The metaphysical poet, John Donne [1572-1631], once said: “… no man is an island, entire of itself; every man is a piece of the continent, a part of the main.” This sensible view of the need for cooperation among individuals applies to all academic research disciplines and Archaeology is no exception. The Antiquity of the human race and the details of the physical and cultural evolution of modern humans have been clarified greatly by the application of modern dating methods and modes of analysis, which have become an important part of Archaeology through the agency of Archaeometry. These analytical methods continue to develop and become more and more reliable as research progresses in both the various techniques themselves and their applications. This Issue of Physics in Canada contains some aspects of the applications of Physics to the discipline of Archaeometry, a subject that continues to grow rapidly in technique development and applications.
The application of physical principles to the understanding of culture and history began in the distant past. We can envision Og getting from Trog a black flint item, which is supposed to be obsidian; and, his percussionary test, hopefully not on Trog’s head, showing clearly that the item was not volcanic glass. In a more classical vein, we all remember Archimedes [287-212 BCE] discovering the way to measure the volume of an irregular object to help in the determination of its composition, through the relationship between volume and weight. This may have been one of the first experiments, which could be considered publishable as a contribution to Archaeometric research in the modern sense. It came none too soon as one of the oldest forms of forgery, the counterfeiting of coinage, that began circa 670 BCE, when coins were first minted in Lydia in Asia Minor had become a major concern throughout the Mediterranean World by the time of Archimedes. The touchstone first described by Theophrastus [371-287 BCE] is thought to have been invented at about this time [670 BCE] to assist in the regulation of coinage quality; and, texts from the library of Ashurbanipal [668-627 BCE] bear out this need as they discuss the making of silver-like alloys from the metal ingredients. Needles with known concentrations of the precious metals were also rubbed on the touchstone to determine the concentrations of the unknown [an example of these needles from Agricola’s De Re Metallica is shown on the front cover of this journal [upper right]].
The Renaissance was the beginning of modern archaeological thought with a shift in theoretical perspective from what may be termed alchemical mysticism to curiosity. This shift can be clearly seen in the written work of Hans Bauer (also known as Agricola) [1490-1555]. In De Re Metallica [1556], Agricola dismisses as a folk interpretation the celestial origin for ‘thunderstones’ and instead correctly attributes them as stone artifacts belonging to a people who lived in the past. His view is all the more remarkable when one realizes that he still held firmly the belief that good and bad gnomes inhabited mines [his research specialty] [1].
Thus, the work of Archimedes and the modernist Renaissance views of Agricola on objects are direct ancestors of some of the fine detective work on human artifacts and art objects summarized later in this issue of Physics in Canada by Dr. Paul Craddock of the British Museum. The possibility of finding objects that are created to deceive was just as real in the time of Archimedes or Agricola as it is now, for greed would appear to be an eternal human condition. For example, while still a very young man, Michelangelo [1475-1564] forged an antique marble cupid for his patron Lorenzo D’Medici [1449-1492].
Most of us are aware of the great interest that ancient cultures had in what we now call Astronomy. This interest has been more clearly presented to scholars and the interested public today with the discovery of ancient texts from Egypt, Mesopotamia, China and the Americas. This is a huge subject, which continues to fascinate both scholars and the public. Scholars now have at their disposal, thanks to several centuries of modern science, sophisticated tools that can be used in an attempt to understand these texts. As Professor John Steele points out, this is not as straightforward a process as one might expect and another feature of Archaeometry again becomes evident. This is the intensely interdisciplinary nature of the science of Archaeometry. Many scholars from a wide variety of disciplines must work together to achieve an understanding of the past by helping to answer those difficult questions posed by the archaeological data.
Many of the physical techniques, for analysing and dating objects and events, are byproducts from the discovery of radioactivity just over a hundred years ago. The development of the nuclear reactor has given the analyst a superb tool for finding out the composition of rare objects or artifacts by the various methods of neutron activation analysis. Canada is fortunate in this respect to have the Slowpoke reactor, developed at Chalk River, and the higher flux reactor at McMaster University. The contributions of these devices to analysis are summarized by Dr. Ron Hancock, one of the Canadian pioneers with over 30 years experience in this work. As in all the contributions the references are important for those who want to pursue further the art and science of Archaeometry.
Time has always been the great sorting mechanism in archaeological research. Dozens of classical authors in the first millennium BCE presented the concept of the succession of Ages from least technologically advanced to most advanced. The majority presented an argument for Stone, Bronze and Iron Ages, though variations with copper and gold were also put forward. Lucretius [95-53 B.C.] ably summarized these views. The principle of a systematic organization of archaeological materials started with the understanding of the Three Age System in the 16th Century by Michael Mercati [1541-1593], who was the Superintendent of the Vatican Gardens and advisor to Pope Clement VIII. The combination of his Renaissance education, his substantial mineral and fossil collections and his access to the newly acquired American ethnographic artifact collections permitted Mercati to formulate the foundations of modern archaeology. However, it was only in the early part of the 19th Century [1819] that Mercati’s concepts were applied rigorously to a museum collection. This was done specifically by Christian Thomsen [1788-1865], in Denmark, as a result of stimulation by a stray shot from one of Gambier’s ships of the line at Copenhagen in 1807 [2].
The dating of artifacts is of great importance to understanding the past and especially the more remote past during the evolution of the human race. It is in the chronometric dating of archaeological events that Archaeometry probably makes the most fundamental contribution to our knowledge of the past. A number of Canadian laboratories are at the forefront of Archaeometric Dating Research. These are the Argon-Argon Laboratory [Toronto] developed at Professor Derek York’s laboratory, the IsoTrace Radiocarbon and heavy element accelerator mass spectrometry laboratory [Toronto] directed by Professor A. E. Litherland, and the ESR Laboratory of Professor Jack Rink [McMaster] to mention but a few.
The story of potassium-argon or the argon-argon dating method, which relies on the radioactivity of 40K, is presented by Dr. Patrick Smith. The method is based on the well-known fact that most of the 40Ar in the atmosphere comes from 40K decay over geological time. It is possible with great care to measure the small number of additional 40Ar atoms created in certain samples, which lost all their argon by heating at some time in the past. This technique requires both a nuclear reactor and heating lasers in the modern form of the method.
During the past 25 years the measurement of long-lived radioactive isotopes such as 14C by mass spectrometry has been pioneered in Canada. However, as journal space precludes the telling of that story at this time, a reference alone [3] will have to suffice. The paper by Blockley et al., a group from Bradford University lead by Professor Mark Pollard, discusses the problems associated with the marine correction in radiocarbon dating in a North Atlantic and Arctic coastal or marine setting. It reviews the present state of knowledge on this very complicated issue and offers possible directions for future research. The paper is a reminder of the cooler air soon to come from the arctic, especially for those of us that had to handle this Archaeometry Issue during the heat that followed the great electricity blackout of 2003.
The steady natural radiation from the radioactive isotopes and cosmic rays in our environment can also be used to measure time because most minerals will store a portion of the radiation energy received in a manner that can be measured with modern technology, as described by Professor Jack Rink. This important but difficult method is now becoming more reliable for dating as the problems become better understood. These methods are now becoming valuable tools for art authentication, as mentioned by Dr. Paul Craddock.
Mass spectrometers can also be used for more than dating the remote past. The measurement of the abundance of residual lead isotopes from the decay of natural uranium and thorium clearly shows the natural variation in the abundances of lead isotopes from ores of different ages. This information, provided by Archaeometrists, can be exploited by the Archaeologist in an attempt to understand questions of provenance associated with the past human use of ores containing lead. Equally important for understanding ancient trade, such measurements can clarify the movement of the ores or ore products. This research is described eloquently by Professor Ron Farquhar, one of the Canadian pioneers with over a half century in lead isotope dating experience.
In addition to Canada’s leading role in Dating and Mass spectrometry research, Canada has also been near the forefront of Radar research in general and Ground Penetrating Radar (GPR) in particular. During World War II it was discovered that a plane’s radar altitude readings, being used when landing on the glaciers of Greenland, were at variance with the actual ice surface by hundreds to thousands of feet. The radar signals were seeing through the ice! This property of electromagnetic waves to propagate through materials with varying densities at measurable speeds has given birth to a GPR industry, which is alive and well in Canada. It is well described by Dr. Peter Annan’s paper. GPR is now being applied to archaeological problems with exciting results. Magnetics and resistivity measurements, once the mainstays of this aspect of archaeometric research, may have found their geophysical match in GPR.
J. W. Goethe [1749-1832] once argued the “… there is nothing new under the sun…” in which he was suggesting that everything has already been thought of by somebody. He may have been correct in a purely philosophical sense. However, we are sure you as a reader will appreciate, as you peruse these papers on the discipline of Archaeometry, that the mere thought of a technique or the application of a technique to a problem won’t get one very far without much hard work. Answering the questions of time, constitutional makeup, provenance, location or authenticity posed by the archaeologist, is a never-ending quest in the attempts to understand ancient human behaviour. This can only be done by successfully bridging the gap between the sciences and the humanities.
Larry Pavlish and Ted Litherland, Co-editors
[1] H. C. Hoover and L. H. Hoover, 1950. Translators of De Re Metallica, 1556, by Georgius Agricola. Dover Publications, Inc. New York, ISBN 0 486 60006 8 .
[2] G. Bibby, Testimony of the Spade 1956, A. Knopf, Inc., New York. Library of Congress 56-8916.
[3] H. E. Gove, From Hiroshima to the Iceman 1999, Institute of Physics Publishing, Bristol and Philadelphia, ISBN 0 7503 0557 6.
Editorial Board welcomes articles from readers suitable for, and understandable to, any practising or student physicist. Review papers and contributions of general interest are particularly welcome.