OneLastBreath said:
Chi_Cygi, correct me if I'm wrong here (and I very well could be), but I was under impression that the only useful form of radioactive dating is carbon-14 dating, since measuring the number of half-lives that have passed requires comparing it to another element/isotope that was found in equal amounts as the radioactive element/isotope in the thing being studied. Carbon-14 dating is can only be used to date the age of carbon-based lifeforms that obviously had to be living at some point, not meteors. And also, any form of radioactive dating, if there are others, tends to lose its accuracy as you start measuring things older than around 50 000 years, as measuring 0.00002% compared to the non-radioactive element is extremely difficult. Though by the way, I do agree with the idea of Old Earth Creationism, so I'm not being ambivalent in this issue.
edited to add context
Chi_Cygni mentioned several forms of radioactive dating. Here are a few details that may help.
Each radioactive element has what is called a "half-life". this is the amount of time that it takes for half the original sample to decay. For example, if I have a 10 pound sample of uranium, and so do you, but yours is divided into 10 1 pound samples. Then after 1 half life has occurred, my 10 pound sample will have decayed to only 5 pounds (the other 5 pounds has changed into something else), and your 10 1 pound samples have decayed to half a pound each, for a total of 5 pounds.
There is a fairly simple mathematical formula for all this, which can be solved on a scientific calculator. By using the formula, you can work problems where the time is not one half life, and the amount is a fraction other than one half.
In the case of Carbon-14, because we are working with small samples to begin with, it is generally used to go out to 10 half lives. By taking a sample, and dividing it in half 10 times, we have a fraction of 1/1024. Of course, the percent error that any measurement of the mass of Carbon present, and what percentage of that is C-14, have to be taken into account in order to come up with the margin of error in the date.
C-14 has a half-life of about 5730 years, so 10 half lives would be 57,300 years. C-14 is normally not used to attempt to date things which are older than this.
Uranium-238 has a half life of about 4.5 billion years, eventually decaying through 14 intermediate steps until it is lead. Potassium - Argon has a half life of 1.27 billion years. So these two methods would be used to date fossils that were possibly hundreds of millions of years old. Actually, the fossils are not usually dated, lava above and below the fossil would be dated, and the age of the fossil would then be between those two dates.
C-14 is useful for dating archeological items, because its date range covers prehistoric and historic human activity.
I, and probably a lot of the others reading this, could write a lot more on the subject, but I may have gone too deeply into it already. There are also a lot of good web sites explaining this.
If you want more info, please ask.
Ron