This produces radiation and is particularly prominent with larger atoms that are easily able to fall apart spontaneously, leading to new elements or a lighter form of the original element.The time it takes for half of the atoms of an element in a sample to decay is known has its half-life.Other isotope combinations used in dating include samarium-neodymium, rubidium-strontium and uranium-lead.Where isotope analysis is not suitable, scientists can also use optically stimulated luminescence dating.If a particular fossil found in a rock layer comes from a known period, it can give an indication of the age of the rock layer and other fossils found nearby.These fossils are known as “index fossils” and include trilobites and ammonites.This type of dating works on the principle that an object’s age can be determined by analysing the surrounding geology.
If this is the case, a proton or a neutron can be released as the atom rearranges itself into a more stable isotope.
Carbon-14, an isotope of the common carbon-12, has a half-life of around 5,730 years.
It’s found throughout the food chain – it’s taken up by plants for photosynthesis, then eaten by herbivores which are, in turn, eaten by carnivores – so is usually used to date samples which were once alive, from woolly mammoths to Egyptian mummies.
If you want to know the precise age of something, absolute dating techniques are the only option.
They work by analysing the activity of elements and their decay over time.