Scientists must assume how much carbon-14 was in the organism when it died.Complicating matters is the fact that Earth’s carbon-14 concentrations change drastically based on various factors.Question: "Is carbon dating a reliable method for determining the age of things?
Tiny variations within a particular sample become significant enough to skew results to the point of absurdity.
Carbon dating therefore relies on enrichment and enhancement techniques to make smaller quantities easier to detect, but such enhancement can also skew the test results. As a result, carbon dating is only plausible for objects less than about 40,000 years old.
The other major factor affecting the results of carbon dating is gauging the original proportion of carbon-14 itself.
Carbon dating is based on the loss of carbon-14, so, even if the present amount in a specimen can be detected accurately, we must still know how much carbon-14 the organism started with.
Likewise, different living things absorb or reject carbon-14 at different rates.
Two plants that died at the same moment, but which naturally contained different levels of radiocarbon, could be dated to drastically different times.
Several factors affect radiocarbon test results, not all of which are easy to control objectively.
For this reason, it’s preferable to date objects using multiple methods, rather than relying on one single test.
For example, a steel spearhead cannot be carbon dated, so archaeologists might perform testing on the wooden shaft it was attached to.
This provides good information, but it only indicates how long ago that piece of wood was cut from a living tree.
Most archaeological items can’t be directly carbon dated, so their dating is based on testing done on nearby objects or materials.