The radioactive isotope carbon-14 is created in the upper atmosphere when cosmic-ray particles from outer space strike nitrogen atoms and transform them into radioactive carbon.
Some of the carbon-14 might find its way into living creatures.
It was an anxious time for scientists whose reputation for accurate work was on the line.
But what looks like unwelcome noise to one specialist may contain information for another.
Comparing the old wood with modern samples, he showed that the fossil carbon could be detected in the modern atmosphere.(5) Through the 1950s and beyond, carbon-14 workers published detailed tables of dates painstakingly derived from samples of a wondrous variety of materials, including charcoal, peat, clamshells, antlers, pine cones, and the stomach contents of an extinct Moa found buried in New Zealand.(6) The measurements were correlated with materials of known dates, such as a well-documented mummy or a log from the roof of an old building (where tree rings gave an accurate count of years).
The results were then compared with traditional time sequences derived from glacial deposits, cores of clay from the seabed, and so forth.
As for still earlier periods, carbon-14 dating excited scientists (including some climate scientists) largely because it might shed light on human evolution the timing of our development as a species, and how climate changes had affected that.(2) It was especially fascinating to discover that our particular species of humans arose something like 100,000 years ago, no doubt deeply influenced by the ice ages.(3) A few scientists noticed that the techniques might also be helpful for the study of climate itself.
From its origins in Chicago, carbon-14 dating spread rapidly to other centers, for example the grandly named Geochronometric Laboratory at Yale University.
For example, Hans Suess relied on a variety of helpers to collect fragments of century-old trees from various corners of North America.
He was looking for the carbon that human industry had been emitting by burning fossil fuels, in which all the carbon-14 had long since decayed away.
Making the job harder still, baffling anomalies turned up.
The carbon-14 dates published by different researchers could not be reconciled, leading to confusion and prolonged controversy.
This was all the usual sort of laboratory problem-solving, a matter of sorting out difficulties by studying one or another detail systematically for months.