See also Counterexamples to an Old Earth.
Radiometric dating is a method of determining the approximate age of an artifact by measuring the amount of radioactive decay that has occurred. Radiometric dating requires careful analysis and control over the isotopic mix of atoms in the original sample, as well as careful analysis and control of factors e.
These difficulties are considerable, and "Non radiometric dating accuracy" discussed below. It also requires knowledge of the rates at which various isotopes decay. These rates known to great accuracy.
Because analysis of the various control variables that could affect the chemical composition of the sample during the decay period often depends on shrewd guesswork, radiometric dating as a whole could be said to fail the standards of testability and falsifiabilityand so claims based on radiometric dating may fail to qualify under the Daubert standard for court-admissible scientific evidence.
The underlying decay rates, on the other hand, are completely testable and falsifiable. Radiometric dating is more accurate for shorter time periods e. Due to so many different kinds or radiometric dating in use i. Therefore, support for radiometric dating is virtually universal in the scientific community. There are a number of assumptions involved in radiometric dating with respect to long time periods. One key assumption is that the initial quantity of the parent element can be determined.
With uranium-lead dating, for example, the process assumes the original proportion of uranium in the sample is known with reasonable accuracy. One assumption that can be made is that all the lead in the sample was once uranium, but if there was lead there to start with, this assumption is not valid, and any date based on that assumption will be incorrect too old.
So care is required. In the case of carbon dating, it is not the initial quantity that is important, but the initial ratio of C 14 to C 12but the same principle otherwise applies. Recognizing this problem, scientists try to focus on rocks that do not contain the decay product originally.
For Non radiometric dating accuracy, in uranium-lead dating, they use rocks containing zircon ZrSiO 4though it can be used on other materials, such as baddeleyite. Zircon has a very high closure temperature, is very chemically inert, and is resistant to mechanical weathering. For these reasons, if a rock strata contains zircon, running a uranium-lead test on a zircon "Non radiometric dating accuracy" will produce a radiometric dating result that is less dependent on the initial quantity problem.
Another assumption is that the rate of decay is constant over long periods of time. Radiometric dating requires that the decay rates of the isotopes involved be accurately known, and that there is confidence that these decay rates are constant. Fortunately, this is the case.
The physical constants nucleon masses, fine structure constant involved in radioactive decay are well Non radiometric dating accuracy, and the processes are well understood. Careful astronomical observations show that the constants have not changed
Non radiometric dating accuracy in billions of years—spectral lines from distant galaxies would have shifted perceptibly if these constants had changed.
In some cases radioactive decay itself can be observed and measured in distant galaxies when a supernova explodes and ejects unstable nuclei. Indirect observations can allow us to infer radioactive decay rates over time scales that are quite long.
For example, we can measure gamma radiation rates at specific frequencies from distant supernovae and compare this to the rate expected for the mass of the star. This has given rates for supernovae as distant aslight years which are consistent with those measured today. Thus it would seem decay rates have been the same for at least the pastyears. Some people, perhaps in support of a Creationist viewpoint, have suggested that decay rates have changed significantly because "energy levels" have changed significantly.
Whether electron energy levels or nucleon energy levels are being referred to, this is simply not true. There are a few effects that Non radiometric dating accuracy alter radioactive half-lives, but they are mostly well understood, and in any case would not materially affect the radiometric dating results. That is, the analysis of the isotopic and chemical composition of the sample has far greater uncertainty than any uncertainty in the decay rate itself.
The major reason that decay rates can change is that the electric Non radiometric dating accuracy, from the atom's electron cloud, can change due to chemical changes. That is, electrons can move closer to or farther away from the nucleus depending on the chemical bonds.
This affects the coulomb barrier involved in Alpha decayand therefore changes the height and width of the barrier through which the alpha particle must tunnel. The effect of this on alpha decay, which is the most common decay mode in radiometric dating, is utterly insignificant. There is another effect that takes place in the "electron capture" type of Beta decay.
This is an example of the Weak forceand is fairly rare. Electron capture requires that there be an electron in the vicinity of the nucleus, so its activity depends strongly on the configuration of the electron cloud, which depends on the chemical state. In fact, it is possible to shut down electron capture completely—simply "Non radiometric dating accuracy" the substance so that there are no electrons nearby.
There is a fairly well-known example of chemical state affecting electron capture Non radiometric dating accuracy. The 7 Be nucleus Beryllium-7 is an electron capturer with a half-life of about 53 days, turning into Lithium The variation is about 1. While this half-life is way too short to be useful for radiometric dating, the effect of the chemical state is noticeable.
The reason is that, because the atomic number is only four, the 2s valence electrons are very close to the 1s electrons involved in capture. There is another effect, that is not understood. It appears that some radioactive decays are affected the Sun, and fluctuate over a period of about 33 days as the Sun rotates. The variation is about one tenth of a percent.
It has been observed in silicon and chlorine While it is not understood why this happens, it Non radiometric dating accuracy average out over long time periods and therefore not affect the final result. Creationists cast doubt on this analysis, and some apparently believe that decay rates could be so far off by a factor of millions or more that it could explain observations pointing to an old-Earth time-frame while young-Earth cosmology was actually taking place.
They cite large numbers of articles on Creationist web sites. It uses the phenomenon of ionization, described above, to shut down electron capture decay, which could indeed cause a billion-fold discrepancy. However, this ionization would not have taken Non radiometric dating accuracy under real-world circumstances. The Walker and Knapp articles refer the noticeable discrepancies in Beryllium-7, described above.
Creationists also suggest that decay rates were almost certainly not constant near the creation or beginning of the universe. However, the billions of years of Uranium decay, for example, did not take place near the beginning of the universe.
See Half-life for an explanation of the exponential decay involved in radioactivity, and the meaning of the term "half-life". The exponential decay pattern is the same for all kinds of nuclear radiation— alpha decaybeta decayand gamma decay. This governs what is known as the "decay rate.
This makes different elements useful for different time scales of dating; an element with too short an average lifetime will have too few particles left to reveal much one way or another of potentially longer time scales.
Hence, elements such as potassium, which has an average lifetime of nearly 2 billion years before decaying into argon, are useful for very long time scales, with geological applications such as dating ancient lava flows or rocks.
Carbon, on the other hand, with a shorter mean lifetime of over years, is more useful for dating human artifacts. It is important that the sample not have had any outside influences. One example of this can be found in metamorphic rocks. For example, with Uranium-lead dating with the crystallization of magma, this remains a closed system until the uranium decays.
As it decays, it disrupts the crystal and allows the lead atom to move. Likewise, heating the rock such as granite forms gneiss or basalt forms schist. This can also disrupt the ratios of lead and uranium in the sample. In order to calibrate radiometric dating methods, the methods need to be checked for accuracy against items with independently-known dates.
Carbon dating, with its much lower maximum theoretical range, is often used for dating items only hundreds and thousands of years old, so can be calibrated in its lower ranges by comparing results with artifacts whose ages are known from historical records.
Scientists have also attempted to extend the calibration range by comparing results to timber which has its age calculated by dendrochronologybut this has also been questioned because carbon dating is used to assist with working out dendrochronological ages.
Otherwise, calibration consists of comparing results with ages determined by other radiometric dating methods. However, tests of radiometric dating methods have often shown that they do not agree with known ages of rocks that have been seen to form from volcanic eruptions in recent and historic times, and there are also examples of
Non radiometric dating accuracy dating methods not agreeing with each other.
Young earth creationists therefore claim that radiometric dating methods are not reliable and can therefore not be used to disprove Biblical chronology. Radiometric dating methods are widely quoted by scientists, giving, for example a Creationists suggest an age for the universe and the Earth of about thousand based on the Bible  .
As with all scientific endeavors, one needs to be careful in "Non radiometric dating accuracy" the data. Carbon dating is particularly subject to misinterpretation, because biological processes are involved. A geological guidebook published by the Queensland government acknowledges that the dates are not absolute, but must be interpreted:. One example Non radiometric dating accuracy scientists not accepting radiometric is that of Mungo Mana human fossil from New South Wales.
When originally found, it was dated by radiocarbon dating at around 30, years old. This was later revised to 40, years. Another scientist later used other methods to derive a date of 62, "Non radiometric dating accuracy." The original discoverer, unconvinced by this result, used a different method again, and again came up with a date of 40, years.
So radiocarbon dating is really not very precise. The fallibility of dating methods is also by the fact that dating laboratories are known to improve the likelihood of getting a "correct" date by asking for the expected date of the item. For example, the Sample Record Sheet for the University of Non radiometric dating accuracy Radiocarbon Dating Laboratory asks for the estimated age, the basis for the estimate, and the maximum and minimum acceptable ages.
There are several major types of radiometric dating in use: No method exists for measuring timeexcept by measuring it as it is passing. Therefore, the age of an artifact must be calculated. The basic principle in any dating method is to find a process that is occurring at a Non radiometric dating accuracy rate and which is causing a change, measure the rate of that process, work out what state the artifact was in at the beginning of the process, observe what state it is in now, and to calculate how long the process at the measured rate would need to occur to effect that change.
For example, to work out how long a candle has been burning, the following steps would be needed:. For most radiometric dating methods, one radioactive element changes by a process of nuclear decay into another element often through a number of intermediate steps.
For example, uranium will eventually decay into lead. So to measure how old a specimen containing some uranium and some lead is, the following steps are required:. Radiometric dating or radioactive dating is a technique used to date materials such as rocks or Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geologic time scale.
It is not affected by external factors such as temperature, pressure, chemical environment. Long-age geologists will not accept a radiometric date unless it It relates only to the accuracy of the measuring equipment in the laboratory.
The overall reliability of radiometric dating was addressed in some detail in a recent We scientists who measure isotope ages do not rely entirely on the error .