and observing it in
the same position the next time; a sidereal day is the time between
observing a specific star in the night sky at a specific position, and that
same observation made the next time. These two different definitions are
important since they are slightly different.

Hypothesis

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. The most important
aspect of an explanation (ie, an hypothesis) is that it must be falsifiable,
that is, capable of being demonstrated wrong.

The scientist should also be -- but need not be and often is not --
impartial, considering all known evidence, and not merely evidence which
supports the hypothesis under development. This makes it more likely that
the hypotheses formed will be relevant and useful and not subject to
external bias and distortion.

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.

Prediction

A hypotheses 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 many 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 of a 1919 solar eclipse supported the hypothesis (ie,
General Relativity) as against all other possible hypotheses which did not
make such a prediction. (Later experiments confirmed this even further.)

Deductive reasoning is generally used to develop predictions used to test a hypothesis.

Verification

Probably the most important aspect of scientific reasoning is verification:
The results of one's experiments must be verified.

This is both useful as a practical matter (e.g., in chemical engineering or
planetary exploration), but have sometimes demonstrated previously unknown
variations from currently accepted theory (e.g., the CPT experiments of Yang
and Lee in the 1950s which forced fundamental changes in much of particle
physics). 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 multiple scientists 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.

"Verification" may be a misleading word, in that we don't really "confirm"
or "verify" a hypothesis so much as we fail to refute it.

Evaluation

Any hypothesis, no matter how respected or time-honored, must be discarded
once it is contradicted by new reliable evidence. Hence all scientific
knowledge is always in a state of flux, for at any time new evidence could
be presented 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. Proper peer review would
have, most likely, 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.

Peer review and documentation

The disclosure and documentation of experimental and observational methods
is of the utmost importance. These are what makes it possible for others to
attempt to reproduce the observations independently. Failure to disclose
methods and techniques has led to several famous scandals as with Paul
Kammerer's discredited work with toads. Such discipline is even more
important when the evidence being presented or the hypothesis being
supported have not been previously reported. The person who presents
undocumented original material risks having his work peremptorily dismissed
without any further consideration.

Criticisms of the scientific method

In any description of the scientific method, key themes of empiricism, that
is knowledge based on observation, and rationalism, that is knowledge based
on deductive reasoning, become apparent. (See Philosophy of science). It is
often stated that the natural sciences in our society owe their success to
the diligent application of the scientific method. Its proponents claim that
it is rational and logical. However, as in all areas of human endeavor,
there is some debate as to its nature and utility. Proponents of the
scientific method caricature its detractors as ultra-relativists, whereas
some detractors caricature proponents as positivists, and consider that the
scientific method does not adequately explain the success of science in our society.

Imre Lakatos showed how people studying the natural world have, throughout
the ages, constructed historical accounts to suit their pet philosophies and
methods. This "rational reconstruction" of the history of science is then
used to justify certain ideological assumptions, producing what might
tentatively be called a mythology of science. Like Kuhn's arguements, this
is essentially a sociological or psychological observation about the
practice of actual scientests, not an inherent feature of science apart from
some of its practicioners.

The philosopher Paul Feyerabend argued that descriptions of the scientific
method often do not match how scientific discoveries have actually occurred
in history. Feyerabend objected to any single prescriptive scientific method
on the grounds that science has no single aim. Without a fixed ideology, or
the introduction of religious tendencies, the only approach which does not
inhibit progress (using whichever definition of progress you see fit) is
"anything goes": "'anything goes' is not a 'principle' I hold [...] but the
terrified exclamation of a rationalist who takes a closer look at history."
(Feyerabend, 1975).

Feyerabend's criticisms have been used by some to argue that science does
not tend toward the truth, that it has no advantage over other ways of
examining the world, and that its intellectual output largely is a
socio-historical accident of the culture and values of scientists.
Feyerabend himself strongly opposed this conclusion:

     "How can an enterprise {science} depend on culture in so many ways, and
     yet produce such solid results? ....Movements that view quantum
     mechanics as a turning-point in thought - and that include fly-by-night
     mystics, prophets of a New Age, and relativists of all sorts - get
     aroused by the cultural component and forget predictions and
     technology." (Source: Paul Feyerabend. Atoms and Consciousness', in
     Common Knowledge Vol. 1, No. 1 1992: 28-32)"

Goals of scientific method

Because science has no experimental access to some things, there is no
'science of them'. Despite some popular impressions, it is not the goal of
science to answer all questions, nor even to 'explain' every phenomenon.
Some things are not now experimentally accessible. And science does not
produce truth; it merely improves the currently best hypothesis about some
aspect of reality. It cannot be a source of value judgements, though it can
certainly speak to matters of ethics and public policy by pointing to the
likely consequences of actions. However, science can't tell us which of
those consequences to desire or which is 'best'. What one projects from the
currently most reasonable scientific hypothesis onto other realms of
interest is not a scientific issue, and the scientific method offers no
assistance for those who wish to do so. Scientific justification for many
things is, nevertheless, often claimed.

Scientific Method and Public Policy Questions

In matters of public policy, the quality of 'scientific support' claimed for
a position is generally inversely related to that position's benefit to the
claimer. In short, if 'junk science' will help support a position that will
benefit me, only considerable ethical uprightness will prevent me from using
it. Such ethical standards are regrettably less common than we would all
hope among scientists as well as everyone else. Since the audience (i.e.,
everyone for some such debates) is rarely in a position to independently
evaluate the scientific support claimed by anyone on any side of the issue,
much 'junk science' has achieved prominence. Without mastering the
underlying science, about the only thing the non-scientist can do is attempt
to filter out economic and social interests, taking seriously only those who
don't seem to have a stake in having one or another position adopted as a
proxy for evaluating the quality of the science.

For instance, a chemical company caught dumping something in a local stream
claims it has scientific support for the harmlessness of the dumping and
therefore nothing should be done, certainly not at its expense, about the
dumping. The local law provides that those who dump dangerous stuff should
clean it up. Local environmentalists claim to have scientific support for
the danger and that therefore the company should be compelled to clean up
the contamination. What should local government do? How should the citizenry
judge the government's performance? A first evaluation is probably to look
to 'the science'. But, whose analysis is correct? Perhaps neither, but as a
first attempt to decide between the two positions, the company's financial
interest indicates that its scientific support need not be believed out of
hand. It has a higher burden of 'disbelief' because of that interest. In
such cases, governments often call for an independent scientific evaluation
and announce they will take action based on that report. At which point, the
dispute will change into an attempt to find 'independent' scientists who are
believed to be likely to support one side or the other.

These disputes are often wholly unscientific since they are essentially
economic or social, not scientific.

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