Dating
Literally, the dating is the attribution of a date. This term can thus apply to a last event, a Objet, a Document, a Fossile, a geological layer or a archaeological level. It indicates overall the step, Scientifique or not, which consists in determining the time interval separating the element time present.
One speaks about “absolute Datation” when the dating implemented leads to a quantified result expressed in Unité of time (years, seconds, etc). By opposition, the expression “relative Datation” indicates the step which consists in determining the chronological order of events or objects of the past, without knowing their real ages. A confusion is sometimes made between the two, when within the framework of a relative dating, the chronology extends until the present - thus, the “ages” of the periods defined by relative dating in Stratigraphie are often taken for money cash, although they have direction only like definite circumscribed time intervals by report/ratio with all the others.
Dating by the written sources
Before the middle of the 20th century, the written sources (texts, inscriptions, etc) constituted the principal elements of dating at the disposal of the Historien S to carry out the dating of the historical events, with the risks of inaccuracies and error that comprises.
Relative dating
See also: relative Dating
Before the development of the absolute methods of dating, the age of the prehistoric events (or historical events for which no written source was available) could be established only relatively: such event is older or more recent than such other.
The relative dating primarily bases on the basic principles of the stratigraphic method , developed since the 18th century, namely the Principe of continuity (the same layer has the same age on all its extent) and the Principe of superposition (a layer is more recent than that which it recovers). The Biochronologie, based on the study of the paleontological contents of the geological layers, was an important source of information to establish the relative age of certain grounds.
Absolute dating
See also: absolute Dating, radiometric Dating
The absolute dating is often restricted with the Radiochronologie, but there exist other qualifiable methods the absolute ones: the Dendrochronologie, the Archéomagnétisme… It is true however that the precision and the panel of durations covered by the isotopic methods are without equivalents.
In the middle of the 20th century, the discovery of the method of Carbon dating by Willard Frank Libby revolutionized the Archéologie. For the first time, by determining the quantity of radioactive carbon disappeared since their death, it is possible to give an estimate of the organic material age. However, the idea of the absolute dating is older: first discoverers of the Radioactivity, among which Pierre and Marie Curie and Ernest Rutherford, had already had the idea to use the “radioactive stop watch” to calculate geological ages. The real development of this technique was done into same as long as equipment of counting and of detection of the radioactive activity appeared and improved.
The absolute method, very diverse in its techniques, especially will open the way with others discovered after the first steps of Libby. Progress is also based on physical phenomena, which will widen considerably the field of materials (heated flint, ashes volcanic, dental enamel, etc) and of the datable events. These methods had a very important impact in many disciplinary fields where the age is a paramount element of the scientific knowledge (Archéologie, Paléontologie, Géologie, etc).
See too
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