In the text on page 202, it talks about parent isotopes and how they found 950 and daughter isotopes 50 count. I am so confused. I know how it works, but why is the parent isotope larger than the daughter when I thought that the daughter isotopes grew and the parent isotopes decline in number? The answer is probably right there in front of me but I'm just not seeing it!

-- Tina Miller (sultice@msn.com), March 29, 2001

Answers

What they are saying, is that since they know the ratio of rubidium to strontium decay, and there is 50 strontium atoms (using this info. along with being able to detect 950 rubidium atoms) tells them how long it has been decaying for. I believe that you are correct, as time goes bye; there will be more and more daughter atoms. So, if they took another reading, after some time had passed, they might find 920 stronium atoms and 80 rubidium atoms.

-- Terry McCall (mccall@oswego.edu), April 03, 2001.

What i believe the book is trying to say is that you don't need a full half life to pass in order to date the rock. only a small amount of the daughter isotope needs to be present in order to correctly approxiamate the date of the rock. since we already know the half life of the isotope, we only need to set up a ratio to figure out the age of the rock.

-- craig garrison (seniorchicano@yahoo.com), April 04, 2001.