Radioactive dating technology
Isotopes of a particular element have the same number of protons in their nucleus, but different numbers of neutrons.
This means that although they are very similar chemically, they have different masses.
Scientists date igneous rock using elements that are slow to decay, such as uranium and potassium.
By dating these surrounding layers, they can figure out the youngest and oldest that the fossil might be; this is known as "bracketing" the age of the sedimentary layer in which the fossils occur.
Luckily, we can measure these fluctuations in samples that are dated by other methods.
Tree rings can be counted and their radiocarbon content measured.
Professor Willard Libby produced the first radiocarbon dates in 1949 and was later awarded the Nobel Prize for his efforts.
All rocks and minerals contain tiny amounts of these radioactive elements.
When living things die, they stop taking in carbon-14, and the radioactive clock is "set"!
Any dead material incorporated with sedimentary deposits is a possible candidate for carbon-14 dating.
Radioactive elements are unstable; they breakdown spontaneously into more stable atoms over time, a process known as radioactive decay.
Radioactive decay occurs at a constant rate, specific to each radioactive isotope.