|
Register | Sign In |
|
QuickSearch
Thread ▼ Details |
|
Thread Info
|
|
|
Author | Topic: Assumptions involved in scientific dating | |||||||||||||||||||||||||||||||||||||||||||||||
DOCJ Inactive Member |
What is the formula used to determine the age of materials? And what are the constant variables?
ThanksDOCJ
|
|||||||||||||||||||||||||||||||||||||||||||||||
Coyote Member (Idle past 2132 days) Posts: 6117 Joined: |
What is the formula used to determine the age of materials? And what are the constant variables? Different materials are aged using different techniques. For example, radiocarbon dating works with materials containing carbon and has an upper limit of about 50,000 years. For other materials and older samples other dating methods are needed. RAZD has an excellent thread outlining many of these different methods and the very high correspondence between the different dating methods. As for the formula, all of my books on radiocarbon dating are at the office. The basic method is to detect the levels of C14, which decays at a known rate. That figure, "percent modern" can then be equated to calendar years. Corrections are necessary for isotopic fractionation and calibration is needed to adjust for atmospheric variation. A lot of details are spread throughout this thread, so take a few minutes to scan previous posts. Hope this helps.Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge. Belief gets in the way of learning--Robert A. Heinlein In the name of diversity, college student demands to be kept in ignorance of the culture that made diversity a value--StultisTheFool It's not what we don't know that hurts, it's what we know that ain't so--Will Rogers If I am entitled to something, someone else is obliged to pay--Jerry Pournelle If a religion's teachings are true, then it should have nothing to fear from science...--dwise1 "Multiculturalism" demands that the US be tolerant of everything except its own past, culture, traditions, and identity. Liberals claim to want to give a hearing to other views, but then are shocked and offended to discover that there are other points of view--William F. Buckley Jr.
|
|||||||||||||||||||||||||||||||||||||||||||||||
RAZD Member (Idle past 1431 days) Posts: 20714 From: the other end of the sidewalk Joined:
|
What is the formula used to determine the age of materials? ... I'll presume you mean the formula to determine the 14-C age of organic materials.
quote: Now I will note that 5568 is not that accurate for the half-life of 14-C: the current value is listed as 5,730 40 years (wiki), so a more accurate age would be older than this CRA, however the CRA needs to be corrected anyway due to the variation in 14-C content in the atmosphere from year to year, because it is not constant as assumed. As Coyote noted in Message 1 this correction is done by comparison to CRA values for samples of known age -- tree rings, lake and marine varves, etc. and this calibration also incorporates the correction for the half life. This correction in detailed in 14C Calibration and Correlations and the calibration curves for tree rings and varves are
As you can easily see the actual calibrated ages are consistently older than the straight line CRA age. Enjoyby 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)
|
|||||||||||||||||||||||||||||||||||||||||||||||
Coyote Member (Idle past 2132 days) Posts: 6117 Joined:
|
Thank, RAZD, for filling in those details.
Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge. Belief gets in the way of learning--Robert A. Heinlein In the name of diversity, college student demands to be kept in ignorance of the culture that made diversity a value--StultisTheFool It's not what we don't know that hurts, it's what we know that ain't so--Will Rogers If I am entitled to something, someone else is obliged to pay--Jerry Pournelle If a religion's teachings are true, then it should have nothing to fear from science...--dwise1 "Multiculturalism" demands that the US be tolerant of everything except its own past, culture, traditions, and identity. Liberals claim to want to give a hearing to other views, but then are shocked and offended to discover that there are other points of view--William F. Buckley Jr.
|
|||||||||||||||||||||||||||||||||||||||||||||||
Percy Member Posts: 22493 From: New Hampshire Joined: Member Rating: 4.9
|
DOCJ writes: What is the formula used to determine the age of materials? And what are the constant variables? It would be a good idea to check out the reference Coyote provides first: Answers to Creationist Attacks on Carbon-14 Dating. While the general concepts are simple, the specifics of the calculation have some details that require some explanation. I'll just quote from the Wikipedia article on Radiocarbon Datin:
quote: AbE: This seems to duplicate RAZD's information in Message 63. I actually typed up this message a few hours ago but didn't have a chance to proof it before I left, so when I returned I just proofed it and posted it, and only then did I notice RAZD's post. --Percy Edited by Percy, : AbE.
|
|||||||||||||||||||||||||||||||||||||||||||||||
DOCJ Inactive Member |
What assumptions are geologists making when dating rocks, etc? I'm wanting to find out the issues. It's just a matter of if one of you are going to provide them. I'm looking at the information and a few of the assumptions I'm seeing are how much daughter product was in the sample, how much parent was in the sample, that their model of gravitational physics is true, and I'm sure there are some inside the formula such as constant variables..
Thanks for all the information. Edited by DOCJ, : 😊
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1732 days) Posts: 4696 From: Colorado, USA Joined:
|
What assumptions are geologists making when dating rocks, etc?
It's really pretty simple. The assumptions are the the system is closed, the original isotopic composition can be estimated, the decay rates have been very nearly constant, that we can accurately measure the isotopes and that we can do the math correctly. I assume here that you are talking about radiometric dating.
I'm wanting to find out the issues.
I'm sure you are. This is the typical YEC procedure: find some feature that is not satisfactory to their absolutist approach and attack that point. In other words, they want absolute proof of constant decay rates or absolute certainty of original daughter elements even though most geochronologists are pretty much comfortable with the assumptions. Any doubt, no matter how unrelated, insignificant or mitigated, is precious to them. There are a number of tests for the reasonableness of the assumptions, but the typical forum YEC will simply ignore that fact.
It's just a matter of if one of you are going to provide them. I'm looking at the information and a few of the assumptions I'm seeing are how much daughter product was in the sample, how much parent was in the sample, that their model of gravitational physics is true, and I'm sure there are some inside the formula such as constant variables..
Well for one, I'm not sure what a 'constant variable' is. A really great thing would be for you, in good faith, to tell us the issues with your own method of dating geological events and then we could have a real discussion about the relative merits. Edited by edge, : No reason given.
|
|||||||||||||||||||||||||||||||||||||||||||||||
LamarkNewAge Member Posts: 2422 Joined: Member Rating: 1.2 |
There were some dating problems with Volcanic ash, right?
I was trying to find a link on the issue. This is one I found http://www.turkanabasin.org/...bones-and-rocks-of-contention plus this book covered the issue
quote: Here is a concern that Creationists often raise. Amazon review snip
quote: Put this keyword into Google kbs tuff origin of man bones of contention Any, this is the sort of thing that concerns creationists. Let questions be asked. Don't worry so much about the theological motivation. Just worry about the answers.
|
|||||||||||||||||||||||||||||||||||||||||||||||
RAZD Member (Idle past 1431 days) Posts: 20714 From: the other end of the sidewalk Joined: |
What assumptions are geologists making when dating rocks, etc? I'm wanting to find out the issues. It's just a matter of if one of you are going to provide them. I'm looking at the information and a few of the assumptions I'm seeing are how much daughter product was in the sample, how much parent was in the sample, that their model of gravitational physics is true, and I'm sure there are some inside the formula such as constant variables.. This is getting a bit off-topic for this thread, but there are two basic methodologies for dating rocks. The first (and oldest known) is relative dating of layers by the law of superposition (wiki):
quote: This is still useful today, because not all types of rock are datable by radiometric methods: dating a layer above the target rock and one below then provides a window of age for the target rock. The second methodology is of course radiometric methods, and for this I refer you to an excellent reference:
quote: This provides an excellent overview of all types of radiometric dating methods. Enjoyby 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)
|
|||||||||||||||||||||||||||||||||||||||||||||||
JonF Member (Idle past 194 days) Posts: 6174 Joined:
|
The assumptions are the the system is closed, the original isotopic composition can be estimated, the decay rates have been very nearly constant I prefer "premises" to "assumptions" since the latter connotes lack of solid foundation. The system is rarely assumed closed. Isochron methods indicate if the system has been open and fails to produce a date. Ar-Ar and U-Pb (the two by far the most widely used) also indicate if the system has been opened and often produce a valid date anyway. Isochron methods produce the original isotopic composition and a date as part of the method. In Ar-Ar the original isotopic composition seldom affects the date. In U-Pb (almost always on zircons) the crystallization process readily incorporates Uranium and strongly rejects lead so the original ratio of lead to Uranium is always zero or infinitesimal. The absolute constancy of the decay rates of relevant isotopes under terrestrial conditions is as well established as the atomic constituents of a water molecule. The processes that govern decay are fundamental to the operation of the Universe, and changes would leave unmistakable traces in an astonishing number of places. We've looked; they aren't there. http://www.talkorigins.org/origins/postmonth/oct01.html, The Talk.Origins Archive Post of the Month: August 2006.
|
|||||||||||||||||||||||||||||||||||||||||||||||
Taq Member Posts: 10073 Joined: Member Rating: 5.2
|
DOCJ writes: I'm looking at the information and a few of the assumptions I'm seeing are how much daughter product was in the sample, how much parent was in the sample, that their model of gravitational physics is true, and I'm sure there are some inside the formula such as constant variables.. None of them are assumptions in the truest sense. They are more akin to the assumptions you use with any instrument and measuring technique. Let's use electronic scales as an example. When you are using electronic scales you assume that gravity is the same, the natural laws governing electricity (i.e. Ohm's Law) are the same, and you are also assuming that magical leprechauns are not producing false data. Radiometric dating is the same.
Constant decay rates: In order for decay rates to change you would need to change the fundamental forces of nature, specifically the strong and weak nuclear forces. Since we observe that these forces are the same throughout the universe, as demonstrated by astronomical observations, we can be very confident that these were the same in the past. There are also specific observations of past decay rates such as the decay of isotopes in Supernova 1987a 170,000 light years away (hence 170,000 years ago) where they were able to measure the decay rates of at least one isotope.
Presence of daughter isotope in newly formed rock: You can entirely avoid this problem by using isochron dating which can actually measure the concentration of daughter product in the newly formed rock. For non-isochron methods, this assumption has already been checked in rocks that are from known and historic volcanic eruptions. For example: "Two extensive studies done more than 25 years ago involved analyzing the isotopic composition of argon in such flows to determine if the source of the argon was atmospheric, as must be assumed in K-Ar dating (Dalrymple 1969, 26 flows; Krummenacher 1970, 19 flows). Both studies detected, in a few of the flows, deviations from atmospheric isotopic composition, most often in the form of excess 40Ar. The majority of flows, however, had no detectable excess 40Ar and thus gave correct ages as expected. Of the handful of flows that did contain excess 40Ar, only a few did so in significant amounts. The 122 BCE flow from Mt Etna, for example, gave an erroneous age of 0.25 0.08 Ma. Note, however, that even an error of 0.25 Ma would be insignificant in a 20 Ma flow with equivalent potassium content. Austin (1996) has documented excess 40Ar in the 1986 dacite flow from Mount St Helens, but the amounts are insufficient to produce significant errors in all but the youngest rocks."Radiometric Dating Does Work! | National Center for Science Education At worst, there is enough atmospheric 40Ar in newly formed igneous rock to cause a difference of just 0.25 million years. The real strength of radiometric dating is that there are several independent isotope systems that can be used to cross check each other. For example, you can use K/Ar, U/Pb, and Rb/Sr. If radiometric dating didn't work then there would be no reason to predict that these three completely independent isotope systems would produce the same dates, yet they do: "There are several important things to note about these results. First, the Cretaceous and Tertiary periods were defined by geologists in the early 1800s. The boundary between these periods (the K-T boundary) is marked by an abrupt change in fossils found in sedimentary rocks worldwide. Its exact location in the stratigraphic column at any locality has nothing to do with radiometric dating it is located by careful study of the fossils and the rocks that contain them, and nothing more. Second, the radiometric age measurements, 187 of them, were made on 3 different minerals and on glass by 3 distinctly different dating methods (K-Ar and 40Ar/39Ar are technical variations that use the same parent-daughter decay scheme), each involving different elements with different half-lives. Furthermore, the dating was done in 6 different laboratories and the materials were collected from 5 different locations in the Western Hemisphere. And yet the results are the same within analytical error. If radiometric dating didn’t work then such beautifully consistent results would not be possible."Radiometric Dating Does Work! | National Center for Science Education Here is the table that the quote is describing:
Edited by Taq, : No reason given.
|
|||||||||||||||||||||||||||||||||||||||||||||||
JonF Member (Idle past 194 days) Posts: 6174 Joined: |
Wow, what a load of horses**t! The KBS Tuff story is much more complex than that. Some dates were discarded, all for explicit and objective explanations of why they were incorrect. That's the real standard practice; nobody discards data without stating an objective reason. IIRC the initial range of dates was significantly smaller.
I wrote more at Message 5 Edited by JonF, : No reason given.
|
|||||||||||||||||||||||||||||||||||||||||||||||
Taq Member Posts: 10073 Joined: Member Rating: 5.2 |
JonF writes: IIRC the initial range of dates was significantly smaller. The initial spread in the data was that large. It appears that the first samples contained a mixture of really old material that had eroded and mixed with the new material (lahars?). However, once this problem was identified they started getting a much smaller spread in dates. "In a study to test the feasibility of dating samples from the tuff, the samples were contaminated with non-juvenile components which could not be separated out, giving ages over 200 million years. It was recommended that new samples be collected from which suitable individual crystals could be separated (Fitch and Miller 1970). These new samples were dated at 2.61 +/- 0.26 million years, based on the 40Ar/39Ar dating method (Fitch and Miller 1970). "CD031: KBS Tuff dating Edited by Taq, : No reason given.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1732 days) Posts: 4696 From: Colorado, USA Joined:
|
I prefer "premises" to "assumptions" since the latter connotes lack of solid foundation.
Complete agreement. I never know how far to simplify things and use common terminology. Although, I have to say that radiometric dating has changed a lot since I had any of that kind of work done. The system is rarely assumed closed. Isochron methods indicate if the system has been open and fails to produce a date. Ar-Ar and U-Pb (the two by far the most widely used) also indicate if the system has been opened and often produce a valid date anyway. Isochron methods produce the original isotopic composition and a date as part of the method. In Ar-Ar the original isotopic composition seldom affects the date. In U-Pb (almost always on zircons) the crystallization process readily incorporates Uranium and strongly rejects lead so the original ratio of lead to Uranium is always zero or infinitesimal. One thing that most people do not understand is that if there a problem with a date it's kind of obvious from the viewpoint of an experienced researcher. In fact, right now I'm dealing with data that just looks bad for various reasons. It's going to take some more work. Same thing with the KBS Tuff. It didn't quite fit the known geology. And there is always an explanation.
|
|||||||||||||||||||||||||||||||||||||||||||||||
DOCJ Inactive Member |
I'm merely interested in the truth about dating methods. The age debate wouldn't refute my faith because it is adaptable. I generally view conventional science as a out dated way of thinking. I don't think all of the views are accurate in describing the universe. I'm just interested in the truth. In interpreting your response, it does seem as if you do not care about the accuracy of dating. It's as if you are fine with whatever. Which is fine but I'm more interested with the truth. And if you represent the main way of thinking I can definitely see why there is a debate. Christians who are in seek mode are looking to conclude in truth not on bias with regards to dating. If your attitude is a standard within the geology field, it's not a good thing. Every detail should matter, anchoring is unhealthy. FYI: I believe in the electrical model of the universe, birkeland currents, plasma physics, and accept gravitational physics as a weak force. Essentially the birkeland current would develop a universe that changes the composition of material, and the like due to the electrical current that would connect everything in the universe. There is absolutely no way to determine with out a doubt the age of the universe or the earth with conventional methods.
Electricverse Electric Sun NoBB Edited by DOCJ, : Clarification Edited by DOCJ, : Clarification
|
|
|
Do Nothing Button
Copyright 2001-2023 by EvC Forum, All Rights Reserved
Version 4.2
Innovative software from Qwixotic © 2024