These fluctuations in the historic radiocarbon clock mean that to find the calendar dates of artifacts, scientists need methods and samples that can independently verify the amount of carbon-14
in the atmosphere at a given time.
These nuclear tests took place during the period 1955-1963, and led to a very strong increase in the amount of radioactive carbon-14
in the atmosphere.
As a result of variations in the production of carbon-14
in the atmosphere through time, radiocarbon years have a certain percentage of error, depending on age and type of material.
Heinemeier and colleagues made this discovery by taking advantage of carbon-14
spikes resulting from post WWII nuclear bomb tests.
Within that component, about one in a trillion of the carbon atoms is carbon-14
(C-14), a radioactive isotope produced by cosmic rays at high altitudes.
Analysis of two ancient trees found a surge in carbon-14
- a carbon isotope that derives from cosmic radiation - which occurred just in AD 774 and AD 775, the team led by Fusa Miyake of Nagoya University report in the journal Nature on Sunday.
The team extracted and purified samples of two MeO-PBDEs, MeO-BDE-47 and MeO-BDE-68, and measured the ratios of the isotopes carbon-14
and carbon-12 in each sample.
Scientists at Karolinska Institutet measured the radioactive isotope carbon-14
and showed that fat cells in overweight people have a higher capacity for storing fats but a lower capacity for ridding themselves of them.
For instance, some measurable traces of cosmic rays come in the form of carbon-14
, an invaluable tool for dating archeological specimens.
Inside the Scrolls" provides a unique illustrated catalog of the contents of all 11 caves, including detailed analysis of every major scroll, and considers the methods of interpretation employed, including carbon-14
dating, paleography, and computer reconstruction.
is an unstable isotope formed in the upper atmosphere through the action of cosmic rays, and its steady decay is the basis for carbon-dating of organic material.
The organic carbon in the soils has been stripped away by wind or water, so scientists can't use carbon-14
dating to estimate when those wet spells might have occurred, says Muhs.