What’s in an Age?


Firstly, why should the age of the Earth matter…

OK, here’s an interesting read about the vandalizing of a beloved rock formation. Aside from the senseless act described by the headline, I can’t help but entertain a nagging suspicion that most of us will look at it and not give a second thought to this provocative question: How did someone decide the age of these rocks?

How does anyone come to believe in the age of rocks, fossils, and other artifacts of supposed great age?

One method used is to measure the ratio of parent-to-daughter elements in the material being examined. Today, and under controlled conditions, radioactive elements decay at predictable rates. This predictable decay rate is known as the half life.

Uranium-238, for instance, decays into stable lead (Pb) with a half life of about 4.47 billion years. That means that if a certain rock had a million U-238 atoms, then about 4.47 billion years later, roughly 500,000 of those atoms would have decayed into stable Pb.

By measuring the present ratio of U-238 to Pb in a certain rock, a conclusion is reached about the age of that rock. That’s the basic concept as taught from middle school through graduate school.


Are there other factors or processes that should be considered when using decay rates to evaluate the age of an item?

What are the unstated assumptions used in reaching conclusions about the passage of time from the ratios of radioactive elements?

Are there other known processes can alter predicted decay rates?

How many of us, including those with advanced degrees in science, have ever been taught anything about these factors & assumptions, or anything about observable, naturally occurring processes that can produce the almost instantaneous decay of unstable elements?

Lastly, why should the age of a rock matter to any of us?

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