Age of a rock using radiometric dating
Science cannot predict which particular K-40 atom in this sample will decay and which will not during the next 1.25 billion years, but that is OK. It is like flipping a huge amount of coins: you know that the likelihood, or probability, is that you will end up with half of them heads up, but you have no idea which particular one will end up heads, or if even half of them will be heads for sure. Can geologists say that once the amount of K-40 isotopes in the sample has reduced to half its original amount, 1.25 billion years will have gone by?
Yes — as long as they use a big enough sample so statistical fluctuations average out.
Geologists have a much harder job keeping track of time.
Studying the Earth and its evolution, they work with time scales of thousands to billions of years.
If so, try not to worry: This science project will only use its graphical representation, known as the decay curve .It is now time to explore why geologists are so interested in these radioactive decay processes as a means of dating objects. This example might help clarify the processes and terms just introduced: Looking at the parent isotope potassium-40 (abbreviated as K-40) that decays into the daughter isotope argon-40 (abbreviated as Ar-40), scientists measured the half-life time to be 1.25 billion years.But before we do, can you list some characteristics a good clock should have? This means that half of the K-40 atoms existing today will have made the transformation to Ar-40 at some point during the next 1.25 billion years, no matter what weather they experience, pressure they undergo, or any other outside circumstances.Create a model of radioactive decay using dice and test its predictive power on dating the age of a hypothetical rock or artifact. That is what we encounter in our daily lives, right?The Earth orbits the Sun in about one year's time, the Earth rotates on its axis every 24 hours, 60 ticks of the second hand on a clock indicates 1 minute has passed.
Search for age of a rock using radiometric dating:
The isotope that is created during the process (here argon-40) is called the daughter isotope.