Anders Peter Johnsen wrote:
> Og så lige til oversætterens kommentar: Jeg håber så sandelig ikke dét der
> skal forestilles at være "videnskabelig" argumentation for at
> Ungjordskreationismen, for mine alarmklokker lyste altså konsekvent gennem
> hele denne passage. Brugen af ord som "world class experts" (sjovt nok
> nævnes der ingen navne på disse "Verdensklasseeksperter"?) og så
> selvfølgelig lige den helt vidunderlige datering på "nøjagtig" 5680 år
> ("give or take" hele 2000 år!!!) tyder på at det bare ikke holder en meter
> rent videnskabeligt
>
> Helt centralt er nemlig denne ret tvivlsomme forestilling om at helium
> "sådan bare lige" siver ud af zirconer i massiv granit, selv i dybt
> grundfjeld, fordi heliumatomer er så relativt små. Opfatter man i ramme
> alvor disse heliumatomer mon som en slags "små fisk i et meget stortmasket
> atomnet"?
>
> Spørg evt. selv folk i dk. videnskab om den holder, for det lugter altså
> stærkt af at være dybt pseudovidenskabelig argumentation, der er konstrueret
> for at snyde autoritetstro lægmænd på nøjagtig samme måde som når Colgate i
> ramme alvor hævder at "fluortandpasta (men ikke nødvendigvis deres egen!)
> anbefales af førende tandlæger" i deres reklamer.
>
Uddraget er fra en meddelelse fra RATE gruppen som er en del af ICR -
Institute for Creation Research, en ungjordskreatiinistisk gruppe.
Her er en kommentar til en af udtalelserne fra RATE fra en af de
forskere de refererer
http://groups.google.dk/groups?q=icr+helium&hl=da&lr=&ie=UTF-8&safe=off&selm=86b7ec04.0210161541.6d34fa9%40posting.google.com&rnum=4
"Taking the approximate diffusion parameters for He diffusion in zircon
from our experiments, one would predict that zircon would retain 90%
of
its He over 10 myr if it were held at about 165 oC (would retain more
if
held at lower T), or over 1.5 byr if it were held at about 100-120 oC
(more if held at lower T). The only requirement for retaining most of
the
internally generated He over geologic timescales is that the
temperature
is lower than approximately 120-170 oC. This simply means that zircons
in
the upper ~7-9 km of the earth's crust (where temperatures are
typically
below about 175 oC) will have retained most of their He since the time
that they were above ~175 oC. There are many, many places where
erosion
and tectonic rates are slow enough that the upper crust remains this
cool
over tens to hundreds of millions of years, and sometimes billions of
years. So there is no problem. Zircon can retain He in its crystal
lattice
for timescales on the order of 10^7-10^9 years or longer, given
temperatures below about 120-170 oC. The only possible complication to
this is if zircon becomes radiation damaged because of high U-contents
and
extremely old age. In this case, He diffusivity decreases, but the
bulk He
diffusivity is still a function of temperature and time, and one can
apply
the same sorts of considerations as above, and you don't need to have
temperatures be too cold to still keep most of the He. I suspect that
the"
/Søren