Assumptions of Radioactive Dating • Smilodon's Retreat
I would think that the older the sample, the larger the overestimate. .. Other than radiometric dating, I didn't see any significant geologic datasets that pointed Many radioactive dating systems start with an assumption about what . A Perfect Example of Critical Thinking · Homeschooling and Socialization. Uranium-lead dating method at the Pará-Iso isotope geology laboratory, .. The Th/ Th ages are found to be critically dependent on corrections for . its associated error in thermoluminescence (TL) dating requires assumptions to be sexual feelings Dating and sexual feelings Thinking about romance, starting to. Some people think that the various dating methods (uranium, carbon 14, etc.) .. It is only an assumption that integral or adjacent lead could only be an end- product. . (See "Critical Examination of Radioactive Dating of Rocks," in Creation.
The rock being dated must remain a closed system with respect to uranium, thorium, and their daughter nuclides for the method to work properly. Both the uranium and thorium series include nuclides of radon, an inert gas that can migrate through rock fairly easily even in the few days it lasts. To have a radiometric dating method that is unquestionably accurate, we need a radioactive nuclide for which we can get absolutely reliable measurements of the original quantity and the current quantity.
Is there any such nuclide to be found in nature? The answer is yes. Which brings us to the third method of radiometric dating. Only K40 is radioactive; the other two are stable. K40 is unusual among radioactive nuclides in that it can break down two different ways. It can emit a beta particle to become Ca40 calciumor it can absorb an electron to become Ar40 argon Argon is a very special element.
Argon is a gas at Earth-normal temperatures, and in any state it exists only as single atoms. By contrast, potassium and calcium are two of the most active elements in nature. They both form compounds readily and hold onto other atoms tenaciously. What does this mean? It means that before a mineral crystallizes, argon can escape from it easily.
It also means that when an atom of argon forms from an atom of potassium inside the mineral, the argon is trapped in the mineral. So any Ar40 we find deep inside a rock sample must be there as a result of K40 decay. That and some simple calculations produce a figure for how long the K40 has been decaying in our rock sample.
What happens if our mineral sample has not remained a closed system? What if argon has escaped from the mineral? What if argon has found its way into the mineral from some other source? If some of the radiogenic argon has escaped, then more K40 must have decayed than we think -- enough to produce what we did find plus what escaped.
In other words, a mineral that has lost argon will be older than the result we get says it is. In the other direction, if excess argon has gotten into the mineral, it will be younger than the result we get says it is. An isochron dating method isochron dating is described in the next section can also be applied to potassium-argon dating under certain very specific circumstances.
When isochron dating can be used, the result is a much more accurate date. Yet a fourth method, rubidium-strontium dating, is even better than potassium-argon dating for old rocks. The nuclide rubidium Rb87 decays to strontium Sr87 with a half-life of 47 billion years. Strontium occurs naturally as a mixture of several nuclides.
If three minerals form at the same time in different regions of a magma chamber, they will have identical ratios of the different strontium nuclides. The total amount of strontium might be different in the different minerals, but the ratios will be the same. Now, suppose that one mineral has a lot of Rb87, another has very little, and the third has an in-between amount.
That means that when the minerals crystallize there is a fixed ratio of Rb This changes the chemical identity of the atom. It is no longer Rb; it is strontium Sr Sr is not radioactive, so the change is permanent. We know how long it takes Rb to turn into Sr, so in principle, if we analyze the amount of Rb and Sr in a rock, we should be able to tell how long the decay has been occurring.
Of course, there are all sorts of uncertainties involved. How much Sr was in the rock when it first formed? Was Rb or Sr added to the rock by some unknown process? Was one of them removed from the rock by some unknown process?
The isochron is supposed to take care of such issues.
An Essay on Radiometric Dating
Essentially, rather than looking at the amounts of Rb and Sr, we look at their ratios compared to Sr The ratio of Sr to Sr is graphed versus the ratio of Rb to Sr for several different parts of the rock. How does that help? Thus, it provides an independent analysis of the rock that does not depend on the radioactive decay that is being studied.
The amount of Sr that was already in the rock when it formed, for example, should be proportional to the amount of Sr that is currently there. Since the data are divided by the amount of Sr, the initial amount of Sr is cancelled out in the analysis. He says that there is one process that has been overlooked in all these isochron analyses: Atoms and molecules naturally move around, and they do so in such as way as to even out their concentrations.
A helium balloon, for example, will deflate over time, because the helium atoms diffuse through the balloon and into the surrounding air. These conditions are most often met in small, relatively deep lakes at mid to high latitudes.
Shallower lakes typically experience an overturn in which the warmer water sinks to the bottom as winter approaches, but deeper lakes can have persistently thermally stratified temperature-layered water masses, leading to less turbulence, and better conditions for varve layers.
Varves can be harvested by coring drills, somewhat similar to the harvesting of ice cores discussed above. Overall, many hundreds of lakes have been studied for their varve patterns.
Each yearly varve layer consists of a mineral matter brought in by swollen streams in the spring. Regular sequences of varves have been measured going back to about 35, years.
The thicknesses of the layers and the types of material in them tells a lot about the climate of the time when the layers were deposited. For example, pollens entrained in the layers can tell what types of plants were growing nearby at a particular time. Other annual layering methods. Besides tree rings, ice cores, and sediment varves, there are other processes that result in yearly layers that can be counted to determine an age. Annual layering in coral reefs can be used to date sections of coral.
Coral generally grows at rates of around 1 cm per year, and these layers are easily visible. As was mentioned in the uranium-series section, the counting of annual coral layers was used to verify the accuracy of the thorium method. There is a way of dating minerals and pottery that does not rely directly on half-lives. Thermoluminescence dating, or TL dating, uses the fact that radioactive decays cause some electrons in a material to end up stuck in higher-energy orbits.
The number of electrons in higher-energy orbits accumulates as a material experiences more natural radioactivity over time. If the material is heated, these electrons can fall back to their original orbits, emitting a very tiny amount of light. If the heating occurs in a laboratory furnace equipped with a very sensitive light detector, this light can be recorded.
The term comes from putting together thermo, meaning heat, and luminescence, meaning to emit light. By comparison of the amount of light emitted with the natural radioactivity rate the sample experienced, the age of the sample can be determined. TL dating can generally be used on samples less than half a million years old.
TL dating and its related techniques have been cross calibrated with samples of known historical age and with radiocarbon and thorium dating. While TL dating does not usually pinpoint the age with as great an accuracy as these other conventional radiometric dating, it is most useful for applications such as pottery or fine-grained volcanic dust, where other dating methods do not work as well. Electron spin resonance ESR.
Also called electron paramagnetic resonance, ESR dating also relies on the changes in electron orbits and spins caused by radioactivity over time. However, ESR dating can be used over longer time periods, up to two million years, and works best on carbonates, such as in coral reefs and cave deposits.
It has also seen extensive use in dating tooth enamel. This dating method relies on measuring certain isotopes produced by cosmic ray impacts on exposed rock surfaces. Because cosmic rays constantly bombard meteorites flying through space, this method has long been used to date the ' flight time' of meteorites--that is the time from when they were chipped off a larger body like an asteroid to the time they land on Earth.
The cosmic rays produce small amounts of naturally-rare isotopes such as neon and helium-3, which can be measured in the laboratory. The cosmic-ray exposure ages of meteorites are usually around 10 million years, but can be up to a billion years for some iron meteorites. In the last fifteen years, people have also used cosmic ray exposure ages to date rock surfaces on the Earth. This is much more complicated because the Earth's magnetic field and atmosphere shield us from most of the cosmic rays.
Cosmic ray exposure calibrations must take into page 19 account the elevation above sea level because the atmospheric shielding varies with elevation, and must also take into account latitude, as the magnetic shielding varies from the equator to the poles. Nevertheless, terrestrial cosmic-ray exposure dating has been shown to be useful in many cases. We have covered a lot of convincing evidence that the Earth was created a very long time ago.
The agreement of many different dating methods, both radiometric and non-radiometric, over hundreds of thousands of samples, is very convincing. Yet, some Christians question whether we can believe something so far back in the past. My answer is that it is similar to believing in other things of the past. It only differs in degree.
Scientist Realizes Important Flaw in Radioactive Dating
Why do you believe Abraham Lincoln ever lived? Because it would take an extremely elaborate scheme to make up his existence, including forgeries, fake photos, and many other things, and besides, there is no good reason to simply have made him up. Well, the situation is very similar for the dating of rocks, only we have rock records rather than historical records. There are well over forty different radiometric dating methods, and scores of other methods such as tree rings and ice cores.
All of the different dating methods agree--they agree a great majority of the time over millions of years of time. Some Christians make it sound like there is a lot of disagreement, but this is not the case. The disagreement in values needed to support the position of young-Earth proponents would require differences in age measured by orders of magnitude e.
The differences actually found in the scientific literature are usually close to the margin of error, usually a few percent, not orders of magnitude! Vast amounts of data overwhelmingly favor an old Earth. Several hundred laboratories around the world are active in radiometric dating.
Their results consistently agree with an old Earth. Over a thousand papers on radiometric dating were published in scientifically recognized journals in the last year, and hundreds of thousands of dates have been published in the last 50 years. Essentially all of these strongly favor an old Earth. Radioactive decay rates have been measured for over sixty years now for many of the decay clocks without any observed changes. And it has been close to a hundred years since the uranium decay rate was first determined.
Both long-range and short-range dating methods have been successfully verified by dating lavas of historically known ages over a range of several thousand years. The mathematics for determining the ages from the observations is relatively simple.
The last three points deserve more attention. Some Christians have argued that something may be slowly changing with time so all the ages look older than they really are. The only two quantities in the exponent of a decay rate equation are the half-life and the time. So for ages to appear longer than actual, all the half-lives would have to be changing in sync with each other. One could consider that time itself was changing if that happened remember that our clocks are now standardized to atomic clocks!
Beyond this, scientists have now used a "time machine" to prove that the half-lives of radioactive species were the same millions of years ago. This time machine does not allow people to actually go back in time, but it does allow scientists to observe ancient events from a long way away. The time machine is called the telescope. Because God's universe is so large, images from distant events take a long time to get to us.
Telescopes allow us to see supernovae exploding stars at distances so vast that the pictures take hundreds of thousands to millions of years to arrive at the Earth.
So the events we see today actually occurred hundreds of thousands to millions of years ago.