Radioactive carbon dating kids
Now the curve extends (tentatively) to 50,000 years.Radiocarbon dates are presented in two ways because of this complication.
The total mass of the isotope is indicated by the numerical superscript. Carbon has different isotopes, which are usually not radioactive.Plants take up atmospheric carbon dioxide by photosynthesis, and are eaten by animals, so every living thing is constantly exchanging carbon-14 with its environment as long as it lives. In 1958 Hessel de Vries showed that the concentration of carbon-14 in the atmosphere varies with time and locality.The calibrated date is our “best estimate” of the sample’s actual age, but we need to be able to return to old dates and recalibrate them because new research is continually used to update the calibration curve.The second difficulty arises from the extremely low abundance of C, making it incredibly difficult to measure and extremely sensitive to contamination.The relatively short-lived C taken into organic matter is also slightly variable. However, under about 20,000 years the results can be compared with dendrochronology, based on tree rings.
For the most accurate work, variations are compensated by means of calibration curves.
Tree rings can be counted and their radiocarbon content measured.
From these records a “calibration curve” can be built (see figure 2, below).
While the lighter isotopes C has decayed that what remains can no longer be measured. In 5,730 years half of the C in the atmosphere, and therefore in plants and animals, has not always been constant.
Radioactive decay can be used as a “clock” because it is unaffected by physical (e.g. For instance, the amount varies according to how many cosmic rays reach Earth.
This is affected by solar activity and the earth’s magnetic field.