How accurate is radiometric dating?

@farmerman,

What about radiodating igneous rocks of known age? Have you done any of these?

@Blue Grass 6,

I havent but colleagues have. We dont do K/Ar on stuff we can see happen or has happened in the century before.I usually get a newspaper. Ive had my favorite contract labs do C14,C12/13/14 for percolating water movement in ore bodies . Everything else Ive had my labs do includes tree rings, laser ablation tree rings,Flouride dating,,Exposure dating[3He,36 Cl,10Be etc, Thermoluminescence,OSL, and electron resonance) are not really radiometric dating techniques in the strictest sense.

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@Blue Grass 6,

Quote:

What about radiodating igneous rocks of known age? Have you done any of these?

Science isnt out to prove Creationists wrong by doing what we know the answers to be, were fairly economical about that.
I know that, of all the samples the Creationists have sent to labs to do rad dating by mthods that dont comply (like K//Ar under 100 K years, or Ar/Ar under 10 K yers). Its easier to contaminate such samples and introduce daughter isotopes from the surroundings (Zirons are a very common heavy mineral in the environment and they will contain several daughter isotopes of several radionuclides that could **** up our analyses by contamination

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@farmerman,

Won't older rocks be even more susceptible to contamination than young ones? If young rocks are easily contaminated, how does being older make them less contaminated?

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@Blue Grass 6,

its all equilibrium and contamination. Newer rocks are easily contaminated by stray isotopes of "daughter nukes" and "resetting errors" This would give a false "older calendar date) to the new rock.

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@farmerman,

Indeed, the new rock has a false older calendar date, but as that rock grows older (say after a million years), doesn't that false "older calendar date" still increase by the same amount (a million years)?

If you've already got stray daughter isotopes in the new rocks, don't those daughter isotopes just increase with time?

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@Blue Grass 6,

true, but we can fairly easily do a cross check at computing what the ratio of POTASSIUMs actually are in the sample. (K has 3 isotopes present but only one is radioactive). Creationists have never spent any time doing the actual QA to see whether the K is within a realistic ratio defined by the mineral chemistry..

Dont get me wrong, there are several ahortcomings in K dating including the fact that, due to branching decay paths, we aint quite certain about the decay constant. Also the technique relies more n ratios than other means and it can cause problems of introduced isotopes. eve gone to rely more on 40K/39Ar than 40K/40Ar. (and there are severl means that look at daughter Calcium ratios).

Hence, e dont like to use the technique in really young stuff mANY ARCHEOLOGICAL DATA MAY BE CRAPPY).
.
But, all in all, we use it knowing the shortcomings.
If you could follow the math, It would be easy to see where several errors can get introduced and, where we have to be careful in lab cleanups and multiple decay pathways.

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@farmerman,

'we ain't quite certain'.

All I was looking for.
namaste

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@farmerman,

If you can cross check using the ratio of K isotopes, then surely it wouldn't matter whether the sample was young or old. The mathematics would be the same. If the cross check works on old samples, then surely it also works on young samples. Why should it not?

As for creationists, if they're sending in the samples to dedicated labs for dating, why do they need to do the QA and check for the K ratio? Isn't that up to the labs to factor that in to their dating results? They are the ones doing the chemical analysis and date calculations.

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@Blue Grass 6,

they are sending samples unverified and without most field documentation. The labs cant work in a vacuum.

In K dating the crosschecking prevents the sample from appearing too old. Doing QA on other allows us to do several different dating techniques and besides, good field processes usually have the techs submit duplicates.

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@Blue Grass 6,

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The mathematics would be the same

not really, you can easily look it up on a number of websites. We have all kinds of checks for "parentless" Ar or Ca. Thats where Creationists practice their fraud .Eadiometric methods are strait forward but there are several areas of concern that, if ignored or purposely omitted , can make dates that dont provide any factual evidence.

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@farmerman,

So then why can't you also check for "parentless" Ar or Ca in young rocks?

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@Blue Grass 6,

think about it. Geologists arent idiots with spending research money(and we always demand that cross checking things like "lambda" and methods is usually done by our labs for increasing their own accuracy and sensitivity)

Remember that the "lambda value" (decay constants) are reciprocals of half -life and these are always being checkd and cross checked.

C14-shouldnt be used for anything over say 65 K (WHY?-cause C14 disappears from the sample and any C14 reported woul make the sample appear YOUNGER than it is.--Creationists futz with this by reporting out C14 values in "word salads" hoping their true believers wouldnt be smart enough to question the science.

K/Ar -i a ratio between the parent (K) and the daughter (Ar) (or Ca) and and any increase in Ar would make it appear that the sample was OLDER than it is.
Several other methods have built in trickster points so what I find really annoying is that, instead of really explaining the science to thir audiences, the Creationists actually COUNT ON their audience being not too bright in the subject so they can buffalo them with what sounds like science but aint. Thats criminal fraud in my book

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@farmerman,

Just want to say "Amen! Farmerman".

You are answering this nonsense with both expertise and patience. I don't think I could do it.

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@maxdancona,

Im not sure where hes going. I just get all defensive when someone asks general questions that seeem to be linked to what creationists say about radiometric dating.

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@farmerman,

I think you know this... I was a "bible-believing" Christian once. Then I got a science degree. I know both sides of this coin pretty well.

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@farmerman,

If you're worried about extraneous C14 being reported in specimens over 65K, shouldn't you also be worried about extraneous C14 in specimens under 65K too? Either way, the specimen is going to report younger than it actually is, so it's no longer accurate and reliable regardless of whether the sample is young or old.

Surely you can see that dating systems that can't self differentiate between what is young and what is old is problematic. If it can't self differentiate between these two simple aspects, what hope do we have of it actually determining even just ballpark figures for us? If young rocks date old, and also old rocks date old, then the system is clearly broken.

The lack of scrutinizing of dating systems with samples of known age further reveals how questionable these dates are. Without doing tests on samples of known age, how can you ever be sure of how accurate the results are to actual ages? Setting up rules like you shouldn't date objects less than 100K years makes dating samples of known age impossible.

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@Blue Grass 6,

Quote:

The lack of scrutinizing of dating systems with samples of known age further reveals how questionable these dates are. Without doing tests on samples of known age, how can you ever be sure of how accurate the results are to actual ages? Setting up rules like you shouldn't date objects less than 100K years makes dating samples of known age impossible.

This shows a fundamental lack of understanding of how science works. Part of a scientific education is mathematical modelling and error analysis. And, scientists use the tools to express, explain and test theories.

What you are saying about how "questionable these dates are" is simply wrong. We actually know how accurate these dates are, and can express the accuracy mathematically.

I am going to guess that you haven't taken any university level classes on error analysis.

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@maxdancona,

I was wondering when the shoe would be dropped. Ive gotta run some market lmbs to the auction. Ill be back later.

Methods selection is also a part of QA and overall accuracy analyses .

Ive always liked these summaries (this one was posted on Wiki)

Quote:

(ACCURACY AND PRECISION)

Precision is a description of random errors, a measure of statistical variability.

Accuracy has two definitions:

More commonly, it is a description of systematic errors, a measure of statistical bias; as these cause a difference between a result and a "true" value, ISO {5725} calls this trueness.
Alternatively, ISO defines accuracy as describing a combination of both types of observational error above (random and systematic), so high accuracy requires both high precision and high trueness.
In simplest terms, given a set of data points from repeated measurements of the same quantity, the set can be said to be precise if the values are close to each other, while the set can be said to be accurate if their average is close to the true value of the quantity being measured. The two concepts are independent of each other, so a particular set of data can be said to be either accurate, or precise, or both, or neither.

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@farmerman,

This is part of my thinking about scientific literacy. I don't think anyone can understand error analysis until they have actually taken classes and used the mathematics in a lab setting.

People don't realize how powerful the mathematics are until they have practical experience with the tools.

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How accurate is radiometric dating?

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