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Author Topic:   Adjusting decay constants?
Sylas
Member (Idle past 5287 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 1 of 4 (87920)
02-21-2004 6:48 PM


In Message 17, jazzlover_PR has commented further on claims that decay constants are adjusted.
jazzlover_PR writes:
I will admit that i didnt express the variables correctly but it is also the first time that i see a negative lambda sign in there. In every textbook ive check out its a negative k. But the real problem is that youre accusing me of not knowing of what i talking about when apparently youre the one that has nly taken a basic calculus course.
Just like with the population growth model the decay model has to have its constant adjusted every certain time. Graphically if the constant is left unchanged the curve will not reach the values you want so you adjust them by taking different points on the graph to change your initial population which will eventually produce a change in the constant. you make this change again when the values obtained are starting to look illogical. More on this when i have more time
Decay constants are constant. There is no adjustment applied of any kind. I have not seen this claim before in over ten years of discussing these subjects. I suspect you are using a source which is incorrect anyway, and then adding a layer of misunderstanding of your own. If you could give a reference, it would help.
The most likely source of confusion here is something related to radiocarbon dating.
There are adjustments routinely applied with C-14 dating, but it has nothing to do with decay constants. All dates are corrected according to a standard calibration curve. In the notation you have used, it is an adjustment based on variations in Ti, the initial amount of the radioactive isotope; since the background C-14 level varies over time.
However, this adjustment is standard. It is an essential step in the method. It can't be left out, and it can't be an adjustment to fit predetermined goals, because the calibration curve is a standard. Adjusting values to fit desired goals is scientific suicide. It can kill a career overnight.
Another source of confusion may be based on claims the decay rates can vary. In fact, the decay rates used in geological dating are completely constant; any variation is far below the most accurate levels of detection we have available.
But there are two kinds of variation which have been known for decades, and which have recently appeared in a rather misleading form in some creationist writings.
There is one exception only to the principle that decay rates used in geology are constant, and that is Be-7; but it is not used in dating. Beryllium 7 has a half life of only about 55 days, and it is used sometimes to measure short term processes like sediment flows. The decay rate of Be-7 shows very slight variations dependent on its chemical environment. Generally this means that you should use slightly larger error bars on results to account for variations, in cases where this could have an effect. This it is not a way to adjust results in a predetermined direction.
Another case which is often cited is Rhenium-187. Re-187 has a half life of about 45 billion years, and is used as an isochron method for long range geological dating. Re-187 has a second decay mode which kicks in when the atom is completely ionized, and this second mode has a half life of 33 years. This has some relevance for old calculations attempting to infer the age of the universe from isotope distributions, since under extreme conditions in the early universe the second decay mode becomes significant. But in geology it is irrelevant; because a fully ionized Rhenium atom requires conditions that would instantly reduce any rock to plasma; about 200 million degrees if I recall correctly.
I also confess to a macabre curiosity concerning how you conclude I have only taken a basic calculus course.
Cheers -- Sylas

Replies to this message:
 Message 2 by JonF, posted 02-21-2004 7:00 PM Sylas has not replied
 Message 3 by Harlequin, posted 02-22-2004 11:25 AM Sylas has not replied

  
JonF
Member (Idle past 195 days)
Posts: 6174
Joined: 06-23-2003


Message 2 of 4 (87922)
02-21-2004 7:00 PM
Reply to: Message 1 by Sylas
02-21-2004 6:48 PM


also confess to a macabre curiosity concerning how you conclude I have only taken a basic calculus course.
ROFLMAO! Me too!

This message is a reply to:
 Message 1 by Sylas, posted 02-21-2004 6:48 PM Sylas has not replied

  
Harlequin
Inactive Member


Message 3 of 4 (87964)
02-22-2004 11:25 AM
Reply to: Message 1 by Sylas
02-21-2004 6:48 PM


quote:
jazzlover_PR writes:
I will admit that i didnt express the variables correctly but it is also the first time that i see a negative lambda sign in there. In every textbook ive check out its a negative k. But the real problem is that youre accusing me of not knowing of what i talking about when apparently youre the one that has nly taken a basic calculus course.
Traditionally lambda is used in radioactive decay though k is sometimes used especially in places where it is easier to type a 'k' then a 'λ' or in math textbooks which are not going to give every symbol that every field might use to represent a constant of decay or growth. Math textbooks have things to do besides teaching the conventions of specialized fields. Maybe instead of looking at at math textbook, Jazzlover should look at book on radiometric dating. Dalrymple's The Age of the Earth uses lambda for example.
But Jazzlover, before you accuse Sylas of lack of a knowledge of calculus, maybe it is time for you to consider your understanding of pre-algebra. For Pete's sake, it does not matter what letter or symbol one uses for the decay constant so long as as you are clear what it represents and are consistent in how you use it.

I do my best to dump jellybeans on the creationists' parade.

This message is a reply to:
 Message 1 by Sylas, posted 02-21-2004 6:48 PM Sylas has not replied

  
Loudmouth
Inactive Member


Message 4 of 4 (88163)
02-23-2004 2:23 PM


I find the whole accusation that decay rates are changed to be ludicrous. Every published paper uses the same decay constant, or SLIGHTLY adjusted rates to reflect the most recent atomic decay research. It isn't geologists that are creating these decay rates, it is physicists working with atomic theory.
Secondly, if any YEC thinks that some hanky-panky is going on with the measurements, what is stopping AiG or ICR from going to the same rock formations and testing the rock themselves? If they come up with the same ratios of parent to daughter products, all they are left with is "either the decay rates were different in the past, or our current measurements are 6,000% off." Doesn't make much sense either way, given our experience with nuclear weapons and nuclear power plants.
So my challenge to the YEC's who disagree with decay rates, show me any data (not rhetoric) that shows how decay rates can drastically change in an Earth like environment. If you don't have any data, than why shouldn't the data we do have, such as supernovae and the Oklo reactor, stand on its own as evidence of constant decay rates?

  
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