Radiometric dating as practiced is reliable.
"Radiometric dating (often called radioactive dating) is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates." [1. http://en.wikipedia.org...] It includes carbon dating, uranium/lead dating, potassium/argon dating and more that a dozen other methods using radioisotopes.
The phrase "as practiced" means that the methods are applied according to standard scientific protocols by trained personnel.
"Reliable" means "Consistently good in quality or performance; able to be trusted." "Reliable "does not been invariably perfect. Rulers are a reliable way of measuring objects, but nonetheless erroneous measurements occur and they are not absolutely precise. The claim is that radiometric dating methods are reliable enough for scientific purposes.
Proof of reliability involves comparison to alternative dating methods.
My opponent has agreed not to use Creationist sources in this debate, but to rely upon standard scientific sources.
This opening round is for definitions and acceptance only. I will give the Pro case at the start of the second round.
Standard debate conventions apply. I list them here for the benefit of new debaters and readers. I believe there is nothing tricky or eccentric. Both sides agree to the following rules, and that violating the rules is a conduct violation, with anything contrary to the rules to be ignored by readers judging the debate:
DR 1. All arguments must be made in the debate. Evidence may be cited or linked from the debate, but only in support of arguments made in the debate. Arguments made in Comments are to be ignored.
DR 2. Source links or references must be included within the 8000 characters per round limit of the debate. No links or sources are permitted in comments.
DR 3 Any term not specifically defined before use is to be taken with the ordinary dictionary definition of the term that best fits the context of the debate.
DR 4. No new arguments shall be made in Round 4. Pro may rebut previous arguments using new evidence solely for that purpose, but no new arguments are allowed. Con may not present any new evidence in R4.
DR 5. DDO site rules always apply. Neither side may add or modify rules for the debate once the challenge is accepted.
1. Radiocarbon Dating
Radiocarbon dating was discovered by Willard Libby, a nuclear chemist at the University of Chicago. He announced his discovery of carbon dating in 1949. Scientists immediately wondered if the method was reliable. The tests they applied included many test of ancient artefacts having known dates. The method worked so well and proved so reliable that Libby was awarded the Nobel Prize in Chemistry in 1960. [1. http://en.wikipedia.org...]
Carbon dating only works to date things that were once living. Radioactive carbon 14 is continually generated by cosmic rays in the upper atmosphere. Plants take in the carbon as carbon dioxide, and animals eat the plants. Once carbon 14 is taken out of exchange with the atmosphere, the radioactive carbon starts to decade to stable carbon 12, and the proportion of the radioactive isotope decreases. Measuring the ratio of the isotopes implies the time since the exchange with the atmosphere stopped.
Scientists tested the reliability of the method using blind tests of archaeological artefacts having known dates. The first sample was from Zoser’s tomb at Saqqara, Egypt, dated by archaeologists to be 4,650 years old. The radiocarbon date was within 1%. The second sample, supposedly from the the time of Ptolemy, produced a radiocarbon date of zero. It turned out the ample was from a "reputable dealer" in Cairo, and was a modern fake. In the early 50s hundreds of samples were dated and the reliability of the method established. [2. Macdougall, Doug (2008-05-31). Nature’s Clocks: How Scientists Measure the Age of Almost Everything, University of California Press. Kindle Edition locations 1016-1017].
The many checks of the method showed that the dates being obtained were averaging a few percent too young. Libby did not have the precise half-life of carbon-14. That was corrected., with 5,568 years updated to 5,730 years. At a finer level, dating tree rings showed that the amount of carbon-14 in the atmosphere varied by a few percent due to variation in the level of cosmic radiation. By using overlapping patterns of tree rings, calibration back 11,000 years is achieved. Approximate methods go back to the useful extent of carbon dating, about 40,000 years.
“Carbon-14 dating is now so widespread that there is an entire scientific journal, published three times each year, dedicated exclusively to the results of radiocarbon research. It is called simply Radiocarbon, and a typical issue may contain articles about applications in areas as diverse as archaeology, geology, oceanography, and climate change.” [2. op cit 1207-1209, also http://www.radiocarbon.org...]
2. Uranium-Lead dating
The decay of naturally occurring isotopes is used for dating for dating rocks. “For uranium-lead dating... it is virtually impossible to know the sample’s original content of the radioactive isotope used for dating. So, instead of determining how much of the isotope has decayed away, the important measurement is of the amount of daughter isotope that has accumulated—the product of the radioactive decay. By plugging this value into the radioactive decay equation, together with the present-day content of the radioactive parent (another value that can be measured directly), an age can be calculated.” [2. op cit 1659-1664].
Ultimately it turned out that four quantities should be measured: two isotopes of uranium and their lead decay products. This “provides a kind of built-in cross-check for dating. If ages calculated from each of the two decay paths agree, it is likely that the date is correct. This feature makes uranium-lead dating the most widely used technique for high-precision age measurement.” [2. op cit 2359-2360] The half-life of uranium is 704 million years, so very old rocks can be dated.
One of the practical problems in uranium-lead dating was achieving isolation from environmental lead. By about 1960, the problems had been worked out and reliable dates were obtained. The way that reliability is ensured is by cross-checking among dating methods, and by showing consistent results from different samples.
3. Multiple techniques
“The utility of using multiple techniques was shown dramatically in work by H. Baadsgaard, a professor at the University of Alberta, Canada, and his colleagues in 1993. These researchers used all three methods ... to date samples from a volcanic ash layer in sedimentary rocks from western Canada. By separating different minerals from the ash layer, Baadsgaard was able to find material suitable for each of the dating techniques—zircon crystals for uranium-lead dating, potassium-rich mica for potassium-argon dating, and feldspar crystals for the rubidium-strontium method. When the researchers compared their results, they found no discernible difference among the dates. Three completely independent techniques gave ages of 72.5, 72.5, and 72.4 million years, in each case with a measurement uncertainty of just a few tenths of a million years.” [2. op cit 2369-2372]
As scientists work to get higher precision in the dating they discovered small errors. The zircon crystals used uranium lead dating can “leak” very small amounts of lead near the surface of the crystal. Etching away the surface removes the depleted zircon. Crystals previously dated at 251 million years were re-dated to 252.6 million years. The different minerals were processed at different labs." [3. Mike Walker. Quaternary Dating Methods (p. 5)]
Potassium-Argon and Argon-Argon dating
“When in a molten state, volcanic rocks such as lavas or the crystal components of volcanic ashes will release any 40Ar that is generated by the decay of 40K. Once the rocks or minerals begin to cool, however, argon can no longer escape and is trapped within the mineral crystal lattices where its abundance increases over time. In the laboratory, the 40Ar concentrations in rock samples can be determined by heating them to the melting point in a furnace. ... A second sample is used to determine 40K content using an atomic absorption spectrophotometer or a flame photometer. The ratio between 40K and radiogenic 40Ar then gives an indication of the time that has elapsed since the volcanic event occurred. [3. op cit pp. 58-59]
The Ar/Ar method voids the problem of measuring the amount of potassium in the sample. Ar/Ar dating is a complex process that involves incremental heating and compensation for atmospheric oxygen. When properly performed, the method is reliable. A test was done on sanidine (feldspar) crystals from Pompeii formed during the eruption of Mount Vesuvius:
"... an isochron age of 1925±94 years was obtained. This is in excellent agreement with the Gregorian calendar-based age (1918 cal. years ago) of the eruption. Although excess argon … was present in the sample, this could be detected by careful laboratory analysis of the sanidine and corrected for. This example shows that a sample less than 2000 years old can be dated with better than 5% precision, and validates the 40Ar/39Ar technique as a reliable geochronometer into the Late Holocene." [3. p. 65] The Late Holocene is the last few thousand years.
Checks with non-radiometric methods
We have mentioned tree rings. Ice-cores from Greenland and Antarctica provide dating back over 100,000 years. There are also varves (sediment layers in lakes and estuaries laid down seasonally) and coral growth rings. Recently developed methods include optically stimulated luminescence [4. http://en.wikipedia.org...] that measures the time since a mineral crystal was last exposed to sunlight. Cosmogenic nuclide dating measures how long a surface has been exposed to cosmic rays. [5. http://en.wikipedia.org...]
We know radiometric dating is reliable because it has been checked against dated archaeological objects, bcause different radiometric methods agree, and becaue the radiometric dates agree with independent methods.
The strength of a method lies greatly upon the strength of its assumptions. Therefore, I will challenge the assumptions here first.
This is the equation used in physics when calculating the radioactive age of a material (which I am sure we both have used):
deltaN = -(lambda)(N)delta(t),
where N is the number of radioactive nuclei at time t, lambda is the decay constant and delta is the change in the variable.
The decay constant is related to the half-life by the equation
It is immediately apparent from these equations that there are several assumptions  that are used just for radiometric dating. Cosmic dating is slightly different and I won"t go into that.
Assumption 1: There are no daughter isotopes before formation.
This is clear from the fact that there are no parameters to account for any daughter nuclei. However, is this assumption tenable? This assumption is not the same as that of the assumption that no parent/daughter nuclei has entered/left after formation. However, for all practical purposes, they are indistinguishable. (I will explain why I think it is untenable later, as it is tied with the next)
Assumption 2: If assumption 1 was wrong, we would be able to check out the correct rock age by looking at the other materials.
This assumption, more clearly, states that the rate of decay in different materials is comparable. We are thus able to see if one of the materials have too much or too little of the parent/daughter. Is this assumption tenable?
For assumptions 1-2, Is it tenable? No it is not. Let me give a hypothetical situation to explain myself. Suppose that there were three rocks formed by the same event. One can be dated using Ar-Ar, another, U-Pb, and the third, radiocarbon.
Let us now suppose that all of these contradict assumption 1, in that they all have daughter isotopes/nuclei before formation. Let us also assume that after formation, no contamination occurs. A contamination being the entering/leaving of parent/daughter nuclei.
Let us now suppose that all of these rocks give the same age x. Now we can say clearly that the age of the rock is x, and no one can contradict us, because the rocks check it out. However, in this situation, we know that there has been daughter nuclei at formation. However, let us suppose that those doing the dating had no knowledge of this.
It is clear from this hypothetical thought-experiment that any future scientist dating rocks from this layer would have to calibrate their dates to align with this first experiment.  This is because the first is assumed to be the correct age of the rock, while the others will be assumed to have contamination. This is why all radiometric datings check out with each other. It"s not because they produce the same results, but that they are calibrated  to the same results and anomalies are regarded as contamination. This is true in some cases, but is most certainly wrong in others.
Now I will move on to the third assumption and hopefully that is the last.
Assumption 3: The decay rate is constant
This assumption needs no elaboration. It is pretty straightforward. So now let me use a couple of sources to debunk this. It has been experimentally proven that decay rates are affected by electron density at the nucleus and can vary with the chemical environments of the atom. Measurements of decay rates differ by as much as 1.5%. This clearly shows that decay rates are not constant as assumed . Clearly, it is not as much as the creationists would suggest , but it does make this assumption untenable. There is also other collaborating evidence that the decay rate is not constant .
So why, in the light of all these untenable assumptions, does the dates check out? Does this mean that even if these assumptions were wrong, we would still arrive at the correct dates because they check out? But wait, my thought experiment has already explained this phenomena. It is not a conspiracy, as some would like to believe, it simply is the way science works. Flawed, yes, but we are all human.
However, is it reliable? To understand this, I will use another thought experiment. Suppose a man has three sticks. Each of them corroborate with each other, each calls itself a "meter stick," and each in actuality is a hundred centimeters more than a meter long.
Let us now suppose that this man is on a barren alien world that has mostly nothing other than sand and a few other sticks of varied lengths. (Well, he"d soon die, but that"s not the point) These other sticks calls themselves "meter sticks" as well, but some range from a few centimeters to several meters.
Is this man"s sticks reliable? I mean, he has three sticks which check each other out. Let us now assume that he has this instruction manual that tells him how to build a shelter out of meter long sticks.
Sure, maybe the sticks were a little longer and he"d build a structure a little bigger. But no, this hypothetical shelter can only work if it were made from meter long sticks.
So, would this shelter be reliable? No it wouldn"t. In the same way, radiometric dating is not reliable.
To some readers the phrase "A house of cards" might get the concept through better, but the connotation is totally different.
I do not understand you last paragraph. You state that radiometric dating agree with dated archaeological objects, because as far as I know, radiometric dating is used to date archaeological artifacts, so it cannot corroborate something not independent. As to the other points, I have explained why different radiometric dating methods agree, but not why different independent methods agree. I won"t go into that point now because I don"t have space.
Now back to you.
2. I am personally picking these out by means of logic, prior knowledge, and (what I like to call) reverse reasoning, so no sources needed. I am not using any source for these portions, not creationist, even. When there is a source, then I have not picked it out.
3. For the explanation, I will provide some sources to align as closely as possible this thought experiment with actual data.
4. http://ieeexplore.ieee.org... For something similar, but not entirely the same
5. www.wou.edu/las/physci/taylor/g322/radiometric_dating.pdf (This is rather hard to read due to the format)
Are tape measures viable for measuring length? Tape use assumes the user correctly aligns the end with desired point on the object, the end doesn't slip, the tape doesn't change length, and the person correctly reads the scale. Tape measures can stretch a little and expand and contract with temperature, so the principle of invariant length is clearly false. Separate teams verifying measurements could coordinate. Since these assumptions cannot be guaranteed true at all times, must we denounce the use of tape measures? Obviously not.
The reason that length measurements are valid, and radiometric dating is also valid, is that theoretical objections are overcome in practice with reasonable care. Scientists take more than just ordinary care; they worry about every assumption. To be sure, scientists want to avoid mistakes. But if there is a chronic problem with a method, they want to discover it. The small errors due to the early measurement of the half-life of C-14 were discovered. The small errors in C-14 due to changes in the solar flux were detected and corrected. Every time an error is discovered scientists get to advance science, write a paper, and enhance their reputation. If they publish a false result, then some other scientist will discover the error and publish the discrepancy.
With this understanding, I now consider Con's specific challenges.
How do we know there is no external source of a daughter isotope?
For carbon dating, the assumption is that carbon-14 is only entered into the sample by exchange with the atmosphere. The way Libby checked that assumption was to test the methane in natural gas in comparison to methane from sewage. [2. op cit] Natural gas has been underground for a long time so all the carbon-14 should have decayed. The test showed that it had. The methane in sewer gas is from organic sources that should be in equilibrium with the atmospheric ratio, and tests showed that also was true.
There are a few cases where exchange is known to be a problem, such as certain biological components of soil. Tests of carbon dating versus known dates determines the circumstances when carbon is not completely isolated. The problem circumstances are then avoided.
When the daughter isotope is a gas, as with potassium-argon and argon/argon dating, the gas is purged when the material is molten. The date is then determined from when the material was molten. Scientists use crystals as the sample material to ensure that no gas enters or leaves the sample over time. Intact crystals are selected to ensure there is no intrusion or leakage.
Crystals are also used to ensure the integrity of solid isotopes. Zircon crystals are used for uranium-lead dating because zircons naturally contain a lot of uranium and are extremely resistant to damage. As previously explained, the two uranium isotopes always present provide a cross-check on the dating. The two dates must agree.
How do we know that cross-checking is not forced to agree?
Con implies that scientists systematically throw away data that does not confirm the results they want to get. Scientists are well aware of the potential for that problem, so blind processing [6. http://en.wikipedia.org...] is used systematically. The tests are deliberately made without knowing where the sample came from, so the answer cannot be forced. Libby's original verifications of C-14 dating was done blind, so the carbon dates couldn't be fudged. 
Labs specialize in different methods of radiometry, so the lab won't know what other methods are being used elsewhere with other samples, let alone what dates are being obtained or are expected. 
A good example of cross-checking is the dating of the formation of the Hawaiian Islands based upon radiometric dating of lava flows. [7. http://www.soest.hawaii.edu...] The dates showing a straight line of tectonic drift with time references 22 papers published from 1964 to 1987. Dozens of scientists contributed.
Are radioactive decay rates constant?
Few things in experimental physics have been verified more thoroughly than the invariance of radioactive decay rates. So far, only beryllium, which con correctly cites, has been discovered to have a variation with chemical composition.
Baylor University notes summarize, “The possible effects of changing temperature, pressure, chemical state, and electric or magnetic field strength on the three decay mechanisms relevant to geologic dating have been intensively studied, both theoretically and experimentally. These studies have shown that changing environmental conditions have either no measurable effect or a negligible effect (less than 1%, and that only for 7Be, which decays through electron capture) on the rate at which the decay processes occur [9. p. 86-90]. "There is no evidence that decay constants have changed as a function of time during the history of the solar system" (10. p. 41). “ [8. http://www.baylor.edu...] [9. Dalrymple, G.B., 1991, The age of the Earth: Stanford, California, Stanford University Press, 474 p.] [10. Faure, G., 1986, Principles of isotope geology [2nd edition]: New York, John Wiley & Sons, 589 p.]
As scientists are better able to measure tiny variations in decay rates, it's not too surprising that small variations due to other causes. A periodic variation of 0.3% in decay rates has been reported and is attributed to solar neutrino flux variations.
Con said “the assumption is that the decay rates in different minerals is comparable.” No, the checks, including the ones I cited using different minerals use different elements having different decay rates.
Con says that if three samples are taken from the same place, the second two will be “calibrated” to agree with the first. That is incorrect. The samples are not used in any way to calibrate or adjust the process. The radioactive decay rates are measured independently and published for anyone to use.
Con's reference  has to do with whether the time between particle emissions in radioactive decay are completely random. That has nothing to do with the decay rate. The emissions could be entirely predictable without violating a constant decay rate. It's like counting the number of cars passing a traffic checkpoint each hour. The cars could be equally spaced or randomly spaced without changing the count..
Con's reference  is unrelated to our debate. The word radiometry is used to refer to measuring how much infrared energy from the sun is reflected by the surface of the earth. The article discussed the calibration of satellites that measure the reflected energy.
Can archaeological artefacts be used to check carbon dating?
Con questions if archaeological objects have dates known independently. The ancient Egyptians kept records of the ruling dynasties and the lengths of the periods of the rule of each king, so archaeologists have pieced together a history of ancient Egypt based solely upon the documentary evidence. The earliest dates derived from the records have the greatest uncertainty. The Egyptians typically put wooden boats in the Pharaohs tombs, the wood suitable for carbon dating. When Libby measured the age of the wood, the comparison dates from nearly 5000 years ago were known to within about 200 years, go enough to verify dates within 4%. Since 1950, the Egyptian calendar system has been discovered to rely upon astronomical events that we can determine precisely. This has reduced the uncertainty in the ages as determined independently to about 50 years.
Libby also checked samples from European archeology and redwood trees having known dates. An account of all the samples is given with a graph of the dates with error bounds in given in Libby's Nobel acceptance lecture. [11. http://www.nobelprize.org...]
You bring up the argument about tape measurements. The assumptions that you have brought up have nothing to do with how radiometric dating is performed. Why? This is because there is a known start/end point for the tape. Radiometric dating only has the end point. This is tied to the first assumption I brought up.
I am sure that if errors were discovered, they would be corrected. I"m not suggesting that there is a conspiracy to give false dates in any way. However, the assumptions I have mentioned can never be exposed as giving a "wrong" date simply because it is a basic assumption and .
That being said, I will defend my arguments.
In the first paragraph, you are not talking at all about daughter nuclei/isotopes. Instead, you are talking about something with which I do not dispute. You state that "the gas is purged when the material is molten." However, this is an assumption and has, so far as I could research, never been experimentally proven. (If you do know of a source where this has been proven, please do cite it)
You have cited the example of crystals in relation to the an assumption which I did not make an argument out of. This assumption deals with the entering/leaving of nuclei after formation. My argument was based on the daughter nuclei/isotope argument, which even if you are right in the case of Ar-Ar and K-Ar (which you are not, as far as my research led me), you would still not be right in the case of U-Pb, by any means.
So now (since my argument about daughter isotopes present BEFORE formation has not been addressed) I will discuss the corroboration of dates. However, I will backtrack a little here. I have found, contrary to the assumption that gas is purged, that there are bad dates from K-Ar dating.  From 1, the given dates were discarded because "The age obtained, however, 95 m.y. (Table 1), is geologically unrealistic, for absence of sediment cover, the freshness of the rock and the ages of associated rocks all point to a late Tertiary origin." But why were the dates discarded? Simply because it did not agree with other rock ages. However, since the two dates do not agree, one must be correct. But note that the argument that this particular age is contaminated is an assumption. Furthermore, it is circular reasoning. What is circular reasoning?  It is repeating the premise in a different form as the conclusion. To relate this to the argument at hand, "If a date is wrong, we can test it with associated dates. The date is wrong because we tested it with associated dates." This is the argument in its simplest form. (If you do not agree, please provide a reason)
A question now arises, "Do the dates really agree?" Firstly, I will defend myself. I did not imply anything like "scientists systematically throw away data that does not confirm the results they want to get." Neither do I say that the dates are forced to agree in the sense you make it. Like I said and as  would collaborate, anomalous dates are counted as contamination or false in some way or the other.
I will state here, clearly, that I do not believe dates will always disagree. In most cases they do agree. Thus, I agree mostly with your point that dates are not forced to agree. This however, does not disagree with my statements either.
I will give one example of why I hold to this view. From , we find an example of highly discrepant ages. "[The authors] report Sm"Nd and Rb"Sr mineral isochron ages of amphibolite from the schist belt. The Sm"Nd and Rb"Sr ages are 824 " 43 Ma and 481 " 16 Ma, respectively." How is this data explained? "The Sm"Nd age indicates the timing of peak metamorphism, whereas the Rb"Sr age indicates the Pan-African thermal overprint. The peak metamorphism was related to collision of the Eastern Ghats terrane with the Dharwar-Bastar craton, which occurred during early Neoproterozoic time." But. Is there any evidence for either occurrence? None at all. This is one of the reasons why I hold to the view that dates are "re-calibrated" to fit certain dates. This kind of articles is what I regularly find in journals such as RadioCarbon , which is a very good journal to read, actually.
I will now address the concerns about my sources. My previous round"s  clearly stated that it was something similar, but not the same. Your argument regarding my  still does not address the point that the decay rate is not constant, which argument I will defend following.
However, I will first address the argument relating to my statement "the assumption is that the decay rates in different minerals is comparable." You have brought up some facts which I do not disagree with. This, however, does not in any way negate my statements. Here"s why.
By comparable decay rates, I meant that the decay rates could be checked out against each other and that if one of the dates were wrong, the other ages could be compared with the anomalies. This in itself has to assume that the rate of decay is somehow comparative, not similar, to each other.
Now to the argument regarding variance in decay rates. I do not know the purpose of the phrase "...which con correctly cites..."
Now I will use data from more recently than Baylor, which has a latest reference of 2004. My source will be from 2010.  Quite simply, long-term observation of Si32 and Ra226 show slight fluctuation during different seasons. (This is something you"ve said, but did not cite) Now I have said that these fluctuations are very small, which is something you"ve proceeded to repeat. This, however, does not address my argument that decay rates are not constant. In fact, it is something you agree with. Now I will briefly discuss the implications of a non-constant decay rate.
Current dates must be remeasured to account for this data. It is a known prediction, so widely so that it is held to be fact, that the sun will eventually sputter and die out . By logical syllogism, we can see that the sun was much hotter in the past, and that it logically would have produced much more flares than the present. Sun flares are directly linked to the change in rates.  Since there would have been much more activity in the past, it is logical to conclude that the rates in the past were much different than it is now.
After reading Libby"s lecture, I am still of the same opinion as I was before. This is because it does not address my question. Radiocarbon dating is frequently "archaeologically unacceptable" . This is because the archaeologist does not agree with the radiocarbon dating as compared to his other methods of dating. Radiocarbon dates has to fit into the expected age or be discarded . This is clear proof that radioactive dating is not reliable but do on many occasions fit the correct dates. Such as that found by Libby.
I would like to note a few problems with your sourcing. In the section "How do we know that cross-checking is not forced to agree?" You have a reference 6, then 2, 3, and 7. You provide links for 6 and 7, but not for 2/3. Your 6,7 are quite abrupt in that there is no 5,4, or 1. Thanks.
I"m out of space.
7. Ref. 5
Thanks to my opponent for the opportunity to look into some of the fundamental aspects of radiometric dating. I found it interesting and I hope readers will find the science interesting as well.
I should have explained my reference numbering system. I number references in sequence from the start of the debate, so there is only one ref [n]. So  and  referenced in R3 are the standard texts I cited repeatedly in R2. The numbering continues with  in R3. I'm sorry for the confusion.
What does reliable mean?
The point of my analogy with using a tape measure was to show that a method can be reliable despite there being a number of possibilities for errors. Con's case comprises a list of things that might go wrong with radiometric without evidence that they typically do go wrong or that they are substantial. Failure to properly align the free end of a tape is comparable to failure of assumptions of initial conditions in radiometric dating. Con cited the possibility of tiny variations in radioactive decays rates. The possibilities of a tape measure stretching or expanding and contracting with temperature are comparable to tiny variations in radioactive decay rates. The objections are uncommon insubstantial, respectively, and so do not invalidate the methods.
I think Con is claiming that radiometric dating should judged reliable only if it provides a perfectly accurate measurements every time it is used, no matter the circumstances under which it is used or whether it is used correctly. By that standard, no method of measurement is reliable, We surely could not rely on tape measures, clocks, or thermometers because each has limitations on when and how they are used that require care in their use to get reliable results. We know radiometric dating is reliable because methods using different isotopes cross-check the results, and the results are consistently verified by dozens of non-radiometric methods, ranging from tree rings to optically stimulated electroluminescence.
Scientists document problems
Con's R2 ref. 1 is a paper that discusses an isolated example of a “fine grained” rock that seemed suitable for K-Ar dating, but yielded an incorrect result. The paper dates from 1971, and did not use the now-common practice of sampling a single crystals to minimize errors. Nonetheless, obtaining an erroneous result merited a publication to report the event. All radiometric dating methods require careful use. Publications reveal the circumstances when there are likely to be problems. The publication of an unusual exception shows that the method is reliable overall.
Decay rate variations are insignificant
Con cites publications that show a periodic variation in decay rates with solar activity, probably due to the influence of variable neutrino emissions from the sun. Recall that I cited a large body of scientific literature that verified that radioactive decay rates are constant. [8,9,10] The newly discovered variations produce a peak error of 0.3%, [12. http://www.examiner.com...] and they tend to cancel out over time with the errors varying around an average rate. The accuracy claimed for radiometric dating is rarely greater than 1%, so sources of error much less than 1% do not come into play in any practical way. Con found no evidence disputing the literature that verifies the stability of radioactive decay rates to better than the 1% level required to support the accuracy claimed for radiometric dating.
It often happens that scientific methods have bounds on their accuracy. Einstein proved that Newton's Laws are only approximations. Yet Newton's Laws are still used reliably for delicate computations of things like satellite orbits. the limitations are kept in mind so the results say within the bounds of the methods.
The reason we are debating the reliability of radiometric dating is to potentially provide hope that creationism is correct and that accordingly the earth is really less less than 10,000 years old. Uranium-lead dating shows the earth to be 4.55 billion years old. Potassium-argon dating and many identifies rocks as having last melted hundreds of millions years ago. Other mineral-based methods work to date rocks from tens of millions to a few hundreds of millions of years old. Argon-argon dating and carbon dating are used for objects dating back tens of thousands to a few million years. So if there limitations in the methods that lead to 0.3% errors in the dates of billions of years of years or hundreds of millions of years, or even of objects tens of thousands of years old, is there hope that the earth might really be less than 10,000 years old? No, a 0.3% error in dates of tens or hundreds of millions years doesn't provide a ray of hope for the young earth. Even if the 0.7% variations found only for beryllium isotopes were rampant, it wouldn't come close to doing the job.
Dates are consistent
Con found the abstract of a scientific article that includes a couple of different dates derived from radiometric methods and seems to conclude that they are in conflict. My understanding is that geologists are trying to sort out different geological events occurring from a half billion to a billion years ago. A 1998 article shows multiple dates of the West Falkland granite s to be consistently a little more than 1 billion years old. 13. http://jgs.geoscienceworld.org...] The issue in the paper Con sites is the presence of rocks with different dates, not an inconsistency in the dating methods.
Initial condition assumptions are valid
Con wants to know if the release of gas from molten rock has been experimentally verified, The expansion of gas when pressure is reduced is fundamental physics, and that gas is released in volcanic eruptions is universally observed. It has also been experimentally verified. [14. http://www.psi.ch...]
The ultimate proof of the validity of the assumptions behind radiometric dating is its verification by dozens of other methods of dating. Con doesn't seem to have specific evidence that C14 doesn't decay, that c14 does not achieve equilibrium with the environment, or that C14 can be injected into isolated samples. He doesn't have evidence that any of the assumptions behind other methods are substantially wrong. He seems to only claim that they cannot be proved in every case. that doesn't overcome the bottom line that the methods are found reliable when cross-checked.
Archaeological dating verifies carbon dating
In William Libby's Nobel lecture he presents the results of blind experiments that showed carbon dating to be verified by known archaeological dates and tree rings. Although the Nobel prize committee was convinced, it doesn't measure up to Con's standards. Con cites cautions given by service that performs carbon dating telling archaeologists to collect samples in accord with proper use of the method. It warns that if care is not taken there may be large errors.
The reason that we know when errors occur is that there are valid cross-checks, including known historical dates. For example, Egyptian relics were known to within +/- 200 years. Carbon dating provides an accuracy of +/- 50 years for the objects. The warning is that if the carbon dates a outside of the historical interval, then there is probably a problem with the sample collection procedure. It does not mean that such errors occur very often. They do not. It means the method is made more reliable by continual cross-checking. If one were teaching use of a measuring tape, would be wise to include cautions about crosschecking to improve reliability, per the "measure twice, cut once" adage of carpenters.
My previous objections to Con's references stand. They are unrelated to the debate.
Radiometric dating is not controversial in the scientific community because it is so consistently verified. It is reliable.
I am not claiming "radiometric dating should judged reliable only if it provides a perfectly accurate measurements every time it is used..." I do realize that there will be errors. This is not the point of my argument about its unreliability which I will go into near the end with the Egyptians.
I would just refute one part of the analogy here. The start end of the tape cannot be analogous to the start ratio of radiometric isotopes. This is because time flows in one direction only. We can alway realign the end to fit where we want it to be to get an accurate measurement, within the bounds of uncertainty. Not for radiometric dating. I will discuss this further with the Egyptians.
My R3 ref. 1. still documents anomalous dates, regardless. Now I will proceed to examine the logic behind. You say that erroneous dates merit publication. This does not take into account the frequency with which bad dates are discarded and not reported. I will now let this portion of the matter rest.
Decay rates indeed are small. Furthermore, I have already said that the variations does not permit an earth under 10,000 years (With the assumption of initial conditions). See my R2 Ref. 7. Therefore I agree with your section on decay rates. I will, however, note that the Be variation is not 0.7%, but 1.5%.
Now I will defend my source concerning the consistency of dates. You note an article with discrepant dates. I will note that the dates variations are far less than mine own. My source uses, if I read correctly, a single rock. The dates were obtained from different methods, hence the different explanations. I will now compute the difference in dates in percentages. From my source, (let us take the dates without the uncertainties), we find that ((824-481)/824)*100 =~ 41.6% difference. For your source, ((1135-989)/1135)*100 =~12.86% The difference in percentage points is 28.74. That is a BIG difference. As far as I understand, your source talks about the dates of different rocks in the same location. This is possible. My source is about differing dates within the same rock, which is fascinating and totally different from your source.
I will quote directly from your source 14 to explain what the experiments found.
"As the molten rock ascends from the depths of the Earth, water (and other volatile substances) trapped inside form bubbles in the rock. These bubbles weaken the rock while simultaneously providing a pathway for the gas to escape in a process called "degassing". If the bubbles expand more rapidly than the gas can escape, a volcanic eruption occurs;"
From this it is absolutely clear that degassing does not totally occur if there is an eruption. Thus the assumption is still false.
You state, "Con doesn't seem to have specific evidence that C14 doesn't decay, that c14 does not achieve equilibrium with the environment, or that C14 can be injected into isolated samples. He doesn't have evidence that any of the assumptions behind other methods are substantially wrong." This is simply because I am not disputing most of these points. It is also because I was focusing more on K-Ar and Ar-Ar dating than the others. Now, even if you are right about initial ratios for Ar dating, which you are not, the same assumption still has not been addressed in U-Pb dating. I can hardly say from this that you have provided no evidence that U-Pb initial ratios were the same as Ar ratios. This is simply because you did not focus on that argument.
So now I will focus on the final, most important, claim. Do radiometric dating support archeological dates, or is it a more secondary dating method?
To thoroughly refute this idea, I will be once again using R3 ref. 8. Pro states that the source cautions the use of radiocarbon dating. Which is true. Which also does not explain the last section of the source. After due care is taken, there are times where archeologists will discard the dates. Simply because it does not fit with the chronology of the site. The logic behind this is very simple. If radiocarbon dating does not agree with other methods of dating, radiometric dating is discarded in favor of the other methods.
The implications of this is clear. So clear that I might not need to state it, but I will anyway.
Radiometric dating is secondary to other primary dating methods. This is because it is not as reliable as other dating methods.
Now that I have that cleared, I will discuss the need of an expected sample age and contaminations. In geology, when a sample produces an anomalous date, it is deemed to have contamination. However, due to time, we are unable to prove it. It is therefore an assumption. Furthermore, considering it as contamination is circular reasoning, which I pointed out in the previous round and will repeat here.
"If a sample has an anomalous age, it must have contamination. This sample has anomalous dates. It has contamination."
Thank you for reading to the end.
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