
How Science Figured Out the Age of the Earth - Libertatea
http://www.scientificamerican.com/article.cfm?id=how-science-figured-out-the-age-of-the-earth
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hdivider
A really good book on this is _The Dating Game: One Man 's Search for the Age
of the Earth_

[http://www.amazon.com/The-Dating-Game-Search-
Earth/dp/052189...](http://www.amazon.com/The-Dating-Game-Search-
Earth/dp/0521893127/ref=sr_1_2?ie=UTF8)

by Cherry Lewis [0].

It's an informative read. Especially the stuff about the actual calculations.
It's fun to realise how massively the early approaches (salinity, heat
transfer considerations, etc.) were blown out of the water by good old nuclear
decay (Rubidium->Strontium, as I recall).

Once again, nuclear phenomena are damn near magical.

[0]: [http://www.bris.ac.uk/earthsciences/people/cherry-l-
lewis/in...](http://www.bris.ac.uk/earthsciences/people/cherry-l-
lewis/index.html) . It's a solid department (though I'm biased - I used to
study there). They're totally immersed in all things earth science. Rarely
seen so much enthusiasm.

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srean
A conundrum that would tickle my (geologist) dad no end was that some of the
earlier estimates of the age of the universe were lower than some of the older
rocks found on the earth.

The article mentions red-shift of galaxies, it allows us to estimate their
speed. One of the older scientific estimates of the age of the universe was
based on "reverse" extrapolating those values.

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coldcode
Science history is among my favorite topics. Today we take it for granted how
much we know about things. Imagine being in a time when we knew virtually
nothing and still having the imagination to figure it out.

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xefer
For anyone looking for a bit more detail I would highly recommend:

"Ancient Earth, Ancient Skies"[1] by G. Brent Dalrymple

which is a distillation of the author’s earlier, more scholarly work:

"The Age of the Earth"[2]

if you're looking for a _lot_ more detail.

[1] [http://amazon.com/o/asin/0804749337](http://amazon.com/o/asin/0804749337)

[2] [http://amazon.com/o/asin/0804723311](http://amazon.com/o/asin/0804723311)

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elyase
This is how it works:

 _" Rock minerals naturally contain certain elements and not others. By the
process of radioactive decay of radioactive isotopes occurring in a rock,
exotic elements can be introduced over time. By measuring the concentration of
the stable end product of the decay, coupled with knowledge of the half life
and initial concentration of the decaying element, the age of the rock can be
calculated. Typical radioactive end products are argon from potassium-40 and
lead from uranium and thorium decay."_

\-- Wikipedia

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pdonis
This quote does leave out one crucial item, though (I don't know exactly which
Wikipedia page you are quoting from, so I don't know if it's brought up
elsewhere on the page, or on a page it links to): how do you know the initial
concentration of the decaying element? (This is often asked by creationists
trying to discredit radiometric dating techniques.) The answer is that, if you
make some additional measurements, you can figure it out from the data, as
explained in the Isochron Dating FAQ:

[http://www.talkorigins.org/faqs/isochron-
dating.html](http://www.talkorigins.org/faqs/isochron-dating.html)

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hawkharris
If you ever start to feel old, think in geologic time.

~~~
jofer
As a geologist, I assure you, it doesn't help.

The fact that your great-great-great grandparents are basically the same age
as you (penecontemporaneous with you, to use my favorite term) isn't exactly
comforting.

I'm kidding, of course :)

On the bright side, it's _really_ incredible how far civilization has come in
such a short time! Putting that in geologic perspective just makes it even
more impressive.

