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Radiometric Dating or How Old is that Rock?
Radiometric dating gives the Earth an age of about 4.5 billion years and the Universe an age of about 17 billion years. The accuracy of radiometric dating is often checked by comparing the radiometric date with non-radiometric dates of objects, such as historical accounts, tree rings, ice cores, etc. These results repeatedly demonstrate the validity of radiometric dating.
There are over 40 different radiometric dating methods. Each has it own application, limitations, and dating range.
See also How Old is the Earth? for a more detailed discussion
See also Young Earth Evidence
General history of radiometric and Carbon-14 dating
In depth description of dating written for Christians
An Essay on Radiometric Dating By Jonathan Woolf
Other radiometric dating sites
How do we know that radiometric dating methods are accurate?
The accuracy of radiometric dating is often checked by comparing the radiometric date with non-radiometric dates of objects, such as historical accounts, tree rings, ice cores, etc. These results repeatedly demonstrate the validity of radiometric dating. Carbon-14 dating has been extensively tested against known historical items, such as King Tut's wooden coffin, with excellent results. See Lake Suigetsu Algae for another such example. While there are occasional false dates caused by contamination and leaching, overall, radiometric dating has been demonstrated to be very accurate. Critics make much use of these false dates. But just because radiometric dating doesn't work every time, this doesn't mean that it doesn't work. After all, just because Detroit produces a lemon once in awhile, that doesn't mean they can't make cars.
The accuracy of argon radioisotope dating has been verified by testing it against known volcanic eruptions showing that it is accurate.
Event Biblical events have been accurately dated using Carbon-14. A tunnel believed to be built by King Hezekiah and described in the Bible (Kings II 20:20; Chronicles II 32:3, 4), was dated using carbon-14 and uranium-thorium dating to show that it was built near the time of the Judean king (700 B.C.).
The Dead Sea Scrolls: Some papyrus manuscripts contain exact dates when they were written and others have been dated using paleography, a method of determining a date from the style of characters. Carbon-14 dating gives the same dates.
Also the samples are dated using various isotopes giving matching results. If radiometric dating wasn't accurate, then for this to happen, the decay rate for each different isotope would have to have changed by the same amount and contamination and leakage of many different elements in the sample would have to be equivalent.
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Criticisms of Radiometric Dating
The rate of radioactive decay is not constant and was faster when the Earth was young, therefore giving a false indication of old age.
For radiometric dating to be accurate, one has to know how much of the parent and daughter elements were present when the decaying started.
For radiometric dating to be accurate, one has to know how much of the parent and daughter elements either escaped or were added since the decaying started.
Since all matter was created at once, shouldn't everything have the same date?
Why are some radiometric dates so far off of what we know they should be, such as recent lava flows that give incredibly old dates.
The RATE project has assembled a group of scientists to investigate the accuracy of radioisotope dating. They claim to have found evidence to disproving its accuracy and have produced the video Radioisotopes and the Age of the Earth based on these results.
Fossil wood found in ancient limestone (Hawkesbury Sandstone)
Answers to the criticisms
What is the evidence that decay rates have remained constant?
The stars provide an observable record of radioactive decay.
It has been shown that slight changes in decay rate are possible. And it may even be be possible that yet unknown mechanisms have changed the decay rates. However, this would have severe consequences. Every time an isotope decays into its daughter element a certain amount of heat is released. If the decay rate increases, the same total heat is released, just over a shorter period of time. Right now, this heat keeps the Earth's core molten. Otherwise the Earth would have cooled billions of years ago. In fact, before nuclear energy was understood, Lord Kelvin calculated that the Earth would have cooled in a only few hundred million years (he, of course, didn't know about nuclear heating in the core). If the decay rate had increased by the amount suggested by the Young Earth Creationists, then the heat released would almost certainly have evaporated the Earth. While it is possible that the decay rates have not been perfectly constant, even changes of a few percent would have dire consequences for the Earth. To imagine that it is off by a factor of 450,000 as required by the claims of the Young Earth Creationists is about as improbable as something can get.
How can we know how much of the parent and daughter elements were present when the decaying started?
U-235 and U-238 provide a means to verify the assumption of how much of the parent and daughter elements the sample started with.
Potassium-Argon dating - Argon does not react chemically, so any found inside a rock is very likely the result of radioactive decay of potassium.
The most accurate test of the assumptions about the starting parent and daughter elements is to date the sample using multiple methods. Since the dating methods use different parent and daughter elements, it is highly unlikely that the sample could be contaminated in a way that would affect the different methods in such a way as to all give the same wrong date. Matching dates provide strong evidence that the initial assumptions were correct.
The following applies to minerals. It does not apply to some of the other techniques, such as Carbon-14 dating.
Isochron dating does not even require knowing the starting amounts, thus eliminating this criticism altogether.
Why are some radiometric dates different from what they should be, such as recent lava flows that give incredibly old dates.
I dropped my watch in water and it stopped, so I went to store to purchase another. As I looked at the watches on display, I noticed that while most kept good time, some were many hours off. Behind the counter was a man repairing watches. Apparently some watches consistently give the wrong time. Water immersion had caused my watch to not work at all. I realized I had no choice - I immediately left the store without a new watch. After all, I had just proved that watches can't keep time!
I've got 100 watches. Ninety-nine give the same time, one is wrong. Does that prove that watches can't keep time?
That's the criticism in a nutshell. Radiometric dating occasionally doesn't work, therefore it must not work at all. This is clearly absurd.
Certainly radiometric dating has its limitations. There are known conditions that will induce error in the dating, such as contamination and leaching. Sometimes it's possible to tell in advance when a specimen can't be dated properly, other times it's not. Consequently, some samples are going to give false dates. It's just a fact of life. Just like medical tests that sometimes give false positives. Does this mean the test is worthless, or does it simply mean it has limitations and should be used with caution? Detroit makes millions of cars each year. Some of those cars are lemons. Do a few lemons prove that Detroit can't make cars? Geologist will tell you to cross check dates with other dating methods to verify that it's not a lemon. But the vast majority of radiometrically dated samples give accurate and consistent dates. The exceptions don't mean that the method is invalid, just that it's not perfect and a little common sense should be used.
See a detailed example of some failed Mt. St Helens lava datings and an explanation of why they failed (with diagrams)
Creationists sometimes take advantage of the known conditions that will produce false dates. They will gather samples that meet the conditions known to produce false dates and then hold it up as "proof" that radiometric dating doesn't work. See Radioisotopes and the Age of The Earth for examples of this.
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Since it has a relatively short half life of 5,730 years, it is used to date relatively recent items, usually less than 40,000 years.
Carbon-14 (C-14) is a radioactive isotope of carbon-12. Carbon-14 is continuously created by cosmic rays bombarding nitrogen in the upper atmosphere. The atmospheric carbon dioxide (CO2) contains this C-14. Living organisms then acquire carbon from carbon dioxide while they are living. When the organism dies, the C-14 begins to decay into nitrogen-14. The proportion of carbon-14 remaining give an indication of how long ago it died.
While the rate of creation of C-14 appears to be roughly constant, there are factors that affect it.. Volcanic eruption, or other events that give off large amounts of carbon dioxide, can reduce local concentrations of C-14. The ratio of C14 has also been reduced by a few percent due to the release carbon dioxide by industry. It is also affected by solar wind and the earth's magnetic field. These factors are known to affect the accuracy by as much as 5%.
Critics of C-14 dating make much of the difference in C-14/C-12 ratios across time. However, they usually conveniently fail to mention that these factors only affect the date by a few percent. An item dated as 30,000 years old would be off by only 1 - 2,000 years due to changes in C-14 ratios. Also, much research has been done to determine the past values for this ratio. Numerous items whose dates are historically know have been C-14 dated with excellent results. See Accuracy for examples of these.
2006-01-15 Anonymous (Atheistic Evolutionist) wrote
2006-01-31 Anonymous (Young Earth Creationist) wrote