Absolute dating techniques in archaeology
C-14 dates are often published as dates 'before present' (the 'present' was fixed for analytical reasons at a single point, and the year AD 1950 was chosen for this) with the indication of the inaccuracy.
Thus, 3700 Tree-ring dating: Most trees produce a ring of new wood each year, visible as circles when looking at the cross section of a piece of wood.
Petrie was a scientific archaeologist, probably close to our first example.
The seriation method works because object styles change over time; they always have and always will.
The dating of remains is essential in archaeology, in order to place finds in correct relation to one another, and to understand what was present in the experience of any human being at a given time and place.
Inscribed objects sometimes bear an explicit date, or preserve the name of a dated individual. However, only a small number of objects are datable by inscriptions, and there are many specific problems with Egyptian chronology, so that even inscribed objects are rarely datable in absolute terms.
Petrie knew that styles of pottery seemed to come and go over time--in his case, he noted that some ceramic urns from the graves had handles and others had just stylized ridges in the same location on similarly shaped urns.
The contrast might also be drawn between two 'dimensions', the historical, and the archaeological, corresponding roughly to the short-term and long-term history envisaged by Fernand Braudel.
A good example of a change in artifact type is the development of hand-held PDAs from those first enormous cell phones. As an example of how change through time works, consider the different music recording methods that were used in the 20th century.
One early recording method consisted of large plastic disks which could only be played on a huge device called a gramophone.
The annual rings vary in size, depending on the weather conditions in each region, but they are similar for all trees of the same area.
If the sequence of rings is know for a certain area it is possible to fit in all new woods found and to date them very precisely.