Relative dating helps determine what came first and what followed, but doesn't help determine actual age.
Radiometric dating, or numeric dating, determines an actual or approximate age of an object by studying the rate of decay of radioactive isotopes, such as uranium, potassium, rubidium and carbon-14 within that object. This rate provides scientists with an accurate measurement system to determine age.
Scientists measure the proportion of carbon-14 left in the organism to determine its age.
Our planet inherits a large number of artifacts and monuments bestowed upon us by older historic civilizations.
For example, carbon dating is used to determine the age of organic materials.
Once something dies, it ceases taking in new carbon-14, and the existing carbon-14 within the organism decays into nitrogen at a fixed rate.
Before radiometric dating (or other methods of absolute dating like counting tree rings) it was difficult to determine the actual age of an object.
The circumstances of the object may allow one to say that one object is older than another without being able to assign a particular age to the objects.Very often historical evidence is found in layers and older layers are further down that the top layers.For example: If an archaeologist is studying past civilizations, the archaeologist may be able to say that in a particular location the ruins of one civilization were found to have been built on another and so the layers unearthed in an excavation convey the sequence of historical occupations without revealing the actual dates.These principles are the principle of superposition, the principle of original horizontality, the principle of cross-cutting relationships, and the principle of inclusions.The principle of superposition is defined as in the environment of an undisturbed layer of sedimentary rocks; the layers on the bottom are older than the layers towards the top.