Scientific method

===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.
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