Scientific method: Difference between revisions

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[[File:The Scientific Method.svg|thumb|upright=1.2|The scientific method is often represented as an [[#Elements of the scientific method|ongoing process]]. This diagram represents one variant, and [[commons:Category:Scientific method|there are many others]].]]

{{Science|expanded=Overview}}

The '''scientific method''' is an [[Empirical evidence|empirical]] method for acquiring [[knowledge]] that has characterized the development of [[science]] since at least the 17th century (with notable practitioners in previous centuries; see the article [[history of scientific method]] for additional detail.) It involves careful [[observation]], applying rigorous [[skepticism]] about what is observed, given that [[Philosophy of science#Observation inseparable from theory|cognitive assumptions]] can distort how one interprets the [[Perception#Process and terminology|observation]]. It involves formulating [[Hypothesis|hypotheses]], via [[Inductive reasoning|induction]], based on such observations; the [[testability]] of hypotheses, [[experiment]]al and the measurement-based statistical testing of [[Deductive reasoning|deductions]] drawn from the hypotheses; and refinement (or elimination) of the hypotheses based on the experimental findings. These are ''principles'' of the scientific method, as distinguished from a definitive series of steps applicable to all scientific enterprises.<ref>{{Cite book|title=Philosophiæ Naturalis Principia Mathematica|last=Newton|first=Issac|series=The Principia: Mathematical Principles of Natural Philosophy |publisher=University of California Press|others=Includes "A Guide to Newton's Principia" by I. Bernard Cohen, pp. 1–370. (The ''Principia'' itself is on pp. 371–946)|isbn=978-0-520-08817-7|location=Berkeley, CA|date=1999|at=791–796 ("Rules of Reasoning in Philosophy"); ''see also'' [[Philosophiæ Naturalis Principia Mathematica#Rules of Reason]]|translator-last=Cohen|translator-first=I. Bernard|trans-title=Mathematical Principles of Natural Philosophy|orig-year=1726 (3rd ed.)|translator-last2=Whitman|translator-first2=Anne|translator-last3=Budenz|translator-first3=Julia|title-link=Philosophiæ Naturalis Principia Mathematica}}</ref><ref>{{Citation|title=Oxford Dictionaries: British and World English|date=2016|chapter-url=http://www.oxforddictionaries.com/definition/english/scientific-method|chapter=scientific method|access-date=28 May 2016|archive-date=2016-06-20 |archive-url=https://web.archive.org/web/20160620062539/http://www.oxforddictionaries.com/definition/english/scientific-method|url-status=dead}}</ref><ref>{{Cite book|url=http://www.oed.com/view/Entry/383323|title=Oxford English Dictionary|via=OED Online|publisher=Oxford University Press|year=2014|edition=3rd|location=Oxford|url-access=subscription|access-date=2018-05-31 |archive-date=2023-11-29 |archive-url=https://web.archive.org/web/20231129112639/https://www.oed.com/dictionary/scientific-method_n|url-status=live}}</ref>

 

 

The purpose of an experiment is to determine whether [[#Characterizations|observation]]s{{efn-ua|name= aQuestion}}{{efn|name= fallingBodies}}{{efn|name= alhacenCharacterizes| ''[[Book of Optics]]'' (''circa'' 1027) After anatomical investigation of the human eye, and an exhaustive study of human visual perception, Alhacen characterizes the first postulate of [[Euclid's Optics]] as 'superfluous and useless'

==History==

{{Main|History of scientific method}}

 

The term "scientific method" emerged in the 19th century, when a significant institutional development of science was taking place and terminologies establishing clear [[Demarcation problem|boundaries]] between science and non-science, such as "scientist" and "pseudoscience", appeared.<ref name="Thurs" /> Throughout the 1830s and 1850s, at which time Baconianism was popular, naturalists like William Whewell, John Herschel, John Stuart Mill engaged in debates over "induction" and "facts" and were focused on how to generate knowledge.<ref name="Thurs" /> In the late 19th and early 20th centuries, a debate over [[Philosophical realism|realism]] vs. [[antirealism]] was conducted as powerful scientific theories extended beyond the realm of the observable.<ref name="auto">{{cite book |last=Achinstein |first= Peter |chapter=General Introduction |pages=1–5 |title=Science Rules: A Historical Introduction to Scientific Methods |publisher=Johns Hopkins University Press |date=2004 |isbn=978-0-8018-7943-2}}</ref>

{{efn-ua|name= introspection| [[instrumentalism|Never fail to recognize an idea]]... .— C. S. Peirce<ref name= How/>}}{{efn-ua|name= vacuum| Twenty-three hundred years ago, Aristotle proposed that a [[vacuum]] did not exist in nature; thirteen hundred years later, [[#alhazen|Alhazen disproved Aristotle's hypothesis]], using experiments on [[refraction]],<ref name=treatiseOnLight2>Alhacen (c.1035) ''Treatise on Light'' (رسالة في الضوء) as cited in [[Shmuel Sambursky]], ed. (1975) [https://archive.org/details/physicalthoughtf0000unse/page/136/mode/2up Physical thought from the Presocratics to the quantum physicists : an anthology], p.137</ref> thus deducing the existence of [[outer space]].<ref name= alhacenOnRefraction4.28 />}}

 

 

Different early expressions of empiricism and the scientific method can be found throughout history, for instance with the ancient [[Stoics]], [[Epicurus]],<ref name=Asmis>Elizabeth Asmis (1985) ''Epicurus' Scientific Method''. Cornell University Press</ref> [[Alhazen]],{{efn-ua|1=[[Alhazen]] argued the importance of forming questions and subsequently testing them: "How does light travel through transparent bodies? Light travels through transparent bodies in straight lines only... We have explained this exhaustively in our ''[[Book of Optics]]''.{{efn|name= straightLinesOnly }} But let us now mention something to prove this convincingly: the fact that light travels in straight lines is clearly observed in the lights which enter into dark rooms through holes.... [T]he entering light will be clearly observable in the dust which fills the air.<ref name=treatiseOnLight>Alhazen, ''Treatise on Light'' ({{lang|ar|رسالة في الضوء}}), translated into English from German by M. Schwarz, from [http://menadoc.bibliothek.uni-halle.de/dmg/periodical/pageview/30949 "Abhandlung über das Licht"] {{Webarchive|url=https://web.archive.org/web/20191230190424/http://menadoc.bibliothek.uni-halle.de/dmg/periodical/pageview/30949 |date=2019-12-30 }}, J. Baarmann (editor and translator from Arabic to German, 1882) ''[[Zeitschrift der Deutschen Morgenländischen Gesellschaft]]'' Vol '''36''' as quoted in {{harvnb|Sambursky|1975|p=136}}.</ref>

A sea voyage from America to Europe afforded [[C. S. Peirce]] the distance to clarify [[#coord3kinds|his ideas]],{{efn-ua| Distancing oneself from the problem is one technique for solving problems<ref name= How/>}} gradually resulting in the [[hypothetico-deductive model]].{{sfn|Godfrey-Smith|2003|p=236}} Formulated in the 20th century, the model has undergone significant revision since first proposed (for a more formal discussion, see {{slink||Elements of the scientific method}}).

 

 

 

* Characterizations (observations, definitions, and measurements of the subject of inquiry)

* Hypotheses (theoretical, hypothetical explanations of observations and measurements of the subject)

* Predictions (inductive and deductive reasoning from the hypothesis or theory)

* Experiments (tests of all of the above)

Each element of the scientific method is subject to [[peer review]] for possible mistakes. These activities do not describe all that scientists do but [[#Beliefs and biases|apply mostly to experimental sciences]] (e.g., physics, chemistry, biology, and psychology). The elements above are often taught in [[education|the educational system]] as "the scientific method".{{efn-ua|name= aQuestion| In the [[Inquiry-based learning|inquiry-based education]] paradigm, the stage of "characterization, observation, definition, ..." is more briefly summed up under the rubric of a Question. The question at some stage might be as basic as the [[5Ws]], or ''is this answer true?'', or ''who else might know this?'', or ''can I ask them?'', and so forth. The questions of the inquirer spiral until the goal is reached.}}

 

The scientific method is not a single recipe: it requires intelligence, imagination, and creativity.<ref>{{harvnb|Einstein|Infeld|1938|p=92}}: "To raise new questions, new possibilities, to regard old problems from a new angle, requires creative imagination and marks real advance in science."</ref> In this sense, it is not a mindless set of standards and procedures to follow, but is rather an [[#Evaluation and improvement|ongoing cycle]], constantly developing more useful, accurate, and comprehensive models and methods. For example, when Einstein developed the Special and General Theories of Relativity, he did not in any way refute or discount Newton's ''Principia''. On the contrary, if the astronomically massive, the feather-light, and the extremely fast are removed from Einstein's theories – all phenomena Newton could not have observed – Newton's equations are what remain. Einstein's theories are expansions and refinements of Newton's theories and, thus, increase confidence in Newton's work.

 

 

# Define a question

 

While this schema outlines a typical hypothesis/testing method,{{sfn|Gauch|2003|loc=esp. chapters 5–8}} many philosophers, historians, and sociologists of science, including [[Paul Feyerabend]],{{efn|name= descartes| "no opinion, however absurd and incredible, can be imagined, which has not been maintained by some of the philosophers". —Descartes<ref name= discourseOnMethod >[[René Descartes]] (1637) [https://en.wikisource.org/wiki/Discourse_on_the_Method/Part_2 Discourse on the Method/Part 2] {{Webarchive|url=https://web.archive.org/web/20210901150801/https://en.wikisource.org/wiki/Discourse_on_the_Method/Part_2 |date=2021-09-01 }} Part II</ref> }} claim that such descriptions of scientific method have little relation to the ways that science is actually practiced.

 

===Characterizations===

 

The systematic, careful collection of measurements or counts of relevant quantities is often the critical difference between [[Pseudoscience|pseudo-sciences]], such as alchemy, and science, such as chemistry or biology. Scientific measurements are usually tabulated, graphed, or mapped, and statistical manipulations, such as [[correlation]] and [[regression analysis|regression]], performed on them. The measurements might be made in a controlled setting, such as a laboratory, or made on more or less inaccessible or unmanipulatable objects such as stars or human populations. The measurements often require [[#Instrumentation|specialized]] [[scientific instrument]]s such as [[thermometer]]s, [[Spectrometer|spectroscopes]], [[particle accelerator]]s, or [[voltmeter]]s, and the progress of a scientific field is usually intimately tied to their invention and improvement.

 

{{Blockquote|text=I am not accustomed to saying anything with certainty after only one or two observations.|author=[[Andreas Vesalius]]|source=(1546)<ref>

 

====Uncertainty====

 

====Definition====

The scientific definition of a term sometimes differs substantially from its [[natural language]] usage. For example, [[mass]] and [[weight]] overlap in meaning in common discourse, but have distinct meanings in [[mechanics]]. Scientific quantities are often characterized by their [[units of measurement|units of measure]] which can later be described in terms of conventional physical units when communicating the work.

 

New theories are sometimes developed after realizing certain terms have not previously been sufficiently clearly defined. For example, [[Albert Einstein]]'s first paper on [[Special relativity|relativity]] begins by defining [[Relativity of simultaneity|simultaneity]] and the means for determining [[length]]. These ideas were skipped over by [[Isaac Newton]] with, "I do not define [[time in physics#Galileo: the flow of time|time]], space, place and [[motion (physics)|motion]], as being well known to all." Einstein's paper then demonstrates that they (viz., absolute time and length independent of motion) were approximations. [[Francis Crick]] cautions us that when characterizing a subject, however, it can be premature to define something when it remains ill-understood.<ref>Crick, Francis (1994), ''The Astonishing Hypothesis'' {{ISBN|0-684-19431-7}} p. 20

</ref> In Crick's study of [[consciousness]], he actually found it easier to study [[awareness]] in the [[visual system]], rather than to study [[free will]], for example. His cautionary example was the gene; the gene was much more poorly understood before Watson and Crick's pioneering discovery of the structure of DNA; it would have been counterproductive to spend much time on the definition of the gene, before them.

 

===Hypothesis development===

{{Main|Hypothesis formation}}

 

Normally hypotheses have the form of a [[mathematical model]]. Sometimes, but not always, they can also be formulated as [[existential quantification|existential statements]], stating that some particular instance of the phenomenon being studied has some characteristic and causal explanations, which have the general form of [[universal quantification|universal statements]], stating that every instance of the phenomenon has a particular characteristic.

 

 

[[William Glen (geologist and historian)|William Glen]] observes that{{sfn|Glen|1994|pp=37–38}}

In general scientists tend to look for theories that are "[[Elegance|elegant]]" or "[[beauty|beautiful]]". Scientists often use these terms to refer to a theory that is following the known facts but is nevertheless relatively simple and easy to handle. [[Occam's Razor]] serves as a rule of thumb for choosing the most desirable amongst a group of equally explanatory hypotheses.

 

 

===Predictions from the hypothesis===

 

 

It is essential that the outcome of testing such a prediction be currently unknown. Only in this case does a successful outcome increase the probability that the hypothesis is true. If the outcome is already known, it is called a consequence and should have already been considered while [[#Hypothesis development|formulating the hypothesis]].

If the predictions are not accessible by observation or experience, the hypothesis is not yet testable and so will remain to that extent unscientific in a strict sense. A new technology or theory might make the necessary experiments feasible. For example, while a hypothesis on the existence of other intelligent species may be convincing with scientifically based speculation, no known experiment can test this hypothesis. Therefore, science itself can have little to say about the possibility. In the future, a new technique may allow for an experimental test and the speculation would then become part of accepted science.

 

 

===Experiments===

 

 

 

|editor-last=Smith

|editor-first=A. Mark

|oclc= 47168716

}}</ref>{{efn|"And this [experiment using a [[camera obscura]]] can be tried anytime". Book I [6.86] p.379}}{{efn|''[[Book of Optics]]'' Book II [3.52] to [3.66] Summary p.444 for Alhazen's experiments on color; pp.343—394 for his physiological experiments on the eye}}{{efn|name= straightLinesOnly |''[[Book of Optics]]'' Book Seven, Chapter Two [2.1] p.220: — light travels through transparent bodies, such as air, water, glass, transparent stones, in straight lines. "Indeed, this is observable by means of experiment".<ref name= smith2010 >{{harvnb|Smith|2010|p=220}} Book Seven covers refraction.</ref> }}

 

===Evaluation and improvement===

 

 

{{anchor|otherScientists}}Other scientists may start their own research and [[#Other components|enter the process]] at any stage. They might adopt the characterization and formulate their own hypothesis, or they might adopt the hypothesis and deduce their own predictions. Often the experiment is not done by the person who made the prediction, and the characterization is based on experiments done by someone else. Published results of experiments can also serve as a hypothesis predicting their own reproducibility.

 

===Confirmation<!--Linked from [[Confirmation (disambiguation)]]-->===

Science is a social enterprise, and scientific work tends to be accepted by the scientific community when it has been confirmed. Crucially, experimental and theoretical results must be reproduced by others within the scientific community. Researchers have given their lives for this vision; [[Georg Wilhelm Richmann]] was killed by [[ball lightning]] (1753) when attempting to replicate the 1752 kite-flying experiment of [[Benjamin Franklin]].<ref>{{cite journal |last=Krider |first=E. Philip |date=Jan 2006 |title=Benjamin Franklin and lightning rods |journal=Physics Today |volume=59 |issue=1 |page=42 |doi=10.1063/1.2180176 |bibcode=2006PhT....59a..42K |s2cid=110623159 |quote=On 6 August 1753, the Swedish scientist Georg Wilhelm Richmann was electrocuted in St. Petersburg ...|doi-access=free }}</ref>

 

 

==Scientific inquiry==

 

Most experimental results do not produce large changes in human understanding; improvements in theoretical scientific understanding typically result from a gradual process of development over time, sometimes across different domains of science.<ref>Stanovich, Keith E. (2007). ''How to Think Straight About Psychology''. Boston: Pearson Education. p. 123</ref> Scientific models vary in the extent to which they have been experimentally tested and for how long, and in their acceptance in the scientific community. In general, explanations become accepted over time as evidence accumulates on a given topic, and the explanation in question proves more powerful than its alternatives at explaining the evidence. Often subsequent researchers re-formulate the explanations over time, or combined explanations to produce new explanations.

| date = 2010-09-11

}}

 

===Properties of scientific inquiry===

 

 

Theories can also become subsumed by other theories. For example, Newton's laws explained thousands of years of scientific observations of the planets [[#Another example: precession of Mercury|almost perfectly]]. However, these laws were then determined to be special cases of a more general theory ([[Theory of relativity|relativity]]), which explained both the (previously unexplained) exceptions to Newton's laws and predicted and explained other observations such as the deflection of [[light]] by [[gravity]]. Thus, in certain cases independent, unconnected, scientific observations can be connected, unified by principles of increasing explanatory power.{{sfn|Brody|1993 |pp=44–45}}{{sfn|Goldhaber|Nieto|2010|page=942}}

 

==Models of scientific inquiry==

{{cite book |author=[[Aristotle]] |chapter=[[Prior Analytics]] |translator=Hugh Tredennick |pages=181–531 |title=Aristotle, Volume&nbsp;1 |series=[[Loeb Classical Library]] |publisher=William Heinemann |place=London |year=1938}}

</ref> who distinguished the forms of approximate and exact reasoning, set out the threefold scheme of [[abductive reasoning|abductive]], [[deductive reasoning|deductive]], and [[inductive reasoning|inductive]] [[inference]], and also treated the compound forms such as reasoning by [[analogy]].

 

 

 

==Communication and community==

Frequently the scientific method is employed not only by a single person but also by several people cooperating directly or indirectly. Such cooperation can be regarded as an important element of a [[scientific community]]. Various standards of scientific methodology are used within such an environment.

 

Scientific journals use a process of ''[[peer review]]'', in which scientists' manuscripts are submitted by editors of scientific journals to (usually one to three, and usually anonymous) fellow scientists familiar with the field for evaluation. In certain journals, the journal itself selects the referees; while in others (especially journals that are extremely specialized), the manuscript author might recommend referees. The referees may or may not recommend publication, or they might recommend publication with suggested modifications, or sometimes, publication in another journal. This standard is practiced to various degrees by different journals and can have the effect of keeping the literature free of obvious errors and generally improve the quality of the material, especially in the journals that use the standard most rigorously. The peer-review process can have limitations when considering research outside the conventional scientific paradigm: problems of "[[groupthink]]" can interfere with open and fair deliberation of some new research.<ref>Brown, C. (2005) Overcoming Barriers to Use of Promising Research Among Elite Middle East Policy Groups, Journal of Social Behaviour and Personality, Select Press.</ref>

 

Researchers sometimes practice [[scientific data archiving]], such as in compliance with the policies of government funding agencies and scientific journals. In these cases, detailed records of their experimental procedures, raw data, statistical analyses, and source code can be preserved to provide evidence of the methodology and practice of the procedure and assist in any potential future attempts to [[Reproducibility|reproduce the result]]. These procedural records may also assist in the conception of new experiments to test the hypothesis, and may prove useful to engineers who might examine the potential practical applications of a discovery.

 

When additional information is needed before a study can be reproduced, the author of the study might be asked to provide it. They might provide it, or if the author refuses to [[data sharing|share data]], appeals can be made to the journal editors who published the study or to the institution which funded the research.

 

Since a scientist cannot record ''everything'' that took place in an experiment, facts selected for their apparent relevance are reported. This may lead, unavoidably, to problems later if some supposedly irrelevant feature is questioned. For example, [[Heinrich Hertz]] did not report the size of the room used to test Maxwell's equations, which later turned out to account for a small deviation in the results. The problem is that parts of the theory itself need to be assumed to select and report the experimental conditions. The observations are hence sometimes described as being 'theory-laden'.

 

}}</ref> He opens Chapter 1 with a discussion of the [[Golgi apparatus|Golgi bodies]] and their initial rejection as an artefact of staining technique, and a discussion of [[Tycho Brahe|Brahe]] and [[Johannes Kepler|Kepler]] observing the dawn and seeing a "different" sunrise despite the same physiological phenomenon.{{efn|name= Kepler1604 }}{{efn|Brahe and Kepler are two different observers, [[intersubjectivity]] validates Hanson.}} Kuhn<ref>{{cite book |last=Kuhn |first=Thomas S. |title=The Structure of Scientific Revolutions |publisher=University of Chicago Press |location=Chicago, IL |year=2009 |isbn=978-1-4432-5544-8 |page=113 |title-link=The Structure of Scientific Revolutions}}<!--ISBN matches 2009 publication, not the 1962.-->

</ref> and Feyerabend<ref>Feyerabend, Paul K (1960) "Patterns of Discovery" The Philosophical Review (1960) vol. 69 (2) pp. 247–252</ref> acknowledge the pioneering significance of Hanson's work.

 

===Post-modernism and science wars===

 

=== Relationship with statistics ===

 

 

===Role of chance in discovery===

 

==See also==

* {{Annotated link|Empirical limits in science}}

* {{Annotated link|Evidence-based practices}}

* {{Annotated link|Methodology}}

* {{Annotated link|Metascience}}

* {{Annotated link|Quantitative research}}

* {{Annotated link|Scientific law}}

* {{Annotated link|Testability}}

<!--* {{Annotated link|Sociology of scientific knowledge}}-->

* {{Annotated link|Timeline of the history of scientific method}}