Concise Oxford Dictionary of Archaeology (590 page)

 
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A technique for determining the absolute date of organic matter developed by Willard
LIBBY
in 1949 and based on the fact that all living organisms contain a small but constant proportion of the radioactive isotope of carbon,
¹⁴
C. When the organism dies the
¹⁴
C is no longer replenished from the environment and what is present at the time of death decays at a constant rate. The half-life of
¹⁴
C was calculated by Libby as being 5568 years. By measuring the radioactivity of the carbon remaining in a specimen its age can be calculated; radiocarbon determinations (usually expressed as an age BP or as RCYBP) have to be calibrated using curves derived from tree-ring chronologies to give calendar dates (usually expressed as
bc
/
ad
or cal.
bc
/cal.
ad
). Radiocarbon dating is useful back to about 70000 years ago.

 
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See
X–RADIOGRAPHY
.

 
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Blanket term used to refer to methods of providing absolute dates for archaeological materials based on the decay of radioactive isotopes. See
RADIOCARBON DATING
;
URANIUM SERIES DATING
; and
POTASSIUM–ARGON DATING
.

 
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See
RESEARCH ASSESSMENT EXERCISE
.

 
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King of the East Angles, who accepted Christianity at the prompting of
AETHELBERHT
of Kent, though continuing to worship his old gods. He was recognized as Bretwalda, ‘high king’, of the English. It is likely, though not certain, that the great ship-burial of Sutton Hoo, Suffolk, was the tomb of Raedwald. He died
c.
ad 625.

 
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