Help us reduce the maintenance cost of our online services.
Because your computer is running an older version of internet browser, it no longer meets the features of modern websites.
A copy of this paper may be found in the Radiocarbon Home Page The radiocarbon age of a sample is obtained by measurement of the residual radioactivity. T (National Institute of Standards and Technology; Gaithersburg, Maryland, USA) Oxalic Acid I (C). The activity of 1890 wood is corrected for radioactive decay to 1950.
This is calculated through careful measurement of the residual activity (per gram C) remaining in a sample whose age is Unknown, compared with the activity present in Modern and Background samples. Thus 1950, is year 0 BP by convention in radiocarbon dating and is deemed to be the 'present'.
Many examples from literature show that the zero-reset assumption is not always valid.
Volcanic ejecta of Mount Rangitoto (Auckland, New Zealand) was found to have a potassium-40 age of 485,000 years, yet trees buried within the volcanic material were dated with the carbon-14 method to be less than 300 years old.
Specimens would then look much older than they actually are.
d) Even if the rate of decay is constant, without knowledge of the exact ratio of carbon-12 to carbon-14in the initial sample, the dating technique is subject to question.
While there is no proof that the rates were different in the past than they are today, there is also no proof that they were the same.
Thus radioactive dating relies purely on assumptions.
Carbon-14 comes from nitrogen and is independent of the carbon-12 reservoir.