Any contamination of a sample by outside carbon (even from the researcher's fingerprints) had to be fanatically excluded, of course, but that was only the beginning.
Delicate operations were needed to extract a microscopic sample and process it.
Climate science required the invention and mastery of many difficult techniques.
These had pitfalls, which could lead to controversy.
A stronger field would tend to shield the planet from particles from the Sun, diverting them before they could reach the atmosphere to create carbon-14.
and "not very attractive."(8) However, solar specialists knew that the number of particles shot out by the Sun varies with the eleven-year cycle of sunspots.
The results were then compared with traditional time sequences derived from glacial deposits, cores of clay from the seabed, and so forth.After a creature's death the isotope would slowly decay away over millennia at a fixed rate.Thus the less of it that remained in an object, in proportion to normal carbon, the older the object was.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.Also, the Sun’s own magnetic field varies with the cycle, and that could change the way cosmic particles bombarded the Earth.In 1961, Minze Stuiver suggested that longer-term solar variations might account for the inconsistent carbon-14 dates. Libby, for one, cast doubt on the idea, so subversive of the many dates his team had supposedly established with high accuracy.(9) Suess and Stuiver finally pinned down the answer in 1965 by analyzing hundreds of wood samples dated from tree rings.In 1958, Hessel de Vries in the Netherlands showed there were systematic anomalies in the carbon-14 dates of tree rings.His explanation was that the concentration of carbon-14 in the atmosphere had varied over time (by up to one percent).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.To get a mass large enough to handle, you needed to embed your sample in another substance, a "carrier." At first acetylene was used, but some workers ruefully noted that the gas was "never entirely free from explosion, as we know from experience."(4) Ways were found to use carbon dioxide instead.Frustrating uncertainties prevailed until workers understood that their results had to be adjusted for the room's temperature and even the barometric pressure.One application was a timetable of climate changes for tens of thousands of years back.