This approach helps to order events chronologically but it does not provide the absolute age of an object expressed in years.
Relative dating includes different techniques, but the most commonly used are soil stratigraphy analysis and typology.
For those researchers working in the field of human history, the chronology of events remains a major element of reflection.
Archaeologists have access to various techniques for dating archaeological sites or the objects found on those sites.
The central rings of this older tree may then be compared with the outer rings or a yet older tree, and so on until the dates reach back into prehistory.
Problems that arise are when climatic variation and suitable trees (sensitive trees react to climatic changes, complacent trees do not) are not be present to produce any significant and recognizable pattern of variation in the rings.
During the first half of the 20th century, the astronomer A. Douglass founded the Laboratory of Tree-Ring Research at the University of Arizona.
These variations, given favorable conditions, form a consistent pattern; and sections or cores taken from beams in ruins have been matched to provide a long chronology over large areas.
The method is based on the principle that trees add a growth ring for each year of their lives, and that variations in climatic conditions will affect the width of these rings on suitable trees.
In his Trattato della Pittura (Treatise on Painting), Leonardo da Vinci was the first person to mention that trees form rings annually and that their thickness is determined by the conditions under which they grew. S., Alexander Catlin Twining (1801–1884) suggested in 1833 that patterns among tree rings could be used to synchronize the dendrochronologies of various trees and thereby to reconstruct past climates across entire regions.
During the latter half of the nineteenth century, the scientific study of tree rings and the application of dendrochronology began.