Editing Scientific method (section)

==Elements of inquiry<span class="anchor" id="Elements of the scientific method"></span>==
{{anchor|Context}}
=== Overview ===

[[File:The Scientific Method.svg|thumb|upright=1|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]].]]

The scientific method is the process by which [[science]] is carried out.<ref name="allTheSciences">{{harvp|Gauch|2003|p=xv}}: "The thesis of this book, as outlined in Chapter One, is that there are general principles applicable to all the sciences."</ref> As in other areas of inquiry, science (through the scientific method) can build on previous knowledge, and unify understanding of its studied topics over time.{{efn|name=unification|1= The topics of study, as expressed in the vocabulary of its scientists, are approached by a "single unified method".<ref name= cowles />{{rp|pp.8,13,33–35,60}} The topics are [[Unification (computer science)|unified]] by its predicates, in a system of expressions. The unification process was formalized by [[Jacques Herbrand]] in 1930.<ref name= herbrand >Maribel Fernández [https://nms.kcl.ac.uk/maribel.fernandez/papers/slides-TCS-SOUP.pdf (Dec 2007) Unification Algorithms]</ref>}} Historically, the development of the scientific method was critical to the [[Scientific Revolution]].<ref name="lindberg2007">{{harvp|Lindberg|2007|pp=2–3}}: "There is a danger that must be avoided. ... If we wish to do justice to the historical enterprise, we must take the past for what it was. And that means we must resist the temptation to scour the past for examples or precursors of modern science. ...My concern will be with the beginnings of scientific ''theories'', the methods by which they were formulated, and the uses to which they were put; ... "</ref>

The overall process involves making conjectures ([[Hypothesis|hypotheses]]), predicting their logical consequences, then carrying out experiments based on those predictions to determine whether the original conjecture was correct.<ref name="NA" /> However, there are difficulties in a formulaic statement of method. Though the scientific method is often presented as a fixed sequence of steps, these actions are more accurately general principles.{{sfnp|Gauch|2003|p=3}} Not all steps take place in every scientific inquiry (nor to the same degree), and they are not always done in the same order.

==== Factors of scientific inquiry ====
There are different ways of outlining the basic method used for scientific inquiry. The [[scientific community]] and [[philosophers of science]] generally agree on the following classification of method components. These methodological elements and organization of procedures tend to be more characteristic of [[experimental science]]s than [[social science]]s. Nonetheless, the cycle of formulating hypotheses, testing and analyzing the results, and formulating new hypotheses, will resemble the cycle described below.{{anchor|epistemicCycle|Process}}The scientific method is an iterative, cyclical process through which information is continually revised.<ref>{{cite book |last1=Godfrey-Smith |first1=Peter |url=https://books.google.com/books?id=k23egtSWrb8C |title=Theory and Reality: An Introduction to the Philosophy of Science |date=2009 |publisher=University of Chicago Press |isbn=978-0-226-30062-7 |location=Chicago |author-link=Peter Godfrey-Smith |access-date=2020-05-09 |archive-url=https://web.archive.org/web/20231129112726/https://books.google.com/books?id=k23egtSWrb8C |archive-date=2023-11-29 |url-status=live}}</ref><ref name="Brody-1993">{{harvp|Brody|1993|p=10}} calls this an ''[[#epistemicCycle|epistemic cycle]]''; these cycles can occur at high levels of abstraction.</ref> It is generally recognized to develop advances in knowledge through the following elements, in varying combinations or contributions:<ref name="Fixation">{{cite wikisource|title=The Fixation of Belief|first=Charles Sanders|last=Peirce|year=1877|wslink=The Fixation of Belief|volume=12|pages=1–15|journal=Popular Science Monthly}}.</ref><ref name="Vital">Peirce, Charles S., ''Collected Papers'' v. 5, in paragraph 582, from 1898: "...&nbsp;[rational] inquiry of every type, fully carried out, has the vital power of self-correction and of growth. This is a property so deeply saturating its inmost nature that it may truly be said that there is but one thing needful for learning the truth, and that is a hearty and active desire to learn what is true."</ref><!--ref>{{cite book|last1=Kuhn |first1=Thomas S.|title=The Structure of Scientific Revolutions 50th Anniversary Edition|date=2012 |publisher=University of Chicago Press|location=Chicago|isbn=978-0-226-45811-3 |url=https://books.google.com/books?id=3eP5Y_OOuzwC|access-date=29 January 2018}}{{pn|date=August 2021}}</ref><ref>{{cite book|last1=Galison |first1=Peter|title=How Experiments End|date=1987|publisher=University of Chicago Press|location=Chicago|isbn=978-0-226-27915-2|url=https://books.google.com/books?id=DN-9m2jSo8YC |access-date=29 January 2018}}</ref-->
* 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>{{harvp|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.

{{anchor|aGuideline}}An iterative,<ref name="Brody-1993" /> pragmatic<ref name="truthSought4sake" /> scheme of the four points above is sometimes offered as a guideline for proceeding:<ref>{{cite journal |vauthors=Crawford S, Stucki L |year=1990 |title=Peer review and the changing research record |journal=Journal of the American Society for Information Science |volume=41 |issue=3 |pages=223–228 |doi=10.1002/(SICI)1097-4571(199004)41:3<223::AID-ASI14>3.0.CO;2-3}}</ref>

# Define a question
# Gather information and resources (observe)
# Form an explanatory hypothesis
# Test the hypothesis by performing an experiment and collecting data in a [[Reproducibility|reproducible]] manner
# Analyze the data
# Interpret the data and draw conclusions that serve as a starting point for a new hypothesis
# Publish results
# Retest (frequently done by other scientists)

The iterative cycle inherent in this step-by-step method goes from point 3 to 6 and back to 3 again.

While this schema outlines a typical hypothesis/testing method,{{sfnp|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.

=== <span class="anchor" id="DNA-characterizations"></span> Characterizations===

The basic elements of the scientific method are illustrated by the following example (which occurred from 1944 to 1953) from the discovery of the structure of DNA (marked with [[File:DNA icon.svg|frameless|22x22px|link=|alt=DNA label]] and indented).

<blockquote>[[File:DNA icon.svg|frameless|22x22px|link=|alt=DNA label]] In 1950, it was known that [[genetic inheritance]] had a mathematical description, starting with the studies of [[Gregor Mendel]], and that DNA contained genetic information (Oswald Avery's ''transforming principle'').{{sfnp|McCarty|1985|page=252}} But the mechanism of storing genetic information (i.e., genes) in DNA was unclear. Researchers in [[William Lawrence Bragg|Bragg's]] laboratory at [[University of Cambridge|Cambridge University]] made [[X-ray]] [[diffraction]] pictures of various [[molecule]]s, starting with [[crystal]]s of [[salt]], and proceeding to more complicated substances. Using clues painstakingly assembled over decades, beginning with its chemical composition, it was determined that it should be possible to characterize the physical structure of DNA, and the X-ray images would be the vehicle.{{sfnp|McElheny|2004|p=34}}</blockquote>

The scientific method depends upon increasingly sophisticated characterizations of the subjects of investigation. (The ''subjects'' can also be called [[:Category:Lists of unsolved problems|''unsolved problems'']] or the ''unknowns''.){{efn-ua|name= aQuestion}} For example, [[Benjamin Franklin]] conjectured, correctly, that [[St. Elmo's fire]] was [[electrical]] in [[nature]], but it has taken a long series of experiments and theoretical changes to establish this. While seeking the pertinent properties of the subjects, careful thought may also [[logical consequence|entail]] some definitions and [[observations]]; these observations often demand careful [[measurements]] and/or counting can take the form of expansive [[empirical research]].

A [[Research question|scientific question]] can refer to the explanation of a specific [[observation]],{{efn-ua|name= aQuestion}} as in "Why is the sky blue?" but can also be open-ended, as in "How can I [[Drug design|design a drug]] to cure this particular disease?" This stage frequently involves finding and evaluating evidence from previous experiments, personal scientific observations or assertions, as well as the work of other scientists. If the answer is already known, a different question that builds on the evidence can be posed. When applying the scientific method to research, determining a good question can be very difficult and it will affect the outcome of the investigation.<ref>{{cite book |url=https://books.google.com/books?id=C7pZftbI0ZMC |title=Translational and Experimental Clinical Research |publisher=Lippincott Williams & Wilkins |year=2005 |isbn=9780781755658 |editor-last1=Schuster |editor-first1=Daniel P. |chapter=Ch. 1 |access-date=2021-11-27 |editor-last2=Powers |editor-first2=William J. |archive-url=https://web.archive.org/web/20231129112636/https://books.google.com/books?id=C7pZftbI0ZMC |archive-date=2023-11-29 |url-status=live}} This chapter also discusses the different types of research questions and how they are produced.</ref>

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 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]] (1546)<ref>Andreas Vesalius, ''Epistola, Rationem, Modumque Propinandi Radicis Chynae Decocti'' (1546), p. 141. Quoted and translated in C.D. O'Malley, ''Andreas Vesalius of Brussels'', (1964), p. 116. As quoted by {{harvp|Bynum|Porter|2005|p=597}}: "Andreas Vesalius"</ref>}}

====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}}
<blockquote>{{Anchor|DNA-hypotheses}}[[File:DNA icon.svg|frameless|22x22px|link=|alt=DNA label]] [[Linus Pauling]] proposed that DNA might be a [[triple helix]].<ref>{{harvp|McElheny|2004|p=40}}: October 1951 — "That's what a helix should look like!" Crick exclaimed in delight (This is the Cochran-Crick-Vand-Stokes theory of the transform of a helix).</ref><ref>
{{harvp|Judson|1979|p=157}}. {{"'}}The structure that we propose is a three-chain structure, each chain being a helix' – Linus Pauling"</ref> This hypothesis was also considered by [[Francis Crick]] and [[James D. Watson]] but discarded. When Watson and Crick learned of Pauling's hypothesis, they understood from existing data that Pauling was wrong.<ref>
{{harvp|McElheny|2004|pp=49–50}}: January 28, 1953 — Watson read Pauling's pre-print, and realized that in Pauling's model, DNA's phosphate groups had to be un-ionized. But DNA is an acid, which contradicts Pauling's model.
</ref> and that Pauling would soon admit his difficulties with that structure.</blockquote>

{{Anchor|Hypothesis}}A [[hypothesis]] is a suggested explanation of a phenomenon, or alternately a reasoned proposal suggesting a possible correlation between or among a set of phenomena. 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.

Scientists are free to use whatever resources they have – their own creativity, ideas from other fields, [[inductive reasoning]], [[Bayesian inference]], and so on – to imagine possible explanations for a phenomenon under study. {{anchor|noLogicalBridge}}Albert Einstein once observed that "there is no logical bridge between phenomena and their theoretical principles."<ref>{{cite book |last1=Einstein |first1=Albert |title=The World as I See It |date=1949 |publisher=Philosophical Library |location=New York |pages=24–28}}</ref>{{efn|name= leapIsInvolved |"A leap is involved in all thinking" —John Dewey<ref>{{harvp|Dewey|1910|p=26}}</ref> }} [[Charles Sanders Peirce]], borrowing a page from [[Aristotle]] (''[[Prior Analytics]]'', [[Inquiry#Abduction|2.25]])<ref name="aristotleAbduction">[https://en.wikisource.org/wiki/Organon_(Owen)/Prior_Analytics/Book_2#Chapter_25 Aristotle (trans. 1853) ''Prior Analytics'' 2.25] {{Webarchive|url=https://web.archive.org/web/20210910034741/https://en.wikisource.org/wiki/Organon_(Owen)/Prior_Analytics/Book_2#Chapter_25 |date=2021-09-10  }} via Wikisource</ref> described the incipient stages of [[inquiry]], instigated by the "irritation of doubt" to venture a plausible guess, as ''[[abductive reasoning]]''.<ref name="How">{{cite wikisource|title=How to Make Our Ideas Clear|first=Charles Sanders|last=Peirce|year=1877|wslink=How to Make Our Ideas Clear|volume=12|pages=286–302|journal=Popular Science Monthly}}</ref>{{rp|II, p.290}} The history of science is filled with stories of scientists claiming 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 centerpiece of his discussion of methodology.

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

{{Blockquote|text=the success of a hypothesis, or its service to science, lies not simply in its perceived "truth", or power to displace, subsume or reduce a predecessor idea, but perhaps more in its ability to stimulate the research that will illuminate&nbsp;... bald suppositions and areas of vagueness.|author= William Glen|title= ''The Mass-Extinction Debates'' }}

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.

To minimize the [[confirmation bias]] that results from entertaining a single hypothesis, [[strong inference]] emphasizes the need for entertaining multiple alternative hypotheses,<ref name="platt">{{cite journal |last=Platt |first=John R. |author-link=John R. Platt |date=16 October 1964 |title=Strong Inference |journal=Science |volume=146 |issue=3642 |pages=347– |doi=10.1126/science.146.3642.347|pmid=17739513 |bibcode=1964Sci...146..347P }}</ref> and avoiding artifacts.<ref name= sn1987a>[[Leon Lederman]], for teaching [[physics first]], illustrates how to avoid confirmation bias: [[Ian Shelton]], in Chile, was initially skeptical that [[supernova 1987a]] was real, but possibly an artifact of instrumentation (null hypothesis), so he went outside and disproved his null hypothesis by observing SN 1987a with the naked eye. The [[Kamiokande]] experiment, in Japan, independently observed [[neutrino]]s from [[SN 1987a]] at the same time.</ref>

===Predictions from the hypothesis===
{{Further|Prediction#Science}}<blockquote>{{Anchor|DNA-predictions}}[[File:DNA icon.svg|frameless|22x22px|link=|alt=DNA label]] [[James D. Watson]], [[Francis Crick]], and others hypothesized that DNA had a helical structure. This implied that DNA's X-ray diffraction pattern would be 'x shaped'.<ref name="Crick pp. 137–138">{{harvp|Judson|1979|pp=137–138}}: "Watson did enough work on [[Tobacco mosaic virus]] to produce the diffraction pattern for a helix, per Crick's work on the transform of a helix."</ref><ref name="McElheny 2004 43">{{harvp|McElheny|2004|p=43}}: June 1952 — Watson had succeeded in getting X-ray pictures of TMV showing a diffraction pattern consistent with the transform of a helix.</ref> This prediction followed from the work of Cochran, Crick and Vand<ref name="HelixTransform">Cochran W, Crick FHC and Vand V. (1952) "The Structure of Synthetic Polypeptides. I. The Transform of Atoms on a Helix", ''[[Acta Crystallographica|Acta Crystallogr.]]'', '''5''', 581–586.</ref> (and independently by Stokes). The Cochran-Crick-Vand-Stokes theorem provided a mathematical explanation for the empirical observation that diffraction from helical structures produces x-shaped patterns.

In their first paper, Watson and Crick also noted that the [[double helix]] structure they proposed provided a simple mechanism for [[DNA replication]], writing, "It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material".<ref>{{harvp|McElheny|2004|p=68}}: ''Nature'' April 25, 1953.</ref></blockquote>{{Anchor|Prediction}}Any useful hypothesis will enable [[prediction]]s, by [[reasoning]] including [[deductive reasoning]].{{efn|1= From the hypothesis, deduce valid forms using [[Deductive reasoning#Modus ponens|modus ponens]], or using [[Deductive reasoning#Modus tollens|modus tollens]]. Avoid invalid forms such as [[affirming the consequent]].}} It might predict the outcome of an experiment in a laboratory setting or the observation of a phenomenon in nature. The prediction can also be statistical and deal only with probabilities.

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 [[testability|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.

For example, Einstein's theory of [[general relativity]] makes several specific predictions about the observable structure of [[spacetime]], such as that [[light]] bends in a [[gravitational field]], and that the amount of bending depends in a precise way on the strength of that gravitational field. [[Arthur Eddington]]'s [[Eddington experiment|observations made during a 1919 solar eclipse]] supported General Relativity rather than Newtonian [[gravitation]].<ref>In March 1917, the [[Royal Astronomical Society]] announced that on May 29, 1919, the occasion of a [[total eclipse]] of the sun would afford favorable conditions for testing Einstein's [[General theory of relativity]]. One expedition, to [[Sobral, Ceará]], [[Brazil]], and Eddington's expedition to the island of [[Principe]] yielded a set of photographs, which, when compared to photographs taken at [[Sobral, Ceará|Sobral]] and at [[Greenwich Observatory]] showed that the deviation of light was measured to be 1.69 [[arc-second]]s, as compared to Einstein's desk prediction of 1.75 [[arc-second]]s. – Antonina Vallentin (1954), ''Einstein'', as quoted by Samuel Rapport and Helen Wright (1965), ''Physics'', New York: Washington Square Press, pp. 294–295.</ref>

===Experiments===
{{Main|Experiment}}<blockquote>{{Anchor|DNA-experiments}}[[File:DNA icon.svg|frameless|22x22px|link=|alt=DNA label]] Watson and Crick showed an initial (and incorrect) proposal for the structure of DNA to a team from [[King's College London]] – [[Rosalind Franklin]], [[Maurice Wilkins]], and [[Raymond Gosling]]. Franklin immediately spotted the flaws which concerned the water content. Later Watson saw Franklin's [[photo 51]], a detailed X-ray diffraction image, which showed an X-shape<ref>{{cite web |title=The Secret of Photo 51 |url=https://www.pbs.org/wgbh/nova/photo51/ |url-status=live |archive-url=https://web.archive.org/web/20170831201252/http://www.pbs.org/wgbh/nova/photo51/ |archive-date=2017-08-31 |access-date=2017-09-11 |work=NOVA |publisher=PBS}}</ref><ref name=photo51Explained >[[Cynthia Wolberger]] [https://www.youtube.com/watch?v=2tMuMRY1oDo (2021) Photograph 51 explained]</ref> and was able to confirm the structure was helical.<ref name="TeaTime">{{harvp|McElheny|2004|p=52}}: Friday, January 30, 1953. Tea time — Franklin confronts Watson and his paper – "Of course it [Pauling's pre-print] is wrong. DNA is not a helix." However, Watson then visits Wilkins' office, sees [[photo 51]], and immediately recognizes the diffraction pattern of a helical structure. But additional questions remained, requiring additional iterations of their research. For example, the number of strands in the backbone of the helix (Crick suspected 2 strands, but cautioned Watson to examine that more critically), the location of the base pairs (inside the backbone or outside the backbone), etc. One key point was that they realized that the quickest way to reach a result was not to continue a mathematical analysis, but to build a physical model. Later that evening — Watson urges Wilkins to begin model-building immediately. But Wilkins agrees to do so only after Franklin's departure.</ref><ref name="Watson 1968 167">{{harvp|Watson|1968|p=167}}: "The instant I saw the picture my mouth fell open and my pulse began to race." Page 168 shows the X-shaped pattern of the B-form of [[DNA]], clearly indicating crucial details of its helical structure to Watson and Crick.</ref>{{efn|name= nextItemToSettle| The goal shifts: after observing the x-ray diffraction pattern of DNA,<ref name=TeaTime /><ref name=photo51Explained /> and as time was of the essence,<ref name=econ/> Watson and Crick realize that fastest way to discover DNA's structure was not by mathematical analysis,<ref name= reasonsFirstRule /> but by [[#DNA-iterations|building physical models]].<ref name= SameShape />}}</blockquote>
{{anchor|suitableTest|Testing|Crucial experiment}}Once predictions are made, they can be sought by experiments. If the test results contradict the predictions, the hypotheses which entailed them are called into question and become less tenable. Sometimes the experiments are conducted incorrectly or are not very well designed when compared to a [[crucial experiment]]. If the experimental results confirm the predictions, then the hypotheses are considered more likely to be correct, but might still be wrong and continue to be subject to [[#Evaluation and improvement|further testing.]] The [[experimental control]] is a technique for dealing with observational error. This technique uses the contrast between multiple samples, or observations, or populations, under differing conditions, to see what varies or what remains the same. We vary the conditions for the acts of measurement, to help isolate what has changed. [[Mill's canons]] can then help us figure out what the important factor is.<ref>[[John Stuart Mill|Mill, John Stuart]], "A System of Logic", University Press of the Pacific, Honolulu, 2002, {{ISBN|1-4102-0252-6}}.</ref> [[Factor analysis]] is one technique for discovering the important factor in an effect.

Depending on the predictions, the experiments can have different shapes. It could be a classical experiment in a laboratory setting, a [[double-blind]] study or an archaeological [[excavation (archaeology)|excavation]]. Even taking a plane from [[New York City|New York]] to [[Paris]] is an experiment that tests the [[aerodynamics|aerodynamical]] hypotheses used for constructing the plane.

These institutions thereby reduce the research function to a cost/benefit,<ref name="conjugatePairs" /> which is expressed as money, and the time and attention of the researchers to be expended,<ref name="conjugatePairs" /> in exchange for a report to their constituents.<ref name="nsf">National Science Foundation (NSF)  (2021) [https://www.nsf.gov/oig/reports/ NSF Reports] {{Webarchive|url=https://web.archive.org/web/20210817165231/https://www.nsf.gov/oig/reports/|date=2021-08-17}} and [https://www.nsf.gov/news/ News] {{Webarchive|url=https://web.archive.org/web/20210820162008/https://www.nsf.gov/news/|date=2021-08-20}}</ref> Current large instruments, such as CERN's [[Large Hadron Collider]] (LHC),<ref name="lhc">{{Cite web |title=LHC long term schedule |url=https://lhc-commissioning.web.cern.ch/lhc-commissioning/schedule/LHC-long-term.htm |url-status=live |archive-url=https://web.archive.org/web/20200425105121/https://lhc-commissioning.web.cern.ch/lhc-commissioning/schedule/LHC-long-term.htm |archive-date=2020-04-25 |access-date=2021-08-22 |website=lhc-commissioning.web.cern.ch}} (2021)</ref> or [[LIGO]],<ref name="ligo">{{cite web |title=ligo.caltech.edu (1999) Laser Interferometer Gravitational-Wave Observatory |url=https://www.ligo.caltech.edu/ |url-status=live |archive-url=https://web.archive.org/web/20210901125538/https://www.ligo.caltech.edu/ |archive-date=2021-09-01 |access-date=2021-08-30}}</ref> or the [[National Ignition Facility]] (NIF),<ref name="nif">{{cite web |title=NIF (2021) What Is the National Ignition Facility? |url=https://lasers.llnl.gov/about/what-is-nif |url-status=live |archive-url=https://web.archive.org/web/20170731064919/https://lasers.llnl.gov/about/what-is-nif |archive-date=2017-07-31 |access-date=2021-08-22}}</ref> or the [[International Space Station]] (ISS),<ref name="iss">{{cite web |date=12 January 2015 |title=ISS (2021) International Space Station |url=https://www.nasa.gov/mission_pages/station/main/index.html |url-status=live |archive-url=https://web.archive.org/web/20050907073730/http://www.nasa.gov/mission_pages/station/main/index.html |archive-date=2005-09-07 |access-date=2021-08-22}}</ref> or the [[James Webb Space Telescope]] (JWST),<ref name="jwst">{{cite web |title=JWST (2021) WEBB Space Telescope |url=https://www.jwst.nasa.gov/ |url-status=live |archive-url=https://web.archive.org/web/20120104225155/http://www.jwst.nasa.gov/ |archive-date=2012-01-04 |access-date=2021-08-22}}</ref><ref name="jwstDeploymentSeq">James Webb Space Telescope (JWST) [https://www.youtube.com/watch?v=RzGLKQ7_KZQ (12 Nov 2021) James Webb Space Telescope Deployment Sequence (Nominal)] {{Webarchive|url=https://web.archive.org/web/20211223035530/https://www.youtube.com/watch?v=RzGLKQ7_KZQ|date=2021-12-23}} highlights the predictions from launch to day+29,</ref> entail expected costs of billions of dollars, and timeframes extending over decades. These kinds of institutions affect public policy, on a national or even international basis, and the researchers would require shared access to such machines and their [[#otherScientists|adjunct infrastructure]].{{efn-lg|name= feedTheMachinery| The machinery of the mind can only transform knowledge, but never originate it, unless it be fed with facts of observation. —[[C.S. Peirce]]<ref name= How/>}}<ref name="Crutchfield" >{{cite web|url=http://csc.ucdavis.edu/~chaos/chaos/talks/CSTheorySFIRetreat.pdf|title=James Crutchfield (2003) "Complex Systems Theory?"|access-date=2018-05-27 |archive-date=2021-04-18 |archive-url=https://web.archive.org/web/20210418204840/http://csc.ucdavis.edu/~chaos/chaos/talks/CSTheorySFIRetreat.pdf|url-status=live}}</ref>

{{anchor|ethicalPosition}}Scientists assume an attitude of openness and accountability on the part of those experimenting. Detailed record-keeping is essential, to aid in recording and reporting on the experimental results, and supports the effectiveness and integrity of the procedure. They will also assist in reproducing the experimental results, likely by others. Traces of this approach can be seen in the work of [[Hipparchus]] (190–120 BCE), when determining a value for the precession of the Earth, while [[Scientific control|controlled experiments]] can be seen in the works of [[Muhammad ibn Jābir al-Harrānī al-Battānī|al-Battani]] (853–929 CE)<ref>[[Muhammad ibn Jābir al-Harrānī al-Battānī|al-Battani]], ''De Motu Stellarum'' [[Latin translations of the 12th century|translation from Arabic to Latin in 1116]], as cited by E. S. Kennedy, ''A Survey of Islamic Astronomical Tables,'' (Transactions of the American Philosophical Society, New Series, 46, 2), Philadelphia, 1956, pp. 10–11, 32–34.</ref> and [[#alhazen|Alhazen]] (965–1039 CE).{{sfnp|Smith|2001b}}{{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{{sfnp|Smith|2001b}} }}{{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 >{{harvp|Smith|2010|p=220}} Book Seven covers refraction.</ref> }}

===Communication and iteration===

{{See also|Scientific literature|Scholarly communication}}

<blockquote>
{{Anchor|DNA-iterations}}[[File:DNA icon.svg|frameless|22x22px|link=|alt=DNA label]] Watson and Crick then produced their model, using this information along with the previously known information about DNA's composition, especially Chargaff's rules of base pairing.<ref name="SameShape">{{harvp|McElheny|2004|pp=57–59}}: Saturday, February 28, 1953 — Watson found the base-pairing mechanism which explained [[Chargaff's rules]] using his cardboard models.</ref> After considerable fruitless experimentation, being discouraged by their superior from continuing, and numerous false starts,<ref>{{harvp|McElheny|2004|p=53}}: The weekend (January 31 – February 1) — After seeing photo 51, Watson informed Bragg of the X-ray diffraction image of DNA in B form. Bragg permitted them to restart their research on DNA (that is, model building).</ref><ref>{{harvp|McElheny|2004|p=54}}: Sunday, February 8, 1953 — Maurice Wilkes gave Watson and Crick permission to work on models, as Wilkes would not be building models until Franklin left DNA research.</ref><ref>{{harvp|McElheny|2004|p=56}}: [[Jerry Donohue]], on sabbatical from Pauling's lab and visiting Cambridge, advises Watson that the textbook form of the base pairs was incorrect for DNA base pairs; rather, the keto form of the base pairs should be used instead. This form allowed the bases' hydrogen bonds to pair 'unlike' with 'unlike', rather than to pair 'like' with 'like', as Watson was inclined to model, based on the textbook statements. On February 27, 1953, Watson was convinced enough to make cardboard models of the nucleotides in their keto form.</ref> Watson and Crick were able to infer the essential structure of [[DNA]] by concrete [[model (abstract)|modeling]] [[DNA#History|of the physical shapes]] of the [[nucleotide]]s which comprise it.<ref name="SameShape" /><ref>
{{harvp|Watson|1968|pp=194–197}}: "Suddenly I became aware that an [[adenine]]-[[thymine]] pair held together by two [[hydrogen bond]]s was identical in shape to a [[guanine]]-[[cytosine]] pair held together by at least two hydrogen bonds.&nbsp;..."</ref><ref>
{{harvp|McElheny|2004|p=57}}: Saturday, February 28, 1953 — Watson tried 'like with like' and admitted these base pairs didn't have hydrogen bonds that line up. But after trying 'unlike with unlike', and getting [[Jerry Donohue]]'s approval, the base pairs turned out to be identical in shape (as Watson stated above in his 1968 ''Double Helix'' memoir quoted above). Watson now felt confident enough to inform Crick. (Of course, 'unlike with unlike' increases the number of possible [[codon]]s, if this scheme were a [[genetic code]].)
</ref> They were guided by the bond lengths which had been deduced by [[Linus Pauling]] and by [[Rosalind Franklin]]'s X-ray diffraction images.
</blockquote>

{{Anchor|Analysis}}The scientific method is iterative. At any stage, it is possible to refine its [[accuracy and precision]], so that some consideration will lead the scientist to repeat an earlier part of the process. Failure to develop an interesting hypothesis may lead a scientist to re-define the subject under consideration. Failure of a hypothesis to produce interesting and testable predictions may lead to reconsideration of the hypothesis or of the definition of the subject. Failure of an experiment to produce interesting results may lead a scientist to reconsider the experimental method, the hypothesis, or the definition of the subject.

{{anchor|alhazen}}This manner of iteration can span decades and sometimes centuries. [[Academic publishing#Types of academic paper|Published papers]] can be built upon. For example: By 1027, [[Alhazen]], based on his measurements of the [[refraction]] of light, was able to deduce that [[outer space]] was less dense than [[air]], that is: "the body of the heavens is rarer than the body of air".<ref name="alhacenOnRefraction4.28">{{harvp|Smith|2010}} Book 7, [4.28] p.270</ref> In 1079 [[Ibn Mu'adh al-Jayyani|Ibn Mu'adh]]'s ''Treatise On Twilight'' was able to infer that Earth's atmosphere was 50 miles thick, based on [[atmospheric refraction]] of the sun's rays.{{efn|name= crepusculis|1= The Sun's rays are still visible at [[twilight]] in the morning and evening due to atmospheric refraction even when the depression angle of the sun is 18° below the horizon.<ref name= brGoldstein >Goldstein, Bernard R. (1977) [[Ibn Mu'adh al-Jayyani|Ibn Mu'adh]]'s "[https://www.jstor.org/stable/41133483 (1079) Treatise On Twilight and the Height of the Atmosphere] {{Webarchive|url=https://web.archive.org/web/20220921011840/https://www.jstor.org/stable/41133483 |date=2022-09-21  }}" ''[[Archive for History of Exact Sciences]]'' Vol. '''17''', No. 2 (21.VII.1977), pp. 97–118 (22 pages) JSTOR. (''Treatise On Twilight'' was printed by F Risner in ''Opticae Thesaurus'' (1572) as ''Liber de crepusculis'', but attributed to Alhazen rather than Ibn Mu'adh.)</ref> }}

This is why the scientific method is often represented as circular – new information leads to new characterisations, and the cycle of science continues. Measurements collected [[Research data archiving|can be archived]], passed onwards and used by others. {{anchor|otherScientists}}Other scientists may start their own research and [[#aGuideline|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)]]-->===
{{Main|Reproducibility}}
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>

{{anchor|Evaluation and improvement}}If an experiment cannot be [[Reproducibility|repeated]] to produce the same results, this implies that the original results might have been in error. As a result, it is common for a single experiment to be performed multiple times, especially when there are uncontrolled variables or other indications of [[Observational error|experimental error]]. For significant or surprising results, other scientists may also attempt to replicate the results for themselves, especially if those results would be important to their own work.<ref>{{cite web |title=Reconstruction of Galileo Galilei's experiment – the inclined plane |url=http://www.fyysika.ee/vorgustik/wp-content/uploads/2011/11/Reconstruction-of-Galileo-Galilei.pdf |url-status=live |archive-url=https://web.archive.org/web/20140429075745/http://www.fyysika.ee/vorgustik/wp-content/uploads/2011/11/Reconstruction-of-Galileo-Galilei.pdf |archive-date=2014-04-29 |access-date=2014-04-28}}</ref> Replication has become a contentious issue in social and biomedical science where treatments are administered to groups of individuals. Typically an ''experimental group'' gets the treatment, such as a drug, and the ''control group'' gets a placebo. [[John Ioannidis]] in 2005 pointed out that the method being used has led to many findings that cannot be replicated.<ref>{{cite journal |last=Ioannidis |first=John P. A. |date=August 2005 |title=Why most published research findings are false |journal=[[PLOS Medicine]] |volume=2 |issue=8 |pages=e124 |doi=10.1371/journal.pmed.0020124 |pmc=1182327 |pmid=16060722 |doi-access=free}}</ref>

The process of [[peer review]] involves the evaluation of the experiment by experts, who typically give their opinions anonymously. Some journals request that the experimenter provide lists of possible peer reviewers, especially if the field is highly specialized. Peer review does not certify the correctness of the results, only that, in the opinion of the reviewer, the experiments themselves were sound (based on the description supplied by the experimenter). If the work passes peer review, which occasionally may require new experiments requested by the reviewers, it will be published in a peer-reviewed [[Academic journal|scientific journal]]. The specific journal that publishes the results indicates the perceived quality of the work.{{efn|In ''Two New Sciences'', there are three 'reviewers': Simplicio, Sagredo, and Salviati, who serve as foil, antagonist, and protagonist. Galileo speaks for himself only briefly. But Einstein's 1905 papers were not peer-reviewed before their publication.}}

Scientists typically are careful in recording their data, a requirement promoted by [[Ludwik Fleck]] (1896–1961) and others.{{sfnp|Fleck|1979|pp=xxvii–xxviii}} Though not typically required, they might be requested to [[Data sharing|supply this data]] to other scientists who wish to replicate their original results (or parts of their original results), extending to the sharing of any experimental samples that may be difficult to obtain.<ref>"[http://grants.nih.gov/grants/policy/data_sharing/index.htm NIH Data Sharing Policy] {{Webarchive|url=https://web.archive.org/web/20120513171213/http://grants.nih.gov/grants/policy/data_sharing/index.htm|date=2012-05-13}}."</ref> To protect against bad science and fraudulent data, government research-granting agencies such as the [[National Science Foundation]], and science journals, including ''Nature'' and ''Science'', have a policy that researchers must archive their data and methods so that other researchers can test the data and methods and build on the research that has gone before. [[Scientific data archiving]] can be done at several national archives in the U.S. or the [[World Data Center]].