The only problem is that we only know the number of daughter atoms now present, and some of those may have been present prior to the start of our clock. The reason for this is that Rb has become distributed unequally through the Earth over time.
We can see how do deal with this if we take a particular case. For example the amount of Rb in mantle rocks is generally low, i.e. The mantle thus has a low If these two independent dates are the same, we say they are concordant.
But crystals from supposedly billion-year-old granites are packed with helium.
The best explanation for this is that radioactive decay that would normally take billions of years actually occurred very quickly.
We can also construct a Concordia diagram, which shows the values of Pb isotopes that would give concordant dates.
The Concordia curve can be calculated by defining the following: ).
Radioactive polonium-210 emits particles to quickly become lead-206.Results like these prompted a team of seven creation researchers to investigate the causes of incorrect radioisotope age estimates.They found two clues in granite rock that are best explained by radioisotopes that decayed much faster in the past than they do today.Trapped helium and short-lived polonium radiohalos present in granite suggest that radiodecay rates were once much higher than they are today.Plus, significantly older radiodates for rocks of a known age show that radiometric dating is not reliable.