Old can radiocarbon dating
It isn't possible to investigate all of a junkyard, so we'll pick a representative sample of the deposit.
We take our samples back to the laboratory, and count the kinds of artifacts in them, and discover that each of the junkyards have broken pieces of musical recording methods in them--old broken records, pieces of stereo equipment, 8-track cassette tapes.
The gramophone sat in your parlor and certainly couldn't be carried along with you and your earbobs. When 78 rpm records first appeared on the market, they were very rare.
When they became popularly available, you could find them everywhere; but then the technology changed and they became rare again. Archaeologists investigate trash, not shop window displays, so we measure things when they are discarded; in this example, we're going to use junkyards.
You would expect a large number in one closed when 78s were popular and a small number again after 78s were replaced by a different technology.
You might find a small number of 78s for a long period after they were pretty much done.
Archaeologically, you would expect no 78s to be found in a junkyard that was closed before 78s were invented.
There might be a small number of them (or fragments of them) in the junkyard which stopped taking junk during the first years 78s were invented.
For this seriation demonstration, we're going to assume that we know of six junkyards (Junkyards A-F), scattered in the rural areas around our community, all dated to the 20th century.Seriation, also called artifact sequencing, is an early scientific method of relative dating, invented (most likely) by the Egyptologist Sir William Flinders Petrie in the late 19th century.Petrie's problem was that he had discovered several predynastic cemeteries along the Nile River in Egypt that seemed to be from the same period, but he needed a way to put them in chronological order.Microsoft Excel (TM) has created for us a lovely stacked bar graph for us.Each of the bars in this graph represents a different junkyard; the different colored blocks represent percentages of artifact types within those junkyards.