Radiometric dating becomes impossible when consolidating information in excel
rely heavily on the uranium/thorium/lead radiometric dating methods.
Because it is not generally appreciated that the assumptions on which the radiometric estimates are based are a virtually impossible sequence of events, let us refresh our minds on the fundamentals of the method by turning to the hourglass analogy (Fig. This system of measuring time works well providing that: Since radioactive decay constants are believed to be unalterable, the requirement of an absolutely reproducible rate is hopefully met.
The radiometric dating method is basically an extrapolation of the form shown in Fig. If the decay constant is known with great accuracy, an extrapolation over one or two thousand years may be regarded as quite reasonable. It should be obvious that the further one projects present rates, the more likely one is to be quite wrong. era started about 1955 with the publication of a classic paper by Patterson In spite of cautions and scepticism advised by the authors this number has been widely and enthusiastically accepted and is usually quoted as if the evidence was decisive and conclusive. Lead-206 and lead-207 are known daughter products from the decay of uranium-238 and uranium-235, respectively.
Up until 1972 these could be explained as being contaminated with radiogenic lead from uranium and thorium decay.
In 1972, however, Gale showed unequivocally that there is by no means sufficient uranium and thorium to account for what could previously have been called radiogenic lead.
They estimated the age of the Earth by substituting the lead isotope ratios of certain meteorites in the Holmes-Houtermans equation.
In this equation the primordial lead ratios are required.
Despite this, the momentum gained in the two decades prior to 1972 has made 4.5 b.y.
a popularly accepted “universal constant” even though the foundations on which it was based have been virtually removed.These ratios for many lead ores are plotted in Fig. The lowest ratios are taken to be the most ancient ores, formed at the beginning, billions of years ago and separated from further radiogenic enrichment. They show that widespread contamination and differentiation from various sources of lead have occurred during the more than one thousandfold concentration into the present lead ore deposits. There is no discontinuity whatever between results lying in the time clock zone and those lying in the alteration zone. Since there is no reason why the alteration zone should not extend into what is classified as the time clock zone (apart from a belief in 4.5 b.y.), the majority of the data can be explained as indicating a history of geochemical alteration.Higher ratios are formed as the lead is fed by ageing uranium ore bodies. old lead fed continuously by uranium occurs at a lead-206 to lead-204 ratio of 18.5, which is taken as the present ratio for common lead. 3 since they have negative ages, that is, ages extending billions of years into the future, in some cases. Therefore the ores lying in the time clock zone are not necessarily any more a reflection of age than those lying in the alteration zone and ones lying in the alteration zone cannot possibly be time indicators.Lead-206 and lead-207 are also believed to be present in primordial lead since there is insufficient uranium to account for all the lead.Just how much lead-206 and 207 were present at the beginning, nobody knows. As a uranium ore ages, the ratio of lead-206 to lead-204 increases as does the ratio of lead-206 to lead-207.Since the lead in meteorites can no longer be ascribed to uranium/thorium decay, it may also be taken to represent primordial lead.Tags: Adult Dating, affair dating, sex dating