[meteorite-list] F.A. Paneth - Radioactive Decay Processes and theAge of Meteorites

Sun Mar 22 05:57:58 EDT 2015

Guys,

Paneth is writing this in 1928 
because that is when George Gamov 
worked out the quantum mechanics 
of radioactive decay, particularly 
of the uranium and thorium series.
Paneth is merely appreciating the 
possibilitie.

There are dating possibilities 
because, while all the radioactive 
decay serieses end in good old 
long-lived lead, lead has several
isotopes (same atomic number; 
different atomic weights caused 
by hitch-hiking neutrons).

This is called lead-lead dating. 
However, measuring the exact 
abundances of lead atoms by 
isotope is tricky. You need to 
measure very long-lived elements 
if you're going date something as 
old as the Earth, but the longer 
the half-life of an element is, the 
more difficult it is to measure!

This was first done by geochemist 
C. C. Patterson (and George Tilton).
Cleverly, he measured the lead-
lead ratios in meteorites AND in 
ocean bottom sediment (which 
would contain a samples of lead 
eroded out of all the Earth's 
surface for hundreds of millions 
of years.

Bingo! Both extraterrestrial lead 
ages and terrestrial lead ages were 
essentially the same for the formation 
date of the solar system and the Earth:  
4.55 +/- 0.070  10^9 years.

Here's his 1956 paper:
http://www.colorado.edu/geolsci/courses/GEOL5700-9/pdf/Fall07/Patterson.pdf

Measuring both values answered 
Paneth's question: "In our present 
state of ignorance of how they were 
formed, we must admit the possibility 
that there may be meteorites 
substantially older than the oldest 
strata on Earth..."

Jumping all the way back to George 
Gamov... He was not only a great 
physicist, but a very good popular 
science writer. A Russian, he managed 
to wiggle out of the Soviet Union and 
come to the U.S. only a little behind 
Einstein wiggling out of Germany 
(both in 1933).

In the 1930's, Gamov worked out the 
basics of neucleosynthesis in stars. 
In 1940, he wrote a book, "The Birth 
and Death of the Sun" on the process 
of element creation in an early hot 
universe and the evolution of stars. 
Today, this is called "The Big Bang 
Theory," although he never called it 
that. But he's it's Father of the Big 
Bang..

In 1952, Gamov was re-printed as a 
early news-stand paperback book 
(paperback books were a brand-new 
thing then), and I still have my 
63-year-old copy bought with my 
school lunch money. 

I'd buy two milks and save the rest 
of the lunch money for books, the 
same way I bought Arthur C. Clarke's 
first book "Interplanetary Flight" that 
same year. It was much more slimming, 
as it was a hard-bound book and had to 
be paid for in advance because it would 
have to be imported by boat from far-away 
England. (This is how to be a complete 
geek yet not get fat.)

In Gamov, writing in 1940, I learned 
(because measuring the half-life of lead 
isotopes was so hard, hence imprecise) 
that the crust of the Earth was 1.6 
billion years old and that the planet 
and the solar system could not be 
much more than 2 billion years old.

By 1955, when Life magazine published 
their famous "The World We Live In" 
book (still worth looking over, BTW), 
they described the dating of the age of 
the Earth and Sun as "never less than 
2 billion and never more than four or 
five billion years." I guess the long 
half-lives of the lead isotopes was in 
the wind or they'd heard about C. C. 
Patterson's as-yet unpublished work.

He published the next year, and in 
the 60 years since, there has been no 
contradictory evidence found for that 
dating. Geochemists can get a good 
fight going by suggesting shifting the 
date by 10 or 20 million years.

Evidence converges on Patterson date:
the Earth's oldest "rock," the tiny Jack 
Hills zircon is 4.404 +/- 0.008 x 10^9 
years old. And the lunar sample, the 
"Genesis Rock," dates to 4.460 x 10^9 
years.
http://www.psrd.hawaii.edu/April04/lunarAnorthosites.html

Evidence from two worlds...

Sterling Webb
---------------------------------------------------
-----Original Message-----
From: Meteorite-list [mailto:meteorite-list-bounces at meteoritecentral.com] On
Behalf Of Galactic Stone & Ironworks via Meteorite-list
Sent: Saturday, March 21, 2015 9:14 PM
To: rickmont at earthlink.net
Cc: Meteorite List
Subject: Re: [meteorite-list] F.A. Paneth - Radioactive Decay Processes and
theAge of Meteorites

Hi Rick and List,

Our knowledge of meteorites has changed a great deal since 1928.  :)

Best regards,

MikeG
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On 3/21/15, rickmont at earthlink.net <rickmont at earthlink.net> wrote:
> Notwithstanding any uncalculated (our inability to do so) time anomaly,
> bringing in the ol' Relativity question.   To what degree is this a valid
> consideration?
>
> -----Original Message-----
> From: Galactic Stone & Ironworks via Meteorite-list
> Sent: Saturday, March 21, 2015 4:01 PM
> To: Meteorite List
> Subject: [meteorite-list] F.A. Paneth - Radioactive Decay Processes 
> and theAge of Meteorites
>
> "As is well known, the most exact way of determining the ages of rocks 
> depends upon the regularity of radioactive decay processes. Obviously, 
> the same method can be applied to meteorites... In our present state 
> of ignorance of how they were formed, we must admit the possibility 
> that there may be meteorites substantially older than the oldest 
> strata on Earth..."
>
> ---> F.A. Paneth (1928)
>
> Uber den Helium Gehalt und das Alter von Meteoriten, Z.Elektrochem, 
> Vol. 34, pp. 645-652
>
>
> --
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