How, exactly, is dating done?

Yes. Isochron methods require multiple samples (typically 6 to 8 is a good number) from the same source. When these samples are measured and plotted on an appropriate graph, two things can happen:1. The points do not lie on a straight line and the test results in a failure to find an age.2. The points do lie on a straight line.There are three sub-cases of case 2:2A. The points also lie on a straight line on a different graph called a "mixing graph", and the test results in a failure to find an age because the isochron line is a result of mixing of two sources of different isotopic composition.2B. The points do not lie on a straight line on a mixing graph, and the slope of the isochron line is an indicator of the age of the samples and the Y-intercept of the isochron line is the ratio of parent-to-daugher at solidfication for all the samples. Note that the initial amount of daughter isotope is measured by the isochron technique, and therefore isochron methods are not affected by daughter product present at solidification.2C. The points do not lie on a straight line on a mixing graph, and we think we have a good age determination, but pure random chance made the seven or so points line up or the samples were formed by a complex mixing scheme of three or more sources with exceptionally unlikely isotopic makeups or some other very unlikely occurence.There may be a few case 2C's in the literature, but it's pretty obvious that very unlikely events don't happen over and over and over again, so most are 2B (and some 2A's are pblished as known mixing isochrons).Now, in reality, for various reasons the only isochron technique that is widely used today for determination of extremely precise ages (the question of approximate ages, within a few percent, having been settled long ago) is Argon-Argon, in which it is rare to actually draw an isochron diagram, but the methods that are used are equivalent to an isochron diagram (but more difficult to explain).There's a short basic discussion of all radioisotope techniques at Radiometric Dating: A Christian Perspective, and there's a fairly technical but readable explantion of isochron techniques at Isochron DatingNope, and nope. Don't worry, they're wrong.In isochron dating, the initial parent/daughter ratio is one of the results of the analysis.We've never found a rock that's 4.55 billion years old. We have rocks that are around 4 billion years old, and we've found zircon grains that are 4.4 billion years old. The 4.55 billion year age of the Earth is derived from Pb-Pb dating, an isochron method (and therefore not affected by initial daughter problems) that is a little too complex to explain here.Probably the most popular technique for age determination today is U-Pb concordia-discordia, which is not an isochron technique but is instead a simultanous application of two independent dating methods. This method is very widely applicable, the half-life of uranium is known to far greater precision than any other half-life (guess why), and it can even give a valid age if there has been "open system behavior" (e.g. loss of Pb to diffusiion or leaching and what-not).U-Pb dating requires that there be no significant daughter isotope at solidfiication, so it is used solely on minerals which strongly reject lead at solidification, usually zircons. It's physically impossible to solidify a zircon with enough lead to screw up U-Pb dating, unless there's also so little uranium that the dating wouldn't work anyway. The sexiest U-Pb dating is done essentially in situ in a Sensitive High-Resolution Ion MicroProbe, or SHRIMP (see Centre for Excellence in Mass Spectrometry). SHRIMP is so sensitive, and needs so small a sample size, that it can date sedimentary rocks by looking at the zenotime that forms between grains when the rock lithifies (see U-Pb SHRIMP Dating of Diagenetic Xenotime. Essentially all other radioisotope techniques are restricted to igneous rocks.Then there's K-Ar dating, beloved of creationists and almost the only one they ever discuss. K-Ar does require an "assumption" of no radiogenic argon at solidification, but since argon is a gas this is almost always a good "assumption". But some errors have occurred because of "excess argon". However, any sample that can be dated by K-Ar can also be dated by Ar-Ar, an isochron method, and this is often done.K-Ar dating is quite low cost and simple, and is still done, but is essentially never published today without the cross-check of another dating method. For some examples of rocks dated by multiple methods, see Consistent Radiometric dates and Radiometric Dating.For a fascinating confirmation of the accuracy of Ar-Ar dating, see Precise dating of the destruction of Pompeii proves argon-argon method can reliably date rocks as young as 2,000 years and 40Ar/39Ar Dating into the Historical Realm: Calibration Against Pliny the Younger (free registration required for full text).

FWIW, here's some real isochron diagrams: Some Real Isochron Graphs. Comments:Each data point is a sample, and all samples on a graph were analyzed by the same technique.Some of these are a little old, and the straight-line fit to the data might not be good enough to pass muster today.Note that the Y-intercepts of the graphs for each parent-daughter pair are approximately the same.

David Ewan Kanaha, in the first link below, says 10⁹ degrees K.Some links that are relevant to your post: Modifications of Nuclear Beta Decay RatesRe: Some more on radioactive decay, and my references Changing Decay Rates?[This message has been edited by JonF, 11-17-2003]

Woodmorappe/Peczkis has written a large-format book of about 90 pages, "The Mythology of Modern Dating Methods", in which he gives some fairly detailed criticisms and a lot of quote-mining and misrepresentation, as is his wont. Kevin Henke has posted several rebuttals to parts of this book, many at No Answers in Genesis (there's a search box near the bottom of the page). The most common cause of a false isochron is a mixing isochron, where two sources with different isotopic makeup mix. There's a good discussion and simple example at Isochron Dating: Mixing of Two Sources. You might have to read the beginning part to understand the notation.Some creationist once published a scenario in which he demonstrated that mixing of three sources of peculiar composition (IIRC, one source had to contain only radiogenic daughter and no other isotopes of the daughter, which never happens) could form an isochron and the mixing plot described in the reference above wouldn't detect it. I can't find a reference now. But the idea that such things happen regularly is pretty ludicrous.IMHO, the major indicator of the reliability of radioisotope dating is the excellent correlations between different radioisotope methods and the excellent correlations between radioisotope methods and non-radioisotiope methods.

Not 100% true, but close. I and others had a discussion (on talk.origins) of isochron dating with an old-Earth young-life creationist that lasted from around January 2002 well into 2003 (and left her still convinced that the ages we get are not solidification/closure ages, but are rather some echo of the early Earth that survives through melting and mixing). (The long duration is misleading, since it took incredibly long to get most ideas across to her ... IIRC it took over a month to convince her that division by zero is undefined in the kind of math we use in dating).And, of course, the Woodmorappe book I mentioned "addresses" pretty much the gamut of dating methods.

Gobbledygook.We don't date porous rocks, except for a very special few cases (such as diagenic xenotime dating of sedimentary rocks), in which the xenotime that is dated is a very small portion of the rock and is not itself porous.Isochron methods and concordia-discordia methods, by far the vast majority of methods used today, essentially always detect when samples have been affected by leaching or other changes since solidification (more technically, closure). Discordia dating can often supply a valid age even when the samples have been affected by such changes. These are age-diagnostic methods which almost always detect when the samples are invalid. This has been pointed out several times, and you have ignored it.In other words, your criticism is a pipe dream. It has no validity or grounding in the real world. Please do not offer criticisms until you have learned something about that which you are criticising. If you have questions we'll be glad to answer them, but your pronouncements are so far completely content-free.[This message has been edited by JonF, 01-13-2004]

Yes, basalt is one kind of rock that is dated; but no, it's not particularly porous, and water does not flow through it to any great extent. It can act as if it were porous due to fracturing, but it's pretty easy for a geologist to collect unfractured samples. The same for the many other rocks/minerals used in radioisotope dating.At Rock properties I find a table that shows basalt as 0.1% to 1.0% porosity, and granite as 0.5% to 1.5% porosity; that's not very porous for either type, and the granite is more porous than the basalt. I do not know how acurate this reference is, and I do not have other references to hand.I don't know why you are referencing advertising copy on a dietary supplement page, or why you are bringing up tritium. Tritium has a half-life of about twelve years and has no relevance to radioisotope dating. MTBE also has no relevance to radioisotope dating.If you want to demonstrate a problem for radioisotope dating, you need to demonstrate that the 20 or so isotopes are added to or removed from solid un-fractured un-weathered rock in exactly the correct amounts to make multiple radioisotope methods agree and fit the "deeper is older" obervation and make the age agree with non-radiometric methods. Argon, potassium, samarium, neodynium, uranium, lead, thorium, strontium, rubidium, all in multiple isotopes, and a few more I can't think of right now ... and you've got to show that this happens to every rock, not just some rocks. That's a tall order. Vague claims about flow and porosity and diffusion won't cut it. Relevant EVIDENCE is what's required. Most of what you've posted is irrelevant, and the rest is merely wrong.Learn something about radioisotope dating before you criticise it.[This message has been edited by JonF, 01-13-2004][This message has been edited by JonF, 01-13-2004]

There is tritium in lots of groundwater and in other places, generated relatively recently by cosmic rays and various human activities. Tritium Information Section, Fact Sheet on Tritium.I have my doubts that the claimed carbon-dating is valid or meaningful, but the page is just an advertisement, and isn't much use as a source of information.

Nitpicking: you are correct for so-called "mineral" analysis, and all concordia-discordia dating is mineral analysis because it only works on particular minerals. Some kinds of isochron analysis may be "whole-rock" in which each sample is composed of several minerals; generally an entire rock minus its weathered outer portion. In whole-rock analysis the bulk porosity could be important, but is not because the bulk porosity is so low.

In re basalt, nice hand-waving. Now all you have to do is present some EVIDENCE that this actually occurs in basalt and affects the results of radioisotope dating. Note that you need address the question why would so many different elements and isotopes be added or removed in exactly the correct proportions to make so many different methods agree, and follow the "deeper is older" rule?As for the zircons, the votes aren't quite all in on that yet, but it is virtually certain to be another creationist deception. What about Humphreys excess helium arguments, Re: helium in zircons means young earth?.[This message has been edited by JonF, 01-14-2004][This message has been edited by JonF, 01-14-2004]

Not at all. In order to support your thesis, that all the dates are wrong, you need to answer at least the following questions.Are there such pores in all the rocks that we measure? (hint: the answer in "no").Since not all rocks have such pores, what other effect is acting?Exactly what effect does water in the pores have?How does this effect change the interior of the rock away from the pores? Diffusion is too slow. Micropores or not, the interior of the rock is relatively far away from any pore in non-porous rocks,Why does this effect happen to all rocks?How does this effect act in such a way so as to fool so many different dating methods? Note that this effect must differentiate between isotopes of the same element, and diffusion/leaching does not do that. No known chemical process does that to the extent required. Gibberish about tidal forces and solute concentrations is meaningless. Why does this effect always change the concentration of different isotopes of the same element in exactly the way required to fool the age-diagnostic dating methods?How does this effect act so as deeper rocks measure as being older?

Yes, it is in some rocks. There are lots of scientific facts in this world, and almost all of them are not relevant to radioisotope dating. You need to establish relevancy. And vague pronouncements about capillaries and roots and water are not relevant. Explaining observed facts is relevant, and you haven't tried to do that yet. Yes. So what? Why do you think this is relevant?First, inside solidified rocks (which is where we look when we do dating, micro-pores notwithstanding) the process is so slow that it takes longer than the 4.5 billion year age of the Earth to finish or even have a significant effect.Second, equalizing solute concentrations will not fool modern radioisotope methods.Let's start with an example: rubidium-strontium isochron dating. We take several (often 6 or 7) samples of rocks and/or minerals, sometimes from one rock the size of a baseball and sometimes from several rocks from an area several miles across (but obviously part of the same lava flow). We measure the amounts of Rubidium-87 (or 87Rb), Strontium-87 (or 87Sr) and Strontium-86 (or 86Sr) in each sample. For each sample, we plot a point on a graph where the ratio of 87Rb to 86Sr is the X-axis and the ratio of 87Sr to 86Sr is the Y-axis. The points lie on a straight line, the "isochron line". The slope of the line indicates the age of the rock.In order to fool this system , you need to show us a process that "knows" how much 87Rb, 87Sr, and 86Sr is in every bit of rock for several miles around and adjusts the amount of those species throughout the area so the straight line relationship is maintained but the slope is less. As if that's not enough, this process must "know" to adjust the ratios differntly in adjacent but different lava flows and operate on every lava flow in the world, exposed and buried.But wait, there's more, This process must operate in the same manner on four or five other triplets of elements and isotopes, because we do isochrons on them too.But it gets tougher! Different methods agree on the age of the same rock, so this process must reduce the slope of each of five or six different isochron lines to exactly the same amount.Now the next hurdle ... concordia-discordia. I'm not even going to try to describe that in this medium, but it requires a process that maintains more complex relationships among the quantities of two isotopes of uranium, one isotope of thorium, four isotopes of lead, and several intermediate decay products ... and maintains the consistency with all the isochron methods.Finally we need a process that maintains the consistency between radiometric methods and non-radiometric methods ...And this process has to operate on every igneous rock on Earth!Needless to say, diffusion and/or equalization of solute concentration and/or leaching cannot do this. There is no known process or combination of processes that can do this consistently enough to fool us. You are looking for a process or processes that have never been observed or conceived of by thousands of honest, intelligent, and educated people looking for just such a process over the last hundred years or so.Your babbling about capillaries and water and roots is like a two-year-old trying to tell Einstein that he was all wrong about relativity. You don't know enough about the subject to even start the conversation. Stop talking about sediments. As far as we are concerned in this discussion, we never date sedimentary rock by radioisotope methods. We date igneous rocks above, below, and intruding into sedimentnary rock. We are talking about igneous rocks above, below, and intruding into sedimentary rock. Not sediments We've demonstrated their lies, and pointed you to where more are demonstrated. We've give brief descriptions of the truth, and pointed you to where you can learn more and investigate for yourself. What you really mean is "it appears to me that the creationists make me feel warm and fuzzy by agreeing with my preconceptions".[This message has been edited by JonF, 01-14-2004]

As I pointed out already, your scenario does not explain the what we see. In fact, it is contradicted by our observations. Therefore, it is not a meaningful scientific hypothesis.The mainstream scientific theories explain the evidence very well ... and there's a lot of evidence that they explain well.Please address the observations and evidence or don't bother posting. We've heard plenty of unrealistic fairy tales made up without reference to the real world, we don't need any more.

It's also pretty likely that any "explanation" they could produce would be superficially more convincing but no more valid at its core than Mr. whatever's.

All of which, of course, is irrelevant to the subject under discussion.The subject under discussion is radioisotope dating and its accuracy, which you have totally failed to even discuss, much less criticize. Your irrelevant and meaningless pronouncements are extremely tiresome. Might be ... but is not.