Radiocarbon dating is commonly used to date
And lastly, the ratio of C-14 to C-12 in the atmosphere (and hence the ratio in organic remains) has fluctuated to a certain extent over the millennia, something that can lead to misleading discrepancies that need to be corrected for.
This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Some do not change with time and form stable isotopes (i.e.
those that form during chemical reactions without breaking down).
These are released as radioactive particles (there are many types).
This decay process leads to a more balanced nucleus and when the number of protons and neutrons balance, the atom becomes stable.
Others place mineral grains under a special microscope, firing a laser beam at the grains which ionises the mineral and releases the isotopes.
For geological purposes, this is taken as one year.Another way of expressing this is the half-life period (given the symbol T).
Archaeologists can then measure the amount of carbon-14 compared to the stable isotope carbon-12 and determine how old an item is.For example, it makes it possible to compare the ages of objects on a worldwide scale, allowing for indispensible comparisons across the globe.Before this, it was anyone's guess how different digs' timelines compared to one another over great distances.Prior to the development of radiocarbon dating, it was difficult to tell when an archaeological artifact came from.Unless something was obviously attributable to a specific year -- say a dated coin or known piece of artwork -- then whoever discovered it had to do quite a bit of guesstimating to get a proper age for the item.There's also still usually a wide window of time that an object can fall into.