The universe is full of naturally occurring radioactive elements.Radioactive atoms are inherently unstable; over time, radioactive "parent atoms" decay into stable "daughter atoms." When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.Fossils are generally found in sedimentary rock not igneous rock.Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years.
You probably have seen or read news stories about fascinating ancient artifacts.At an archaeological dig, a piece of wooden tool is unearthed and the archaeologist finds it to be 5,000 years old.A child mummy is found high in the Andes and the archaeologist says the child lived more than 2,000 years ago.How do scientists know how old an object or human remains are?
What methods do they use and how do these methods work?
In this article, we will examine the methods by which scientists use radioactivity to determine the age of objects, most notably carbon-14 dating.