I know that you wrote this in jest but my e-mail to Allen was not intended
that way. Arguments can be made that some supposedly closed systems are not
as closed as one had hoped and, therefore, bias one or other age dating
method. As far as I know, these arguments cannot be applied to Oklo for the
simple fact that present-day 235/238U ratios cannot sustain a chain
reaction, no matter how high the [U], unless the fast neutrons are moderated
by a material that has a low neutron capture cross section, such as D2O.
Yes, if half lives are not constant but were shorter in the past, it is
conceivable that the 235/238U ratio would have been sufficiently high 6000
years ago, but this would fly in the face of physics. If YEC hold to half
lives that increase with time, they would need to square that with physics
and apply it to all geochronological data.
Still, I'm open to a consistent alternative interpretation of the Oklo
From: D. F. Siemens, Jr. [mailto:email@example.com]
Sent: Thursday August 23, 2001 11:19 PM
Cc: firstname.lastname@example.org; email@example.com
Subject: Re: Response to Why YEC posting
But Chuck, don't you understand that the half-lives are variable on YEC
"principles"? Consequently, your claims do not hold.
On Thu, 23 Aug 2001 23:46:28 -0400 "Vandergraaf, Chuck"
> Thanks for the reference. Trouble is, I don't have ready access to
> To me, the Oklo phenomenon can only be explained if one assumes that
> earth much older than YEC's would claim. Briefly, a nuclear chain
> can only be sustained if 1)the 235/238U is higher than at present
> compared to the current <0.8%) or 2) a moderator such as D2O is
> present. The
> U deposit at Oklo shows unmistakable signs of fission: rare earth
> products show an isotopic signature closer to that of fission
> there is eveidence of 99Tc (which is only produced in the fissioning
> process), and the 235U is depleted considerably, to values as low as
> If the fission process did take place, the 235/238U must have been
> higher than present, in the order of 2% and that can only have been
> the case
> ~10^9 years ago because the half life of 235U is shorter than that
> of 238U.
> The Cigar Lake U deposit is younger and never had a sufficiently
> 235/238U ratio.
> This, to me, clearly swings the evidence to an old earth but, as a
> scientist, my mind is open for alternative interpretations.
> -----Original Message-----
> From: Allen Roy [mailto:firstname.lastname@example.org]
> Sent: Thursday August 23, 2001 8:18 PM
> To: Vandergraaf, Chuck
> Subject: Re: Response to Why YEC posting
> I personally don't know much about the Oklo reactor, however I found
> article by a YEC on the topic.
> "Oklo Uranium Reactor Examined From a Creationist's Viewpoint"
> appears in the Creation Research Society Quarterly Vol.19, No.1
> (June, 1982)
> pgs32-35 by Eugene Chaffin
> ----- Original Message -----
> From: Vandergraaf, Chuck <email@example.com>
> To: 'Allen Roy' <firstname.lastname@example.org>
> Cc: <email@example.com>
> Sent: Wednesday, August 22, 2001 12:34 PM
> Subject: RE: Response to Why YEC posting
> Please explain, using a "young earth model," how natural fission
> e.g., @ Oklo, Gabon, could have operated while other U deposits with
> [U], e.g., Cigar Lake, did not.
> Chuck Vandergraaf
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