Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 79 (8898 total)
Current session began: 
Page Loaded: 03-26-2019 10:09 PM
20 online now:
Chatting now:  Chat room empty
Newest Member: WookieeB
Post Volume:
Total: 848,681 Year: 3,718/19,786 Month: 713/1,087 Week: 82/221 Day: 36/17 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Prev12
3
4Next
Author Topic:   Problems with Radiometric Dating?
PaulK
Member
Posts: 14754
Joined: 01-10-2003
Member Rating: 1.9


Message 31 of 46 (482798)
09-18-2008 1:59 AM
Reply to: Message 30 by eial
09-17-2008 9:58 PM


Re: Too many assumptions unless you convince otherwise
quote:

1. We must know how much radioactive material we have started with. Any slight amount has an exponential effect on the date. The formula is very basic

(1/2)n x massi = massf, where n= number of half lives. n is what we are trying to find, massf is what we know. We do not know massi, the mass we started with. We have to assume we know how much we start with. Could somebody please explain how we can tell, sitting here today, how much radioactive isotope we started with.


There are a number of techniques of using radioactivity to determine ages. You seem to be assuming a system like carbon dating where only the parent isotope is considered.
In the case of carbon dating specifically we do have good estimates for the initial mass (more accurately estimate of the proportion of radiocarbon to carbon).

Since this question has to be dealt with on the basis of specific methods, which others do you have in mind ?

quote:

2. There is no radioactive material that has moved in or out during or after the formation of the substance. During the formation, whether it is hundreds or millions of years, how in the world can we determine this.

Whether material can move in or out is determined by physics and chemistry. By choosing samples where it would be very difficult or impossible for the relevant material to move in or out this problem can be avoided.

quote:

3. That the rate of decay is constant. Well, if you measure the decay rate for say, 1 year, or even a 100 years, and determine the decay rate to be 4 million years, this is an extreme extrapolation, especially for an exponential equation.

That would make sense if we had no understanding of how radioactive decay worked, so that all we had were measurements. However that is not the case. Changing the decay rate would involve making serious alterations to the way matter works. We have no reason to believe that that is even a remote possibility under the conditions we have to consider and evidence that it has not happened.

quote:

This is absurd, I can’t believe this is even discussed, there are just too many variables. Radiometric dating is an unreliable source for dating inorganic material. And don’t skirt around the issue and say that I got this off some of the many creationist websites out there and therefore it is somehow invalid.

Now hold on a minute. Don't you think that if radiometric dating were really that obviously flawed the experts wouldn't know about it ? And that if it was that flawed they wouldn't use it ? Isn't what you are suggesting absurd ?


This message is a reply to:
 Message 30 by eial, posted 09-17-2008 9:58 PM eial has not yet responded

Replies to this message:
 Message 32 by Coyote, posted 09-18-2008 5:45 PM PaulK has not yet responded

    
Coyote
Member (Idle past 187 days)
Posts: 6117
Joined: 01-12-2008


Message 32 of 46 (482892)
09-18-2008 5:45 PM
Reply to: Message 31 by PaulK
09-18-2008 1:59 AM


Re: Too many assumptions unless you convince otherwise
You [Elal, not PaulK] seem to be falling into the standard creationist trap that "assumption" equals "wrong."

I deal a lot with radiocarbon dating, and I would be happy to explain some of these things to you. There are also others here who are quite familiar with the technique who can help.

But please, don't even bother with the standard creationist talking points. They are worthless. Come up with real questions and we'll do the best we can to help you with the answers.

Edited by Coyote, : No reason given.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
This message is a reply to:
 Message 31 by PaulK, posted 09-18-2008 1:59 AM PaulK has not yet responded

  
RAZD
Member
Posts: 19759
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 7.1


Message 33 of 46 (482912)
09-18-2008 7:23 PM
Reply to: Message 30 by eial
09-17-2008 9:58 PM


Re: Too many assumptions unless you convince otherwise
Welcome to the fray, eial.

Radiometric dating cannot be PROVEN to be reliable, especially in dating inorganic material, there are too many assumptions.

Actually it can be proven to be very reliable. This is done by three different methods:


  • one is to repeat dating tests with several different tests from the same sample and seeing how "clustered" the results are. Repeat these tests with a different age samples. When these results are within a few percentage points of each other for each of the different age samples this shows that the method does not have variable results, so these results are reliably replicated.
  • second is to repeat dating tests using several different methods on the same sample and seeing how "clustered" these results are. Repeat these tests with a different age samples. When these results are within a few percentage points of each other this shows that each of the methods do not have different results, nor do they give different ages for different age samples, so these results are reliably replicated.
  • third is to compare the ages derived from this testing with other methods for measuring age that don't rely on radioactive decay.

Here is a graph of one such correlation between radiometric dating and actual age:


Click to enlarge

The formula is very basic

(1/2)n x massi = massf, where n= number of half lives. n is what we are trying to find, massf is what we know. We do not know massi, the mass we started with. We have to assume we know how much we start with. Could somebody please explain how we can tell, sitting here today, how much radioactive isotope we started with.

If you type mass<sub>f</sub> = mass<sub>i</sub>*(1/2)<sup>n</sup>
then it displays massf = massi*(1/2)n

With parent daughter systems you can estimate the amount that has decayed by the amount of daughter mass to the remaining parent mass.

With radiocarbon we can estimate the amount from the amount in the atmosphere today as a first approximation. We can also find correlations that tell us the actual age of objects and then use that to calculate the actual amount of carbon-14 in the atmosphere at different times, and once that correlation is known we can then calculate more accurate ages from samples. This graph shows the results of precisely that process:


Click to enlarge

This extends the correlation from the first graph out to the practical limit for radiocarbon dating (~45k years), where the green line is the part shown above.

See Age Correlations for more examples of correlations between different methods of measuring age, and for different ways to validate the reliability of radioactive dating.

3. That the rate of decay is constant. Well, if you measure the decay rate for say, 1 year, or even a 100 years, and determine the decay rate to be 4 million years, this is an extreme extrapolation, especially for an exponential equation.

What you can look at is evidence that it has not changed. This comes from stars, where you can see the same radioactive decay for the same isotopes as we see today, yet the light is millions of years old ...

... and this comes from simple events here on earth:

uranium halos can only be made by hundreds of millions of years of uranium decay with a constant decay rate - changing the decay rate would change the alpha particle energy and change the radius of the halo, so the existence of uranium halos is evidence that decay rates have not changed for hundreds of millions of years.

Prehistoric natural reactors show exactly the same process of nuclear reaction that we see in modern reactors, again demonstrating that decay rates have not changed since they occurred, 2000 million years ago.

Enjoy.

ps - since you are new, some posting tips:

type [qs]quotes are easy[/qs] and it becomes:

quotes are easy

or type [quote]quotes are easy[/quote] and it becomes:

quote:
quotes are easy

also check out (help) links on any formating questions when in the reply window.

For other formating tips see Posting Tips

Edited by Admin, : Reduce width of too-wide images.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 30 by eial, posted 09-17-2008 9:58 PM eial has responded

Replies to this message:
 Message 34 by Coyote, posted 09-18-2008 7:53 PM RAZD has acknowledged this reply
 Message 41 by eial, posted 09-22-2008 11:57 PM RAZD has responded

  
Coyote
Member (Idle past 187 days)
Posts: 6117
Joined: 01-12-2008


Message 34 of 46 (482915)
09-18-2008 7:53 PM
Reply to: Message 33 by RAZD
09-18-2008 7:23 PM


Re: Too many assumptions unless you convince otherwise
Good post.

Let's see if we get anything intelligent back, or just the usual AnswersinGenesis talking points. (Refuting those gets to be so boring after the first few dozen times.)


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
This message is a reply to:
 Message 33 by RAZD, posted 09-18-2008 7:23 PM RAZD has acknowledged this reply

  
JonF
Member
Posts: 4487
Joined: 06-23-2003
Member Rating: 3.0


Message 35 of 46 (482920)
09-18-2008 8:25 PM
Reply to: Message 30 by eial
09-17-2008 9:58 PM


Re: Too many assumptions unless you convince otherwise
I always find it incredible that people who know absolutely nothing about radiometric dating, but are willing to swallow the falsehoods promuloated by other ignorant (or lying) people, are so eager to post on message boards and reveal exactly how little they know.

1. We must know how much radioactive material we have started with.

Not even close. In geological dating, the original amount of radioactive material does not enter into the dating equation(s). It's irrelevant. You mean "We must know how much daughter isotope material we have started with". That is true &hellp; but there is lots of information available that can tell us the amount. Isochron methods use the chemical/mechanical identity of various isotopes of the daughter product to produce the initial quantity of daughter product as a result of the anlysis, not a premise. The most widely used method, U-Pb concordia-discordia, is applied to materials (mostly zircons) that just don't incorporate any significant amount of daughter material at solidification … even if the solidifying zircon is immersed in a sea of molten lead. (A fact which, BTW, was explicitly recognized by the RATE group). The widely used Ar-Ar method is similar to isochron methods in that it is not affected by any premises about the amount of initial daughter. The K-Ar method, beloved of creationists because it is possible for it to be fooled but not used much anymore, relies on the premise that the gaseous daughter product escaped from the liquid melt. Rational sample selection (e.g. avoiding the situations in which this is known to be problematic) almost always leads to reliable dates, and shown by the excellent agreement of K-Ar dates with more robust methods. Irrational and fraudulent sample selection, often practiced by creationists, can produce obviously false results; but this is a problem with creationists, not with the method.

2. There is no radioactive material that has moved in or out during or after the formation of the substance.

Again a mis-statement. You mean "There is no relevant material that has moved in or out during or after the formation of the substance." Daughter product moving in or out could be (but is not) a problem.

During the formation, whether it is hundreds or millions of years, how in the world can we determine this.

If you made the effort to actually learn something about radiometric dating, you would know exactly how in the world we determine this. It's quite clever. Isochron, U-Pb, and Ar-Ar methods essentially always indicate as a result of the analysis whether or not relevant material has been gained or lost. And Ar-Ar and U-Pb methods can often produce a reliable date even when relevant material has been gained or lost!

3. That the rate of decay is constant. Well, if you measure the decay rate for say, 1 year, or even a 100 years, and determine the decay rate to be 4 million years, this is an extreme extrapolation, especially for an exponential equation.

Well, you finally got one right (although "4 million years" is not a decay rate or any kind of rate). Did you bother to do the analysis of how much an error in radioactive decay rates would affect dating? Real scientists have. The uncertainty in dates due to uncertainty in decay rates is a percent or two, not the several orders of magnitude you're looking for.

Of course, what you are looking for is a gigantic change in decay rates in the past. Alas for you, there are three wildly different mechanisms that are called radioactive decay. It's pretty much unthinkable that they would change in exactly the concerted manner required to maintain the agreement between different dating methods. Of course, it's possible. But, again alas for you, these mechanisms also involve very fundamental physical processes and any change in them would have widespread and easily detectable consequences. We've looked of lots of these consequences. They aren't there. The rates of radioactive decay has been constant within much less than a percent for 13-ish billion years. For example, see The Constancy of Constants and The Constancy of Constants, Part 2

Radiometric dating is an unreliable source for dating inorganic material. And don’t skirt around the issue and say that I got this off some of the many creationist websites out there and therefore it is somehow invalid. Give me the information, I am into some real, evidence that this is a valid source for dating.

Of course you got it off some creationist website, that's the only source for such erroneous information. It's not erroneous because you got it off some creationist website, it's erroneous because it is based on multiple fundamental misunderstandings of the methods of radiometric dating.

There'a alot you need to learn before you are prepared to critique radiometric dating, and a discussion board is a terrible medium for teaching the subject. But I'll give you some pointers.

In the unlikely event that you want to learn about radiometric dating, Radiometric Dating: A Christian Perspective is a very good place to start. The Age of the Earth is excellent, covering all major methods well. Isochron Dating is a bit more advanced. The U-Th-Pb system: zircon dating is definitely advanced material, but I don't know of a better web reference on U-Pb dating.


This message is a reply to:
 Message 30 by eial, posted 09-17-2008 9:58 PM eial has not yet responded

  
Chiroptera
Member (Idle past 17 days)
Posts: 6531
From: Oklahoma
Joined: 09-28-2003


Message 36 of 46 (482975)
09-19-2008 10:53 AM
Reply to: Message 30 by eial
09-17-2008 9:58 PM


Too many assumptions -- yet it works!
And, despite all the possible misgivings, radiometric dating actually works!

The geologic time scale was already worked out by geologists long before radioactivity was discovered. All radiometric dating has done is give us actual absolute dates, whereas before all they had were relative dates (these rocks are older than those rocks).

When radiometric dating was first done, the dates were consistent with the already known geologic time scale. If radiometric dates were subject to arbitrary errors, we would expect that the dates would be inconsistent with the geologic time scale. Formations that were known to be older than other formations might have been radio-dated as younger -- yet this hasn't happened.

Further, radiometric dating uses different radioactive materials that produces different daughter isotopes that are found in different crystals. If such things as initial amounts of materials and/or rates at which material escapes or is added to the crystal were a problem, it would cause different amounts of errors for all the different techniques. Therefore, different radiometric techniques should give wildly different dates for the same formation.

Yet, this doesn't happen either. Different techniques give the same ages for the same formations.

So these possible errors, although they might potentially be a problem, are seen to be no problem at all.

As far as the rate of decay being constant: we understand very well the physics behind radioactive decay. If decay rates were different in the past, then we know which laws of physics would have been different in the past. Then we can tell what other things should be seen in the archeological/geologic record. For example, other elements that would normally be stable would have been radioactive as well, and we can tell which ones would have been radioactive, and what the daughter isotopes would have been, and we can then check whether we see this different radioactive phenomenon. But we don't see these things.

So we can conclude that radioactive decay rates have essentially been the same over the time scales that we are observing.

One other thing, is that there are two forms of radioactive decay that we observe that are relevant to dating: alpha decay and beta decay. These two types are governed by different laws of physics. There is no reason to suspect that they would have been different in the past by exactly the same amounts. Thus, two different dating techniques relying on these different types of decay modes should, as before, produce different ages for the same formations. Yet they don't. All techniques give essentially the same ages.

Again, the test on whether our assumptions are reliable is to see whether the dating actually works. And it does.


Speaking personally, I find few things more awesome than contemplating this vast and majestic process of evolution, the ebb and flow of successive biotas through geological time. Creationists and others who cannot for ideological or religious reasons accept the fact of evolution miss out a great deal, and are left with a claustrophobic little universe in which nothing happens and nothing changes.
-- M. Alan Kazlev
This message is a reply to:
 Message 30 by eial, posted 09-17-2008 9:58 PM eial has not yet responded

Replies to this message:
 Message 37 by armylngst, posted 09-20-2008 1:29 PM Chiroptera has responded

  
armylngst
Junior Member (Idle past 3749 days)
Posts: 2
Joined: 09-20-2008


Message 37 of 46 (483168)
09-20-2008 1:29 PM
Reply to: Message 36 by Chiroptera
09-19-2008 10:53 AM


Re: Too many assumptions -- yet it works!
I have a question (and it may not sound to scientific since I am not a scientist, but this does bother me). How do scientists know how much radioactive materials that decay was present at the creation (by big bang, by God, by whatever) of the universe next to their byproducts? (That is not to say that the byproducts present came from radioactive decay, just that they match up and an ignorant observer (someone not present at the creation of the universe) could mistake for something that came from radioactive decay.)

NOTE: I do not speak about the present, I speak only about the creation of the universe. In the same way, what about the creation (by whatever means) of the planet earth? Do scientists know exactly what the dispersal of radioactive materials to their counterparts were when the earth came into being? (Once again I do not speak of the creation of rocks and the dispersion of radioactive materials and their decayed counterparts.)


This message is a reply to:
 Message 36 by Chiroptera, posted 09-19-2008 10:53 AM Chiroptera has responded

Replies to this message:
 Message 38 by Coyote, posted 09-20-2008 2:13 PM armylngst has not yet responded
 Message 39 by RAZD, posted 09-20-2008 2:18 PM armylngst has not yet responded
 Message 40 by Chiroptera, posted 09-20-2008 2:50 PM armylngst has not yet responded

    
Coyote
Member (Idle past 187 days)
Posts: 6117
Joined: 01-12-2008


Message 38 of 46 (483175)
09-20-2008 2:13 PM
Reply to: Message 37 by armylngst
09-20-2008 1:29 PM


Re: Too many assumptions -- yet it works!
I will let others answer your questions on the other forms of radiometric dating; I will take a shot at radiocarbon dating, as that's the one I am most familiar with.

Carbon 14 or radiocarbon is formed in the atmosphere by cosmic rays. We can measure the current amounts of radiocarbon in the atmosphere, and through radiocarbon dating of tree rings we can determine how those amounts have fluctuated in the past. This results in a calibration curve to correct for the small atmospheric fluctuations that have occurred.

The decay of C14 occurs at a known rate, so the amount remaining can be compared to the beginning amount to determine age.

There are other factors that need to be considered, but that is the short answer on how we know the beginning amounts for C14.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
This message is a reply to:
 Message 37 by armylngst, posted 09-20-2008 1:29 PM armylngst has not yet responded

  
RAZD
Member
Posts: 19759
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 7.1


Message 39 of 46 (483176)
09-20-2008 2:18 PM
Reply to: Message 37 by armylngst
09-20-2008 1:29 PM


Re: Too many assumptions -- yet it works!
Welcome to the fray armylngst,

How do scientists know how much radioactive materials that decay was present at the creation (by big bang, by God, by whatever) of the universe next to their byproducts?

This would be a great new topic. My answer would be ... none. No radioactive materials, because they had not formed yet in the bellies of stars by fusion of the Helium that predominated in the early universe.

Go to Forum Proposed New Topics to post new topics.

Enjoy.



ps - as you are new, some tips

type [qs]quotes are easy[/qs] and it becomes:

quotes are easy

type [qs]quotes are easy[/qs] and it becomes:

quotes are easy

or type [quote]quotes are easy[/quote] and it becomes:

quote:
quotes are easy

also check out (help) links on any formating questions when in the reply window.

For other formating tips see Posting Tips

type: [url=http://insert_your_url_here]this message is linked to an url[/url]
and it becomes: this message is linked to an url (one with even more posting tips).

And if you use the other reply buttons (there's one at the bottom right of each message):


... your message is linked to the one you are replying to (adds
clarity). You can also look at the way a post is formated with the "peek" button next to it.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 37 by armylngst, posted 09-20-2008 1:29 PM armylngst has not yet responded

  
Chiroptera
Member (Idle past 17 days)
Posts: 6531
From: Oklahoma
Joined: 09-28-2003


Message 40 of 46 (483178)
09-20-2008 2:50 PM
Reply to: Message 37 by armylngst
09-20-2008 1:29 PM


Re: Too many assumptions -- yet it works!
How do scientists know how much radioactive materials that decay was present at the creation (by big bang, by God, by whatever) of the universe next to their byproducts?

I'll give a very short (and perhaps inaccurate) reply until someone more knowledgeable comes along.

In regards to using radioisotopes to date geologic materials, it isn't necessary to know how much stuff formed during the Big Bang. The radiometric date relies on knowing how much of the materials were present in the solid crystals in the rocks when they first solidified from the melt.

When a crystal forms, a certain radioisotope will be trapped in the crystal structure. As it decays, it will turn into a certain daughter isotope. At the beginning, there will parent isotope and no daughter isotope. As time goes one, parent atoms will disappear and daughter atoms will appear, so the ratio of daughter to parent will increase from zero to some value that depends on the age of the rock. The more daughter isotope compared to parent, the older the rock.

One doesn't need to know exactly how much parent was present initially, since all one needs to know is the relative amount of parent compared to daughter. And one can usually assume that there is was no daughter present (or such a miniscule amount that it doesn't affect the age determination much) initially since the known physics and chemistry of the formation of the crystal from the melt allows scientists to determine that none or very, very little daughter should become trapped in the crystal as if forms.

Again, we can be fairly certain that these assumptions are good since different dating techniques relying on different isotopes in different crystals which have different structures give the same ages for the same rocks, and that these dates are consistent with what geologists knew about the ages before radioactivity was discovered. If scientists were wrong about the initial amounts of parent and daughter, or were wrong about how much parent and daughter might travel into or out of the crystal over time, then the differing amounts of parent and daughter and the different travelling abilities would cause the different dating techniques to give wildly different ages for the same materials.

Finally, there are dating techniques that do not rely on making any assumptions about the initial amounts of the materials at all. Isochron dating is an important dating method that does not rely on any assumptions about the initial amounts of isotopes in the crystals.

-

How do scientists know how much radioactive materials that decay was present at the creation (by big bang, by God, by whatever) of the universe next to their byproducts?

Now, if you are interested in the Big Bang, scientists are able to determine the relative abundances by apply the laws of thermodynamics to the physical conditions that occurred when atoms were first able to form. There was a time when the universe was so hot and so dense that protons and neutrons could not stay together to form stable atomic nuclei. As the universe expanded and cooled, there was a time when the protons and neutrons could stick together and stay together as atomic nuclei. Apply the laws of thermodynamics to knowledge of how the forces that hold nuclei together operate, they have been able to determine that all that formed during the Big Bang were hydrogen and helium, with some trace amounts of lithium (and maybe some beryllium -- my memory is hazy about this).

All the other elements were mostly formed in the cores of large stars and then scattered in the universe when the stars exploded in super novae.

-

Do scientists know exactly what the dispersal of radioactive materials to their counterparts were when the earth came into being?

I don't know how exact the knowledge is, but scientists can observe the present amounts of radioactive isotopes and their daughter isotopes, and work backwards to figure out how much of each isotope was present 4.5 billion years ago.

Also, as Lord Kelvin pointed out about a century ago, the interior of the earth should be much cooler than it is now. Assuming that the extra heat came from radioactive decay, they can figure out how much decay there was. By looking at the relative abundances that exist today, as well as the ability of denser crystals and materials to sink into the interior during the molten phase of the earth's history, they can get some estimates as to the abundances of the various radioactive materials. I don't know how accurate these abundances are, though.


Speaking personally, I find few things more awesome than contemplating this vast and majestic process of evolution, the ebb and flow of successive biotas through geological time. Creationists and others who cannot for ideological or religious reasons accept the fact of evolution miss out a great deal, and are left with a claustrophobic little universe in which nothing happens and nothing changes.
-- M. Alan Kazlev
This message is a reply to:
 Message 37 by armylngst, posted 09-20-2008 1:29 PM armylngst has not yet responded

  
eial
Junior Member (Idle past 3725 days)
Posts: 6
From: Medford, Oregon US
Joined: 09-08-2008


Message 41 of 46 (483530)
09-22-2008 11:57 PM
Reply to: Message 33 by RAZD
09-18-2008 7:23 PM


Re: Too many assumptions unless you convince otherwise
RAZD,

I agree, with coyote, good post, thanks for the info. I think the idea of “calibrating” C14 with tree rings is great. Yet, I see a couple of problems here. First of all, tree rings are not always annual. So, we have to assume these are annual rings, I am assuming for the most part they are, but over a long period (say thousands of years), a few extra rings here and there could give an older date for the tree. Just a thought, I am not willing to die on this mountain. Correct me if I am mistaken, but the oldest trees I have been able to find, based on their rings alone, have been in the 4500 range. It is interesting that as you look at the graph, and just for kicks, drop the 5K and beyond, the graph appears to start a significant divergent from the linear path it appears to be taking.
With parent daughter systems you can estimate the amount that has decayed by the amount of daughter mass to the remaining parent mass.
Again, an assumption has to be made that all the “daughter” mass actually is daughter mass (came from the parent isotope), and was not already present in the sample. This is a very large assumption, especially since the consequence of being off could mean the difference in millions of years versus tens of thousands. How this estimation can be done with any accuracy is beyond me.

With radiocarbon we can estimate the amount from the amount in the atmosphere today as a first approximation. We can also find correlations that tell us the actual age of objects and then use that to calculate the actual amount of carbon-14 in the atmosphere at different times, and once that correlation is known we can then calculate more accurate ages from samples.

What correlations are you referring to that tell us the actual age of objects that goes beyond say, 5K years? If we have correlations that tell us actual object ages, why are we even belaboring the issue of radioactive dating? We must know what these calibrations are, and see how many assumptions there are in these. If we are not accurate with our calibration tools, calibrating against an inaccurate instrument is useless. This sounds like we are getting somewhere.

By the way, I sure appreciate the tips on posting. We will see if I have learned any posting etiquette.


This message is a reply to:
 Message 33 by RAZD, posted 09-18-2008 7:23 PM RAZD has responded

Replies to this message:
 Message 42 by Coyote, posted 09-23-2008 12:11 AM eial has not yet responded
 Message 43 by Coragyps, posted 09-23-2008 12:30 AM eial has not yet responded
 Message 44 by NosyNed, posted 09-23-2008 12:43 AM eial has not yet responded
 Message 45 by JonF, posted 09-23-2008 8:03 AM eial has not yet responded
 Message 46 by RAZD, posted 09-23-2008 8:29 PM eial has not yet responded

  
Coyote
Member (Idle past 187 days)
Posts: 6117
Joined: 01-12-2008


Message 42 of 46 (483531)
09-23-2008 12:11 AM
Reply to: Message 41 by eial
09-22-2008 11:57 PM


Re: Too many assumptions unless you convince otherwise
A couple of explanations:

The "annualness" of tree rings can be correlated by comparing tree rings with volcanic activities of known dates. You've heard of the "year with no summer" and other such historical events; they look for these in the tree rings as one method of determining whether more than one ring is produced per year. If you find the eruption of 1601 or 1602 accurately portrayed in the rings, you have helped confirm the reliability of the method.

Some trees do produce more than one ring. The primary ones used for the US calibration curve are the bristlecone pines found in the White Mountains of southern California. They are very stable.

And they extend far older than 5,000 years. By matching up ring patterns in living trees with those from standing dead trees they have exceeded 12,000 years.

Other such information comes from oaks in Europe, corals, glacial varves etc.

The daughter product in radiocarbon dating is not important, as it is not measured. What is measured is the residual C14. And the initial amount is what is established by comparison with the tree rings. If you date a series of rings, say, 9,670 years in age you can establish the degree of correction at that point. This takes care of atmospheric fluctuations.

Radiocarbon dating is only used back some 50 or 60,000 years. The millions of years would be other forms of radiometric dating.

Hope this helps.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
This message is a reply to:
 Message 41 by eial, posted 09-22-2008 11:57 PM eial has not yet responded

  
Coragyps
Member
Posts: 5377
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 43 of 46 (483533)
09-23-2008 12:30 AM
Reply to: Message 41 by eial
09-22-2008 11:57 PM


Re: Too many assumptions unless you convince otherwise
What correlations are you referring to that tell us the actual age of objects that goes beyond say, 5K years? If we have correlations that tell us actual object ages, why are we even belaboring the issue of radioactive dating?

In the case of carbon-14, there are a bunch in addition to tree rings from several sites: annual varves in lake bottoms and in the seafloor, annual layers in ice in Greenland, Antarctica, and on top of most of the high mountain ranges in the world, uranium-thorium dating on corals and on stalagmites....and they all match up pretty nicely, showing the "wiggles" one would expect from the variations in Earth's changing tilt and orbital variations. It's pretty interesting stuff.

Oh....and radiocarbon dating is useful anywhere you find old carbon. That's a LOT more places than you can find stalagmites.

Edited by Coragyps, : No reason given.


This message is a reply to:
 Message 41 by eial, posted 09-22-2008 11:57 PM eial has not yet responded

    
NosyNed
Member
Posts: 8839
From: Canada
Joined: 04-04-2003
Member Rating: 2.9


Message 44 of 46 (483535)
09-23-2008 12:43 AM
Reply to: Message 41 by eial
09-22-2008 11:57 PM


Calibration and Correlation
So, we have to assume these are annual rings, I am assuming for the most part they are, but over a long period (say thousands of years), a few extra rings here and there could give an older date for the tree.

But, you see, this method of calibration shows that, if there are any extra rings -- that are not detected (and it is possible to see them) or any missing rings (which can occur) doing a comparison of radiocarbon dates to tree ring counts shows that, at worst, the erroneous ring count can't be too far out -- that is less than the 10 % that the variations in C14 content can produce. If there were many extra rings (say) scattered in the tree we'd get a ring count that is too old and there would not be any kind of good match between the C14 date and ring date.

E.g., Let's say there are twice as many rings as years.

That means that the "ring year" line would be twice as steep as the "real year" line on a graph.
(see Message 1 for an example of years from varve counting (like tree rings in behavior)

So if that were the case and we plotted C14 age against this where would the C14 line run?

There are lots of cases:
1) It could be utterly random. If the C14 in the atmosphere was changing drammatically year to year this might be the result.
2) It could match (more or less) the "real years" which is the hypothosis we started with. In this case it would be half as steep as the "ring years" line and very far from it pretty quickly. But if C14 decays as both the mathematics and tests say it does then it would still fall on a line and not be random.
3) It could match the false "ring years". This would happen if C14 decayed just about twice as fast as we have measured it to do. How likely is it that it would be measured wrong by just enough to match the mismeasure in the ring count?

What we see (as in the linked example) is that the C14 date more or less (around 10% variance) the counted date.

Not only that, it does it for many different trees, of different kinds, in different climates and in different places. There seems to be no possible explanation for these matches other than that both the C14 measurements and the tree ring counts are both tracking pretty close to the actual correct years. Can you think of another one?

Again, an assumption has to be made that all the “daughter” mass actually is daughter mass (came from the parent isotope), and was not already present in the sample.

This has nothing to do with C14 dating. In C14 dating we are measuring what we might call the "parent". Other forms of dating measure ratios of parents to daughters. It is not an issue here.

How this estimation can be done with any accuracy is beyond me.

It may be beyond you but in fact this can be checked in a number of ways. It is not a problem for the majority of dating tests.


This message is a reply to:
 Message 41 by eial, posted 09-22-2008 11:57 PM eial has not yet responded

  
JonF
Member
Posts: 4487
Joined: 06-23-2003
Member Rating: 3.0


Message 45 of 46 (483558)
09-23-2008 8:03 AM
Reply to: Message 41 by eial
09-22-2008 11:57 PM


Re: Too many assumptions unless you convince otherwise
Again, an assumption has to be made that all the “daughter” mass actually is daughter mass (came from the parent isotope), and was not already present in the sample.

This is not true for the vast majority of geological dates. You should have read message 35, just above:

quote:
…there is lots of information available that can tell us the amount. Isochron methods use the chemical/mechanical identity of various isotopes of the daughter product to produce the initial quantity of daughter product as a result of the analysis, not a premise. The most widely used method, U-Pb concordia-discordia, is applied to materials (mostly zircons) that just don't incorporate any significant amount of daughter material at solidification … even if the solidifying zircon is immersed in a sea of molten lead. (A fact which, BTW, was explicitly recognized by the RATE group). The widely used Ar-Ar method is similar to isochron methods in that it is not affected by any premises about the amount of initial daughter. The K-Ar method, beloved of creationists because it is possible for it to be fooled but not used much anymore, relies on the premise that the gaseous daughter product escaped from the liquid melt. Rational sample selection (e.g. avoiding the situations in which this is known to be problematic) almost always leads to reliable dates, and shown by the excellent agreement of K-Ar dates with more robust methods. Irrational and fraudulent sample selection, often practiced by creationists, can produce obviously false results; but this is a problem with creationists, not with the method.

How this estimation can be done with any accuracy is beyond me

It's not an estimate. To reinforce what Ned wrote, your ignorance of how it's done is not an indicator that it can't be done.

What correlations are you referring to that tell us the actual age of objects that goes beyond say, 5K years?

The major one is correlations between methods. We know what can affect different methods, and what affects method A may not affect method B. SO if we measure an age by methods A, B, and C, and each method is not affected by what might affect the others, and the three methods produce the same result, we have a good date.

And, of course, we have lots of evidence that the fundamental physics of the universe have been the same for a very long time. The only way that the hundreds of thousands, perhaps millions, of radiometric dates could all be wrong is to make tremendous changes in the fundamental physics of the Universe, including lots of tremendous changes required to hide the original change from what we see today. IOW, a gigantic series of miracles (another fact that the RATE group acknowledges). If there is indeed a God, He could have done that, but it simultaneously makes him a trickster God (which is a problem for most believers) and removes the question from the purview of science.


This message is a reply to:
 Message 41 by eial, posted 09-22-2008 11:57 PM eial has not yet responded

  
Prev12
3
4Next
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019