I'll give some quick answers here. If they aren't sufficient, then ask some more.
quote:So the question is, why can we know the half life of this method in such a short period of time, and not able to use it on anything under the age of 100kya?
This is because the half-life of a long lived element isn't measured by waiting for half of it to decay away. One can calculate the half-life simply by calculating the rate at which it decays, that is, by counting how many atoms decay in a second. Of course this is (more or less) the number of clicks you hear on the geiger counter in a second.
I can go through the math if you want, but this is the basic answer.
quote:I have read else where but this link will suffice. It says that Potasium-argon does not work for recent dates. I wonder, why not?
This is because one must measure the amount of Argon-40, which is produced by the decay of Potassium-40, that is present and compare it to the amount of Potassium-40. This will determine what fraction of the original K40 has decayed, and will determine how old the sample is.
Well, if the sample is too recent, then not very much K40 has decayed at all. So there is only going to be a very, very minute amount of Ar40, perhaps so minute that our instruments cannot even measure it. Or so minute that the inaccuracies in measurement will be large compared to the actual amounts. In fact, minute contamination -- Ar40 left in the instrument from the last sample dated -- could very well make it seem like the amount present is much more than in actuality, and so the sample will seem "younger" than it really is.
Of course, for a truly old sample the amount of Ar40 present will be large enough that errors like a small amount of contamination (which should still be avoided if possible) will only be a tiny fraction of what is actually present.
The problem is that many sensitive instruments will rarely read "0" even if the amount is "0". All measurements contain some small error -- however, if the real signal itself is small, then this error will be a large fraction of the value returned by the instrument.
quote:If radiocarbon dating is only useful for a maximum date of 100,000 why is it that when dating anything older we would get "back nonsense numbers"?
This is because, as Iname pointed out, C14 dating is done opposite the way K/Ar dating is. Here we measure the amount of C14 that is present. However, C14 decays very quickly, so very soon only a very, very small amount is left. The amount left is so small that our instruments cannot measure it very accurately, or even at all. Things like background radiation or contamination from a previous sample will make it seem like some C14 is present, and so, again, it may make it appear that the sample is younger than it really is.
quote:from a creationist perspective, why not date objects subjected to the carbon cycle at some point in time and measure their age using radiocarbon?
Well, creationists believe that the earth and all that is contained therein is only about 6000 years old or so. What are they going to do with C14 dates that indicate an artifact is 10,000, 20,000, or even 75,000 years old?
On pages 171-174 they discuss why all but one potassium/argon date for the Rusinga Island bioites was discarded.
What was their discussion? It seems a bit unfair to blame them for deciding that some of the dates were unreliabe without hearing their side of the story.
Paul notes: "It is interesting to speculate what would happen if an article in chemistry or medicine were submitted with perhaps 1/6 of the data reported."
But according to the article they did report the dates.
Now why in the world would they publish the fact that they discarded the dates, for the entire world to read, if there was something fishy going on?
Evernden et al. can be accessed online, although I don't want to pay to see it. If anyone has access to a university library, they can probably read the article themselves. All I can get is the abstract:
Potassium-argon ages of sanidines, biotites, and basalts are found to be in essential agreement with time-sequential dating of Tertiary land mammals. A detailed time scale of the Tertiary based on an age breakdown is given.
Now, why would they say this in the abstract if someone reading the article could tell that this was not true? In fact, if they were trying to hide something, if they were trying to dupe someone, why would they say anything at all?
Something doesn't seem right in this accusation. If Evernden et al. were frauds, they seem to be incompetent frauds. How would their findings be published if they were so obviously fraudulent?
quote:The website I got it from did not mention anything about conspiracy, that is something you guys have placed inside creationists mouths. Stop doing that.
If you would notice, the post to which you replied was a response to CDT, who was implying that there is a conscious effort to hide inconvenient dates.
quote:Remember that the 5/6th of samples that were disregarded passed the test for dating when they were in the field collecting them, it was after they got the dates that they threw them out because they were way off, so instead of saying "why" they throw them out because it does not agree with the "factual" dating paradigm.
How do you know that they did not say why they discarded the dates? Have you read the paper yet? It seems a bit crass to accuse these people of something untoward like discarding inconvenient data without at least presenting their arguments for why they did so.
I have submitted an interlibrary loan request for this paper. I should be getting a copy within a week. Maybe we can determine whether their decision was unreasonable.
quote:Here is why radioactive dating could give wrong dates....
Yes, and the sources show that K/Ar dating may be inappropriate for pillow lavas. Pillow lavas are pretty easy to identify. So if the sample is from a pillow lava, one would know to not date it using the K/Ar method, or at least be very suspicious of the date if K/Ar is used.
So, if we know what that some samples are problematic, and if the problematic techniques are avoided, what exactly is the problem?
Wow. That was fast. I got my free PDF copy of Evernden et al. by email this morning. I think I'm gonna like interlibrary loan!
Creation moonbat website claimed: On pages 171-174 they discuss why all but one potassium/argon date for the Rusinga Island bioites was discarded. Yet they use biotite in an uncritical manor in other areas where the dates they obtained matched their expectations.
I will be quoting directly form Evernden et al.; I am assuming that the amount quoted will lie within fair use standards.
Evernden et al., p. 172: The potassium-argon results obtained on biotite samplescollected from the tuffaceous sediments of Rusinga Island are highly variable.
In other words, rather than hiding a problem, they are admitting it to the world that obtaining reliable dates is difficult.
Evernden et al., p. 172: These detrital sediments lie upon a Precambrian surface and may be expected to contain significant fractions of Precambrian biotite. [Bolding added.]
On other words, the problem is contamination with far older material. If YEC were true, the Precambrian material would not be very old, and so the contamination would not have led to older dates. It is because the Precambrian material is so old that this problem is occurring.
Evernden et al., p. 172: If such occurs, widely variable K-A dates may result with the minimum age yielding the best estimate of the age of the deposits. If the sample yielding the the minimum age has characteristics that reduce the possiblilty of contamination, we can accept the figure obtained from it as a close estimate of the true age of the deposit. [Bolding is added.]
In other words, it's not a question of choosing the one date that "matches expectations". The best date will be the youngest, and there is no guarantee that this one is going to match "expectations".
Evernden et al., p. 172, 174: The sample used for KA 336 was composed of large (1/2" diameter) euhedral biotite books collected from tuffaceous sediments at the site R 107 in the Kiahera Series. This site is stratigraphically below most fossil-vertebrate localities on Rusinga Island. All other determinations were made on fine-grained biotite concentrated from tuffaceous sediments, all of which might have appreciable contaminating components. The obtained argon-potassium "ages" indicate high contamination: KA 656 -- 22.2 million years, KA 800 -- 42.0 million years, KA 801 -- 167 million years, KA 802 -- 107 million years. Thus our best estimate for the age of the deposits on Rusinga Island is that of KA 336, that is, 15.3 ± 1.5 × 106 years, an age equivalent to the Barstovian of North America. The fossil evidence from these deposits does not appear to contradict this age. [Bolding is added.]
In other words, we actually see a large spread of ages. The "best" age was not chosen, rather, it was determined that the "best" age would be the youngest, and it still might have been older that the fossil evidence would have indicated.
The youngest sample was examined, it was determined that contamination from the un-YEC ancient Precambrian was less likely, and, indeed, the it was close to the age suggested by the fossil evidence, ages that were determined elsewhere by more reliable means.
So, everything seems on the up and up. I certainly see no signs that problems are being hidden or brushed under the rug. Their procedure is explained, the data is given, and anyone anywhere can look at this paper and make up their own minds as to the reasoning of the authors.
Isn't this all developed based on a uniformitarian philosophy?
No. It is based on a uniformitarian assumption that can be (and has been) verified by the usual scientific methods.
I'm sure some admin or mod will say i'm off topic, and to side step the question. GIVE ME LIBERTY OR GIVE ME A NEW FORUM NAME!
like "Evolution Think Tank", or "Evolution Circle Jerk" or perhaps "The Average Person Just Doesn't Grasp The Complexity or Understand The True Logical Behind Our Precious Evolution Fact/Lie" or "Were Obviously the Highest Evolved Unlike Those Niggers."
This repitition is going to get tedious. Are you a troll? It appears that your main purpose here is to disrupt things.
I've done everything the Bible says, even the stuff that contradicts the other stuff! -- Ned Flanders
Yes, your posts basically are. It will be interesting to see whether you are capable of making an argument based on facts and logic, or whether disposable one-liners are all you have.
uniformitarianism has been verified?
Sure has. Every prediction made in geology, evolutionary biology, cosmology and the like is based on the assumption of the laws of physics and natural processes behaving as we understand them. So, tests of geologic, evolutionary, and cosmologic theories are tests of uniformitarianism. And so, every time a prediction is actually observed to be confirmed, the uniformitarian assumption is confirmed.
No, it's not a red herring. It is how the assumption of uniformitarianism is justified. When different independent methods give the same answers, either the assumptions are correct, or we are witnessing a remarkable set of coincidences. For some reason, creationists prefer to believe the world is filled with remarkable, unexplainable coincidences.
The method of dating isn't in question.
Huh? What are you talking about? You and your link are questioning this method of dating. You are confused.
The fact that airplanes 50 years ago would date to millions of years is the question.
Huh? Who dated the airplanes? Not even your link claimed that anyone dated the airplanes. Your link just talks about the planes being buried under a lot of ice.
...explain to me how antartica isn't an active glacier.
Because they can actually observe the movement of the ice.
And in the last sentence its uniformitarianism all over again.
Sure. Because the assumption of uniformitarianism matches with actual observations.
Here is one abstract about volcanic ash found in an ice core in Greenland. The minerology of the ash is very similar to ash taken from a sediment core in the Atlantic. If the uniformitarian assumption is correct, then the two dates of these ash deposits should match. There's no other reason why these two different dating methods should give the same ages.
And the ages do match up. Just as the uniformitarian assumption predicts. To a creationist, this is another amazing coincidence among a huge number of coincidences that a creationist must accept. To someone with a little bit of sense, though, this is not surprising. One can count annual layers in the ice. One can use oxygen isotope dating to date layers in ocean sediment cores. And, seeing how these two methods agree with each other (and with examples in other dating methods), it appears that our confidence in our assumptions are justified.
Edited by Chiroptera, : No reason given.
I've done everything the Bible says, even the stuff that contradicts the other stuff! -- Ned Flanders