Re: Kirk's comment

On Jul 12, 5:45 pm, "Dr.GH" <garyh...@xxxxxxxxxxxxx> wrote:
On Jul 12, 5:43 am, Robert Carnegie <rja.carne...@xxxxxxxxxx> wrote:





Dr.GH wrote:
On Jul 11, 5:48�am, Robert Carnegie <rja.carne...@xxxxxxxxxx> wrote:
I'm uncomfortable with having C14 that was in a sample when you dug it
out of the ground classified as "contamination" - I presume this is
where nitrogen in coal receives radiation and converts to carbon-14.
But I understand that it's distinct from carbon-14 present millions of
years ago when the coal was laid down. �(Although the nitrogen atom
might have been carbon-14 previously.) �So, in a way, radioactivity is
acting on the coal and contaminating it.

I haven't found yet whether this categorisation is in the article
itself, which describes the situation at greater length.

The clearest example is bone. As Bertsche points out, anomalous C14 is
found in the mineral carbonate of bone, but not in the protein
collagen from the same bone. The bone calcite is easily replaced by
calcium carbonate disolved in groundwater. This replacement carbonate
is contamination.

What I could do is add one or two links in a side-bar to some online
tutorials in C14 dating. For example;

Radiocarbon Web
http://www.c14dating.com/

Arizona Accelerator Mass Spectrometry (AMS) Laboratory
http://www.physics.arizona.edu/ams/education/theory.htm

Other side-bar links will go to the RATE group's web page, etc.

I'd forgotten about bone - and I thought that wasn't amongst the RATE
challenges against radiocarbon dating.  That's a more clear-cut case,
perhaps, where radioactive material is imported into the relic or
exported from it.  And it seems that particular one is solved, in the
sense of "Scientists know what to do about this."

I seem not to be winning in arguing for a specific verbal distinction
between influences that occur before and after scientists get their
hands on the material, the latter being possibly avoidable - if it
mattered: for real scientific inquiry, as opposed to stupid RATE
games, the present state of the art is good enough.

The terms "contamination" and "background" are used somewhat
interchangeably in the literature.  You will frequently see the term
"in-situ contamination", but this is often used quite loosely to
refer to ANY contamination of the sample before it reaches the
testing lab (i.e. true in-situ contamination, contamination due to
sample collection, or contamination due to storage).  Sample
contamination is a crucial issue, and has been stressed by Beukens
and others.  Samples can be contaminated by either carbon addition
or
carbon exchange (e.g. from groundwater, atmosphere, biological
activity) or from radiocarbon generation (due to nearby neutron
generation from radioactive decay or due to cosmic rays).

There is a slight nuance between "contamination" and "background",
I  suppose.  "Background" implies a quasi-constant, quasi-repeatable
effect which can often be corrected for to some level.
"Contamination" implies more of a random, unpredictable effect which
cannot be corrected for.  But both terms refer to the same types of
contributions, and are used somewhat interchangeably in the
literature, so I have not tried to make this distinction in my
paper--
it is a minor point which would add confusion.

I think I have to be persuaded by that argument. I suppose too that
human contamination of samples outside the context of experiment, such
as the use of either "organic" or synthesised fertilisers, and also
letting off A-Bombs and H-Bombs, could interfere with results,
anywhere in the world. And that if a clear distinction /could/ be
made, scientists every day are not doing so, so it would be like the
fabled action of King Canute.

Is it correct to say that Baumgardner, or any other researcher, would
be handed numerical readings and error bar allowances for his
laboratory samples and left to interpret that for himself? I mean,
the laboratory wouldn't be telling him, "It doesn't say zero, but it /
means/ zero" - for the diamonds - except by such technical terms? It
would be up to him?

This seems to me a weakness - but only in allowing incompetent or
deliberate misinterpretation. It isn't your job to hold the
customer's hand and lead them through the whole process.

If my understanding is also correct that radiocarbon dates are still
expressed in the unit of "ybp" i.e. "years before present" which does /
not/ correspond to "calendar years" throughout the scale because -
presumably - the proportion of carbon-14 in the environment has
changed... then that's unfortunate too. Particularly so if you have
that /and/ the previous thing, so that the laboratory publishes a
"year" date for the coal, etc.

.

Relevant Pages

  • Re: Kirks comment
    ... out of the ground classified as "contamination" - I presume this is ... where nitrogen in coal receives radiation and converts to carbon-14. ... calcium carbonate disolved in groundwater. ... it is not the responsibility of the lab. ...
    (talk.origins)
  • Kirks comment
    ... out of the ground classified as "contamination" - I presume this is ... where nitrogen in coal receives radiation and converts to carbon-14. ... collagen from the same bone. ... calcium carbonate disolved in groundwater. ...
    (talk.origins)
  • Re: Second reading of "RATEs Radiocarbon: Intrinsic o
    ... out of the ground classified as "contamination" - I presume this is ... where nitrogen in coal receives radiation and converts to carbon-14. ... The clearest example is bone. ... between influences that occur before and after scientists get their ...
    (talk.origins)
  • Re: Second reading of "RATEs Radiocarbon: Intrinsic o
    ... out of the ground classified as "contamination" - I presume this is ... where nitrogen in coal receives radiation and converts to carbon-14. ... point of view of a laboratory guy. ... in situ contamination cannot generally provide an accurate date.</ ...
    (talk.origins)
  • Re: Key "Stardust" spacecraft discovery may have been contamination (Forwarded)
    ... Key "Stardust" spacecraft discovery may have been contamination ... One of the biggest scientific surprises from last year's "Stardust" space ... Martinez-Frias and colleagues point out that scientists were surprised to ... Osbornite forms only at ultra-hot ...
    (sci.astro)