In Worlds in Collision I claimed that the time since the last glaciation needs to be drastically shortened: the figure considered valid in 1950, the year Worlds in Collision was published, was still Lyells of 100 years earlier, namely 35 thousand years. previously this maximum advance had been assumed to date from about 25,000 years ago, actually 35,000 if one looks up the literature of the time. found that, as I also claimed, another advance of ice took place only 3,500 years ago.
Libby found (and I quote Frederick Johnson, who participated in his volume, Radiocarbon Dating) that the advance of the ice occurred about 1 1,000 years ago . A few years later Rubin and Suess of the Geological Survey of the U. The second confirmation came concerning the age of the petroleum. The surprising fact was that oil was found there in Recent sediment and must have been deposited during the last 9,200 years. (Emphasis added.) Actually I asked Libby whether he would see to it that petroleum should be subjected to tests and it was he who drew my attention to the work done by Smith.
When objects of the Old Kingdom and Middle Kingdom of Egypt yielded carbon dates that appeared roughly comparable with the historical dates, Libby made his method known.
With initial large margin of error and anything that did not square with expectation, judged as contaminated, the method appeared to work and was hailed as completely reliablejust as the atomic clock is reliableand this nobody doubted.
The correctness of the method depends greatly on the condition that in the last 40 or 50 thousand years the quantity of water in the hydrosphere (and carbon diluted in it) has not substantially changed. The method depends also on the condition that during the same period of time the influx of cosmic rays or energy particles coming from the stars and the sun has not suffered substantial variations.
To check on the method before applying it on various historical and paleontological material, Libby chose material of Egyptian archaeology, under the assumption that no other historical material from over 2,000 years ago is so secure as to its absolute dating.
Folghereiter done at the turn of the century on Attic and Etruscan pottery: he found that the polarity was reversed in the eighth century before the present, era.
According to the so-called high chronology, the transition occurred around 1000 or 980 B.
But as the method was refined, it started to show rather regular anomalies.
First, it was noticed that, when radiocarbon dated, wood grown in the 20th century appears more ancient than wood grown in the 19th century.
Therefore the claim was made that the magnetosphere around the earth, discovered in 1958, suffered occasional weakening, thus allowing more cosmic rays to pass it and to hit the nitrogen atoms in the upper atmosphere, changing them to radiocarbon.
It was further claimed that the magnetic field of the earth might have reversed its polarity in the last 40 thousand years, a phenomenon known to have happened in geological epochs.