Steven, thanks for clarifying, but I still have a problem.
>Richard,
> Thanks for the opportunity to clarify. I wrote that last paragraph in a
>hurry before rushing off for an appointment and didn't review it well. As
a
>rule of thumb, we generally cannot detect enough of a radiometric isotope
>after about 10 half-lifes to give a valid date. On a logrithmic curve, the
>amount of remaining isotope approaches infinity, however in reality you
>eventually decay the last atom. With better detection equipment, we may be
>able to see that last atom. BUT, since the decay is a random process and
>measurements are valid only on populations of atoms, any assigned dates
>based on the last few atoms would have very large error bars.
As I said, I'm no expert, but I'm pretty damn sure that, after 10
half-lives, you still have 1 in 1024 (2^10) of the original atoms. Doesn't
that follow from the definition of half-life? So how can you be down to the
last few atoms, unless you had only an insignificant number of atoms in the
first place?
Maybe I'm just ignorant about atomic decay. Please enlighten me.
>>From the table of data that I gave and using 10 half-lifes as a rule of
>thumb, the range of possible limits for the creation of elements found in
>our solar system would fall between a lower limit of 700 M.Y. and an upper
>limit of 7 B.Y.
>In my original post, I rounded that lower limit a little to let the last
>atom decay.
OK, that makes sense now, IF your rule of thumb is valid.
Richard Wein (Tich)
See my web pages for various games at http://homepages.primex.co.uk/~tich/
This archive was generated by hypermail 2b29 : Thu Mar 23 2000 - 17:23:56 EST