[time-nuts] Disciplining Rubidium

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Apr 24 02:51:40 EDT 2008

SAIDJACK at aol.com wrote:
> Hi Bruce,
> last chemistry/physics class is a while back :) I guess a half life of 50  
> Billion years means it's not really radiating much?
> No problem with Cesium then either, I guess the radiation levels must be  
> really really low?
> thanks,
> Said

Calculating the number of atoms that decay per second in a particular 
sample is almost trivial:
Divide the mass of the sample (in grams) by the atomic weight, multiply 
the result by Avogadro's number and then divide by the number of seconds 
in 5E10 years.

Result for a 10gm sample of Rb87

No of atoms present ~ 6.02E23 x 10/85 ~ 7E22
No of seconds in 5E10 years ~ 1.5E18
Thus number atoms in the sample decaying per second ~47,000.
Equivalent electron current ~ 7.6fA.

One saving grace is that beta particles (electrons) are essentially 
stopped by a piece of paper, just dont eat the stuff.


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