Before applying the C-14 method to some newly discovered "materials",
we need to examine one of its assumptions: that the amount of C-14 produced
in the Earth's upper atmosphere from cosmic rays striking N-14 is constant
over time. It turns out that the production of C-14 changes somewhat
from year to year because of variations in incoming cosmic radiation.
Increased solar flare activity increases C-14 with higher amounts of
C-14 found in organisms that lived during those times.
To compensate for variations in C-14, scientists have developed
calibration curves from studies of tree rings of the ancient Bristlecone
Pines of the White Mountains of California and oak trees of Germany and
Ireland. Through these studies (dendrochronology), calibration data has
been developed that goes back nearly 11,000 years.
The applet below compares actual tree ring ages (from counting) with
the equivalent Radiocarbon age. Use your mouse to drag on the wood core
to set the variation tree rings between 1000 to 400 years old.
