Scientific method
"The scientific method" usually refers to a series of processes that are considered characteristic of scientific investigation and the acquisition of new knowledge about the world.
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2 The scientific method in theory 3 The scientific method in practice 4 See also 5 External links |
Introduction
The first enunciation of a scientific method was by Roger Bacon in the thirteenth century, who described a repeating cycle of observation, hypothesis, experimentation and the need for independent verification. It spurns the use of unfounded speculation and analogical arguments.
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.
In fact, many see the course of scientific progress as inseparable from the politics and culture of science, and for them scientific method at least partly encompasses these influences. Scholars agree that scientific progress cannot be explained or prescribed as a single, formularizable process.
The question of how science operates is important beyond the community of scholars. 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." Science represents a standard of proficiency and reliability, and this is due at least in part to the way scientists work.
The idealized description of how scientists work is traditionally described as follows:
The scientific method in theory
Few people believe that there is any one method that all scientists follow like an algorithm. However, many people believe that the idealized scientific method captures the essence of how science operates. The elements of this method are described in more detail below.
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. The most important aspect of an explanation (ie, a 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.
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 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 those of the 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.
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.
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. 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.
Most philosophers of science are agreed that 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. 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.
History is replete with examples of accurate theories ignored by peers, and inaccurate ones propagated unduly, due to social factors. An example is the development of astronomical 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 accommodated by modifications of the model. Nicolaus Copernicus's model differed by placing the sun at the center of planetary 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.
Observation
Hypothesis
Prediction
Verification
Evaluation
The scientific method in practice
See also
External links
