Radioactive dating

[dad1]

The basis for dating using ratios of isotopes is faith based. One example is that if we see an existing amount of parent and daughter material together, it is assumed that the present processes at work today are wholly responsible for all the material.

[Jose Fly]

[Replying to Sherlock Holmes in post #34]
Because I'm interested in your answer. So again....Name one thing, besides your own existence, that you know to be true.

No, I suggest you start a topic in the Philosophy area and clearly state your thesis and question there.

This thread was created to discuss the role played by assumption in radioactive dating techniques.

LOL....figured. You know what the point is and where I was going, but rather than go down that road you opt to deflect and hope it goes away.

Avoiding uncomfortable reality is the creationists' superpower.

I respectfully suggest you start a topic in the Philosophy area and clearly state your thesis and question there, see if it attracts any interest from people.

I suggest you actually answer the question, since you're the one who has been going on and on about "assumptions" and the like.

Let me remind you what the rest of us have been discussing Jose:

The basis for dating using ratios of isotopes is faith based. One example is that if we see an existing amount of parent and daughter material together, it is assumed that the present processes at work today are wholly responsible for all the material.

If you want to discuss something else then go ahead, start a thread and clearly state your thesis and questions.

This is entirely on topic, and I think you realize it but are too afraid to pursue it so you're trying to put a stop to it with the "start another thread" ploy.

I guess I could be wrong and perhaps you really don't see any connection to my question, the topic of this thread, and the creationists' responses to it. If that's the case, then....well....I'll let that speak for itself.

Should I assume the latter?

[otseng]

but are too afraid to pursue it so you're trying to put a stop to it with the "start another thread" ploy.

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[Sherlock Holmes]

Here's a thought provoking article on things that do influence half-life.

Note how gravitational time dilation is included, the same effect that must be compensated for in the atomic clocks used by the GPS system for example.

Any claims of constancy over long time periods must therefore be carefully scrutinized.

[Jose Fly]

Any claims of constancy over long time periods must therefore be carefully scrutinized.

And you don't think the scientists who work in these fields have done, and do that already? Otherwise, why do you feel the need to say that?

I keep getting the impression that you think scientists do little more than sit around tables making things up, and then go home.

Also, I take it that you really don't want to reply to my request for you to name one thing that you feel you actually know to be true. As the lawyer saying goes, the questions you avoid reveal more than the ones you answer.

[DrNoGods]

[Replying to Sherlock Holmes in post #43]

Note how gravitational time dilation is included, the same effect that must be compensated for in the atomic clocks used by the GPS system for example.

This is not a change in the actual radioactive decay rate, but in the measurement of it by an observer that is not traveling at the same high rate of speed as the decaying atoms. If you were traveling with the decaying atoms at their speed you would not measure a different decay rate. Since most radiometric dating is done using alpha or beta decay, and not electron capture, those small changes are not relevant. And no dating is done while travelling anywhere near speeds where time dilation would need to be considered. Also note the last paragraph of the article (underline mine):

"When reference books list values for the half-life of various materials, they are really listing the half-life for the material when its atoms are at rest, in the ground state, and in a particular chemical bonding configuration. Note that most changes to the half-life of radioactive materials are very small. Furthermore, large changes to a half-life require elaborate, expensive, high-energy equipment (e.g. particle accelerators, nuclear reactors, ion traps). Therefore, outside of specialized labs, we can say that as a good approximation radioactive decay half-lives don't change. For instance, carbon dating and geological radiometric dating are so accurate because decay half-lives in nature are so close to constant."

[Sherlock Holmes]

[Replying to Sherlock Holmes in post #43]

Note how gravitational time dilation is included, the same effect that must be compensated for in the atomic clocks used by the GPS system for example.

This is not a change in the actual radioactive decay rate, but in the measurement of it by an observer that is not traveling at the same high rate of speed as the decaying atoms. If you were traveling with the decaying atoms at their speed you would not measure a different decay rate. Since most radiometric dating is done using alpha or beta decay, and not electron capture, those small changes are not relevant. And no dating is done while travelling anywhere near speeds where time dilation would need to be considered. Also note the last paragraph of the article (underline mine):

"When reference books list values for the half-life of various materials, they are really listing the half-life for the material when its atoms are at rest, in the ground state, and in a particular chemical bonding configuration. Note that most changes to the half-life of radioactive materials are very small. Furthermore, large changes to a half-life require elaborate, expensive, high-energy equipment (e.g. particle accelerators, nuclear reactors, ion traps). Therefore, outside of specialized labs, we can say that as a good approximation radioactive decay half-lives don't change. For instance, carbon dating and geological radiometric dating are so accurate because decay half-lives in nature are so close to constant."

I'm not sure I agree. The decay rate is a function of the difference between the observer's frame of refence and the observed atoms. The difference in gravitational potential between an earth bound observer and the orbiting satellite means that the decay rate - as observed from earth - seems higher than for the same element observed locally on the earth.

This means that we (on earth) see a discrepancy of 45 uS/day, the orbiting clocks tick "faster" and gain 45 uS every 24 hours. One thing about relativity to bear in mind is that there is no longer is an "actual" anything, everything depends on the frame of reference of the observer relative to the observed and no frame of reference is special, two observers seeing different values for some observation are equally valid, there is no universal actual value.

Now I do understand how they measure decay rate, they measure them locally, at rest, that's not disputed, the point is the ratio of decayed to undecayed will be a function of not just the decay rate, but the materials history and if we don't know that history and how it affected the material we can't be be confident that the ratio reflects only the objects age.

[DrNoGods]

[Replying to Sherlock Holmes in post #46]

I'm not sure I agree. The decay rate is a function of the difference between the observer's frame of refence and the observed atoms. The difference in gravitational potential between an earth bound observer and the orbiting satellite means that the decay rate - as observed from earth - seems higher than for the same element observed locally on the earth.

I'm not disputing Relativity or time dilation, just pointing out that it isn't relevant to radiometric dating of things on Earth.

Now I do understand how they measure decay rate, they measure them locally, at rest, that's not disputed, the point is the ratio of decayed to undecayed will be a function of not just the decay rate, but the materials history and if we don't know that history and how it affected the material we can't be be confident that the ratio reflects only the objects age.

This is just another way of saying that radiometric dating depends on a constant rate of decay over time, which it does (along with other assumptions/corrections that might relate to the initial distribution of parent isotopes). The history of an object woud be more relevant to meteorite dating I'd think as those could have been (and likely were) whizzing around the solar system for millions or billions of years before impacting Earth. So I'd go back to the AIG articles linked in post #4. There is remarkably good agreement on ages using many different samples and many different isotopes among many research groups and their instrumentation. This suggests that changes in radioactive decay rates over time, if any, must be very small.

[Sherlock Holmes]

[Replying to Sherlock Holmes in post #46]

I'm not sure I agree. The decay rate is a function of the difference between the observer's frame of refence and the observed atoms. The difference in gravitational potential between an earth bound observer and the orbiting satellite means that the decay rate - as observed from earth - seems higher than for the same element observed locally on the earth.

I'm not disputing Relativity or time dilation, just pointing out that it isn't relevant to radiometric dating of things on Earth.

Now I do understand how they measure decay rate, they measure them locally, at rest, that's not disputed, the point is the ratio of decayed to undecayed will be a function of not just the decay rate, but the materials history and if we don't know that history and how it affected the material we can't be be confident that the ratio reflects only the objects age.

This is just another way of saying that radiometric dating depends on a constant rate of decay over time, which it does (along with other assumptions/corrections that might relate to the initial distribution of parent isotopes). The history of an object woud be more relevant to meteorite dating I'd think as those could have been (and likely were) whizzing around the solar system for millions or billions of years before impacting Earth. So I'd go back to the AIG articles linked in post #4. There is remarkably good agreement on ages using many different samples and many different isotopes among many research groups and their instrumentation. This suggests that changes in radioactive decay rates over time, if any, must be very small.

Well when I say the history of an "object" I meant a volume of C14, perhaps high in the atmosphere, this is borne out by the consideration I just found listed:

The variation in the 14 C/12 C ratio in different parts of the carbon exchange reservoir means that a straightforward calculation of the age of a sample based on the amount of 14 C it contains will often give an incorrect result. There are several other possible sources of error that need to be considered.

The errors are of four general types:

1. Variations in the 14 C/12 C ratio in the atmosphere, both geographically and over time.
2. Isotopic fractionation
3. Variations in the 14 C/12 C ratio in different parts of the reservoir
4. Contamination

From here.

As you can read, the ratio of atmospheric C12/C14 can be assumed to have been constant for thousands of year but it has not and this impacts the calculated age. I'm not making any quantitative claims here about the age of this or that, I'm just emphasizing that - qualitatively - the OP is right when he mentions that there are assumptions involved and different assumptions lead to different computed ages for things, not just carbon dating but potentially any radioactive based dating.

[Jose Fly]

Ahem......calibration.....it's a thing.

[DrNoGods]

[Replying to Sherlock Holmes in post #48]

Well when I say the history of an "object" I meant a volume of C14, perhaps high in the atmosphere, this is borne out by the consideration I just found listed:

Yes ... all of this has to be taken into consideration and is (including the impacts of nuclear testing in the mid 20th century, the reservior effect in shell carbonates, sample contamination, etc.). 14-C is only good for dating things up to about 50,000 years ago or less so is very limited and not used for fossils, rocks etc. that aren't very young. Other atoms and isotopes are used. Isochron methods were developed to help get around some of the parent issues and things that can alter those (remelting and mixing, etc.).

All of the factors have to be taken into account that could impact a measurement or interpretation for radiometric dating. The sheer number of measurements that have been accumulated over the decades, and the independent alternative methods for dating (post #9) that can confirm (or not) a radiometric measurement, all contribute to radiometric dating being an accepted method to ascertain the dates of things within the uncertainties that are always given for the measurements (some of which arise from uncertainty over the history, possible contamination levels, etc.). So far, significant variations in alpha/beta decay rates over time have not been demonstrated.