Carbon dating to

Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).

The use of various radioisotopes allows the dating of biological and geological samples with a high degree of accuracy.

Libby had first started using the dating method in 1946 and the early testing required relatively large samples, so testing on scrolls themselves only became feasible when methods used in the dating process were improved upon. Davies made a request to date a number of scrolls, which led to a series of tests carried out in Zurich on samples from fourteen scrolls.

Among these were samples from other sites around the Dead Sea, which contained date indications within the text to supply a control for the carbon dating results.

Desmond Clark (1979) wrote that were it not for radiocarbon dating, "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation" (Clark, 1979:7).

Writing of the European Upper Palaeolithic, Movius (1960) concluded that "time alone is the lens that can throw it into focus".

This calibrated range of dates is represented in the last column, given with a 2-sigma error rating, which means at 95% confidence.

With the exception of the first text from Wadi-ed-Daliyeh, the texts in the table below are only those from the caves around Qumran.

The following table shows all the Qumran-related samples that were tested by Zurich (Z), Tucson (T) and Libby (L).

The column headed "14C Age" provides a raw age before 1950 for each sample tested.

However, radioisotope dating may not work so well in the future.

Anything that dies after the 1940s, when Nuclear bombs, nuclear reactors and open-air nuclear tests started changing things, will be harder to date precisely.

By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.

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