This article explaining Carbon Dating by the BBC is the best I have read on this subject. It is easy to understand and yet all the elements are there. It is brief and concise.
Carbon dating has been used in all sorts of things including the ever mysterious Shroud of Turin. To this day, people and scientists still puzzle on the authenticity of the Shroud.
Carbon dating has not really worked to authentic the shroud. Apparently the shroud has been repaired many times in the past and newer threads were used, these thread were the ones given as samples to scientists for the carbon dating which of course would show and give the illusion that the shroud is a fake, or rather not the one used by Jesus of Nazareth.
The mystery lives on.
Be that as it may, carbon dating has been used in so many things which has been more than useful.
The Story of Carbon Dating
Certain chemical elements have more than one type of atom. Different atoms of the same element are called isotopes. Carbon has three main isotopes. They are carbon-12, carbon-13 and carbon-14. Carbon-12 makes up 99% of an atom, carbon-13 makes up 1% and carbon-14 – makes up 1 part per million. Carbon-14 is radioactive and it is this radioactivity which is used to measure age.
Radioactive atoms decay into stable atoms by a simple mathematical process. Half of the available atoms will change in a given period of time, known as the half-life. For instance, if 1000 atoms in the year 2000 had a half-life of ten years, then in 2010 there would be 500 left. In 2020, there would be 250 left, and in 2030 there would be 125 left.
By counting how many carbon-14 atoms in any object with carbon in it, we can work out how old the object is – or how long ago it died. So we only have to know two things, the half-life of carbon-14 and how many carbon-14 atoms the object had before it died. The half-life of carbon-14 is 5,730 years. However knowing how many carbon-14 atoms something had before it died can only be guessed at. The assumption is that the proportion of carbon-14 in any living organism is constant. It can be deduced then that today’s readings would be the same as those many years ago. When a particular fossil was alive, it had the same amount of carbon-14 as the same living organism today.
The fact that carbon-14 has a half-life of 5,730 years helps archaeologists date artefacts. Dates derived from carbon samples can be carried back to about 50,000 years. Potassium or uranium isotopes which have much longer half-lives, are used to date very ancient geological events that have to be measured in millions or billions of years.