By measuring the ratio of the amount of the original radioactive element to the daughter isotope, scientists can determine how many half-lives the element has undergone and from there can figure out the absolute age of the sample.
The half-lives of several radioactive isotopes are known and are used often to figure out the age of newly found fossils.
(Aside, my dad doesn’t know how old I am, he usually misses by about two years, giving him an error of almost 5%.) Not only, is this not a ‘false assumption’. Oh and here’s a link to the Table of Contents for this set of creationist misconceptions.
Perhaps the most widely used evidence for the Theory of Evolution through Natural Selection is the fossil record.
In this way, items of unknown age can be tested and an age determined to a reasonable degree of accuracy. More tomorrow where we explore the concept of isochron dating and how it neatly destroys most of the rest of these ‘issues’.
Half-life is defined as the time it takes for one-half of a radioactive element to decay into a daughter isotope.
As radioactive isotopes of elements decay, they lose their radioactivity and become a brand new element known as a daughter isotope.
As a result, rocks that record its earliest history have not been found and probably no longer exist.
Nevertheless, there is substantial evidence that the Earth and the other bodies of the Solar System are 4.5-4.6 billion years old, and that the Milky Way Galaxy and the Universe are older still.