Douglas J. Bender

I will admit that I was mistaken as to the actual error in the "isochron dating" reasoning, but in all honesty I would say that my error was due to ardipithecus' lack of a clear explanation about determining D[N]/Di and P[N]/Di (all he said was that samples would need to be taken from various places on the rock, which isn't a truly "enlightening" explanation as to both why one would do so and how it would result in allowing one to find the time t and D[Orig]).

However, I am wondering what physical or chemical processes would explain why the molten lava would result in a non-homogenous distribution of the parent (P), but not of D[i] in relation to D. Any clarifications or explanations of this, for a chemistry and geology layperson?


In Christ,

Douglas

[ May 12, 2002: Message edited by: Douglas J. Bender ]</p>

Valentine Pontifex

The reason why D/Di starts as constant while P/Di does not comes to the fact that D and Di are the same element (but different isotope) while P and Di are different elements.

Strontium and rubidium (the daughter and parent in Rb-Sr isochron dating) act in very different ways. They are on different columns on the periodic chart and thus are very different chemically. Rb melts at 38.89 C, boils at 688 C, and has a specific gravity of 1.532. Strontium has a melting point of 769 C, a boiling point of 1384 C. and a specific gravity of 2.54. (Source is an old CRC.)

Imagine now that the lava is become solid as it cools. One would expect that Sr would more easily turn to solid. Also there are other elements in the lava that interact with Sr and Rb differently. Thus it would be almost impossible to form a rock that had an absolutely uniform Rb/Sr ratio.

But the various isotopes of Sr all act in the same way. Hense the ratio of one isotope of Sr to another Sr will almost certainly be constant as the rock forms. It will stay constant until different spots on the rock gain strontium-87 from the radioactive decay. Since the gain comes from rubidium's decay it not related amount of strontium already present. Thus it initially constant strontium isotopic ratios will cease to be constant.

Principia

[ May 12, 2002: Message edited by: Scientiae ]</p>

Ragnarok

Nice summary SC. This is definitely one that can be added to the "A" list of Bender's fuck ups. Let's review

1) &lt;laughter type="hysterical"&gt; The Biblical Equations&lt;/laughter&gt;

2) Doug knows when the world will end. Some time in 2003 I believe.

3) David Blaine "street magician" does real magick. I always thought that goatee of his was a little Satanic.

4) The Demon Haunted Rooftop.

5) The Isochron cock-up.

Feel free to add to the list people.


[ May 12, 2002: Message edited by: Ragnarok ]</p>

Coragyps

From LV's most recent post:
For example, strontium carbonate and strontium sulfate are almost totally insoluble in water, where these rubidium salts are extremely soluble. These particular compounds are not that likely in igneous rocks, but the principle is widely applicable: rubidium has a +1 charge and a larger ionic radius than the +2 charged strontium. They just won't fit in the same places.
I just finished Dalrymple's The Age of the Earth (<a href="http://www.amazon.com/exec/obidos/ASIN/0804723311/qid=1021258326/sr=12-3/104-3109700-2436711" target="_blank">here, </a>or at the library) and found it very helpful in knowing how dating methods work: sort of a "little sip from a firehose" if you don't really want to know. He presents hundreds of dates, with three or four different isotope pairs on many rocks, and discusses the assumptions used, probable errors, etc., in detail.

Douglas J. Bender

My "admission" was basically an admission that I was in error, but that that was because of an inadequate description by ardipithecus of his reasoning and methods. Of course, I was in error about some things regarding his reasoning prior to this (for example, thinking that Di could be ignored, etcetera). I never claimed to be perfect, mind you. And I never boasted (note my use of the term, "boast") that my abilities were better than anyone's here, although I do believe they are better than most, generally.

In Christ,

Douglas

[ May 12, 2002: Message edited by: Douglas J. Bender ]</p>

Douglas J. Bender

I don't see why the "thus" statement necessarily follows from the preceding statements. (Of course, I know basically nothing about chemistry or geology - I'm just offering my opinion as I understand things as they have so far been explained.) One of the assumptions necessary for the "isochron dating" method is that (D/Di) was the same throughout the rock when it formed - I guess I'm still not convinced of the validity of this assumption. I understand the part about P being significantly different than D and Di, but if part of the rock could have a higher concentration of P than another part as it was forming, then I don't see why the same could not be the case for D and Di, and that their concentrations at various places might not be inversely related, just because of the (I'm assuming) chaotic dynamics of the formation of the lava flow and the rock.

Anyway, it looks like I'd probably need a hefty education in geology and chemistry (compared to what I have) before I could make a sound judgment about "isochron dating". It happens, sometimes.


In Christ,

Douglas

[ May 12, 2002: Message edited by: Douglas J. Bender ]</p>

MadMordigan

<img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

Douglas J. Bender

The Biblical Equations are quite valid. I assume your "hysterical" laughter is that of someone who has been shown that their worldview is a myth.

I've NEVER claimed to "know" any of this, Rag - I've claimed that I believe there is very strong reason to believe that some time in 2003 the 7 year Tribulation would begin. And the "end of the world" would come 7 years after the Tribulation began. Those reasons are quite convincing, in my opinion.

I've never said that David Blaine does "real magic(k)". I've said that IF there was no trick photography involved (including editing [if this is not considered part of "trick photography"]), THEN David Blaine must be doing some "real magic(k)". There's a difference.

No one's ever offered a reasonable, "naturalistic" explanation for that experience. The best anyone could come up with was "squirrels", or "You and your two friends were all delusional", or "You're just plain lying". Not terribly convincing "rebuttals" or explanations. ("Squirrels"... )

Not one of my proudest moments, but as I've said, I believe my mistake was more the result of a lack of a clear explanation of the reasoning involved. For the most part. In any case, I'm still not convinced that D/Di would be the same throughout a rock when it initially forms. (I mean, if it is not assumed that D itself is homogenous throughout the rock, but varies from place to place, then what would account for that variation? If P varies from place to place in the rock, why couldn't D...? Anyway, questions I most likely need quite a bit more chemistry and geology in order to understand and answer.


In Christ,

Douglas

Vorkosigan

Doug, if you know nothing of geology or chemistry, why did you think you had found an elementary error? Why is it, without background knowledge, you think you are better than the great run of people? Out of curiousity, what did you study in college?

You know, when I warned you that you would wind up with egg on your face, I didn't know anything about geology or chemistry either. I did know about Doug Bender, though. Note for the future: frame error claims as sincere questions. That way you will reveal error, without risking loss of face for self or other discussants.

However, I am sincerely grateful for your admission of error, however churlish and grudging it was.

Vorkosigan