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& most people are not in the half they think they are in

I’ve always thought these lyrics are spot on.......

“They say that three percent of people
Use five to six percent of their brain
Ninety-seven percent use just three percent
And the rest goes down the drain
I'll never know which one I am
But I'll bet you my last dime
Ninety-nine percent think we're three percent
One-hundred percent of the time”

Todd Snider - statistician’s blues
 
Well, point being, if the uranium existed shortly after the universe happened, wouldn't that be the beginning of its life?
As opposed to when someone stumbled on a deposit within human existence?
I reckon "half life" is indeed an arbitrary time frame term...

Just saw this and have to bring it back up

Nope it starts the moment the element comes into existance. Every element heavier than iron was created in supernovae billions of years after the big bang so that's why the radioactive ones still exist. The way they can prove this is that the measured half life of U-235 is shorter than U-238 and on earth they exist in the average proportions of 99.2% U-238 and 0.8% U-235. Since they are formed by the same process they must have originally existed in equal proportions, and based on that they can calculate when the uranium on earth was formed.

Half life doesn't start when we start observing it, but our measurement of the decay constant does. Half life is a calculated value for long lived isotopes based on a simple decay equation that uses a measured rate of decay.
 
Time for a reminder: Any discussion of political, religious, or other (non-brewing related) potentially divisive subjects is allowed only in the "Debate" forum. Posts have been, and will continue to be, deleted in this, and other threads not in the debate forum.

doug293cz
HBT Moderator
 
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