How C14 works
- Status - under construction
- Index
- Master index of this blog
- Introduction to this blog
- Revision history
- Introduction
- Piggy-bank example
- Given/assumed
- Figuring the percent
- And there you have it
- Revsion history
- Date - activity
- 11/08/06 - introduction, piggy bank
- 11/07/06 - started page
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- Introduction
Because this will be a long presentation (a couple of pages) it seemed correct to isolate it. The process that 14C goes through happens over thousands of years. Trying to explain in detail a process that occurs on that time scale would be difficult for me so I will use a piggy-bank example to introduce the concept.
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- The piggy bank example
Suppose you own an empty piggy-bank. In this case, you want to save some money but you want to spend some too. So, you decide to put a dime a day into the initially empty bank and take out 10% of what is in there for spending money. Here is how the first several days would go:
- 10 cents in makes 10 cents in the bank; 10% of 10 cents in the bank is 1 cent for spending money leaving 9 cents
- 10 cents in makes 19 cents in the bank 10% of which is (rounded up) 2 cents to spend leaving 17 cents
- 10 cents in = 27 cents in the bank, 10% of that is 3 cents to spend leaving 24 cents
- add 10 = 34, 10% = 3, 31 left in the bank
- add 10 = 41, 10% = 4, 37 left in the bank
- add 10 = 47, 10% = 5, 42 left in the bank
- add 10 = 52, 10% = 5, 47 left in the bank
- add 10 = 57, 10% = 6, 51 left in the bank
- add 10 = 61, 10% = 6, 55 left in the bank
- add 10 = 65, 10% = 7, 58 left in the bank
- add 10 = 68, 10% = 7, 61 left in the bank
- add 10 = 71, 10% = 7, 64 left in the bank
- add 10 = 74, 10% = 7, 67 left in the bank
- add 10 = 77, 10% = 8, 69 left in the bank
As you can see, the pennies available at the end of each turn increases rapidly at first then begins to grow more and more slowly as the 10% coming out takes a larger amount. After several more turns, there would obviously be over 90 cents in the bank. When the amount in the bank became 95 cents then you would put a dime in and take a dime out (9.5 cents rounded up). The amount in the bank would remain 95 cents forever.
This is the process for 14C also.
One final note: visualizing taking 10% out was easy to understand but the calculation would work the same if we said we wanted to keep 90% in the bank.
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- Given/assumed
Now, we have an idea of the process. What do we know?
- the atmosphere and anything that breathes or absorbs air becomes the bank where the 14C is stored
- 22 formations occur per second (looking for verification) becomes the deposits
- any one 14C atom will probably stay in the atmosphere for 5715 years (half-life of 5715 years)
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- Figuring the percentage
The percent to be taken out (the spending money in the piggy-bank example) can be calculated. What percent of removal will result in one-half (50%) as much being in the atmosphere after 5715 years? Another way to say this is what percent would I need to keep each turn to have 50% remaining in 5715 years. The value of 0.99988 works. On a calculator which can process exponentiation (y^x) enter "0.99988 y^x 5715 =" and the result is about .503 or roughly 50% remaining after 5715 years.
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- And there you have it
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Carbon 14
- Status - under construction
- Index
- Master index of this blog
- Introduction to this blog
- Revision history
- Introduction
- What material can be dated
- Why not other material
- What plants and animals can be dated
- Why not other plants and animals
- What ages can be dated
- Why not other ages
- What happens outside those parameters
- How is the measuring done
- Revsion history
- Date - activity
- 11/03/06 - started layout
- 11/01/06 - started page
- Introduction
Radiocarbon dating (or radiometric dating) is a interesting subject, even for a novice. While there are many factors to take into account, the factors are understandable at a high level. Radiometric dating is used, as the name implies, to discover the age of a substance which contains carbon atoms. The age is expressed as, for example, 10,000 years BP (before the present).
The first set of issues are what material, what subset of the material, and what ages of the material can be dated by this method and what happens when material outside those parameters is dated.
The second set of issues is the handling, preparation, and measuring of the substance.
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- What material can be dated
Clearly, since the method is called carbon-14 dating (14C) this process is exclusivly related to matter containing carbon. Carbon-14 is created when a nitrogen atom (1xN) accepts a xxx. The modified carbon atom is unstable (it doesn't want the extra xxx) and will eventually give the xxx up.
The material must be from a plant or animal (a living thing) because the material must be part of something that breathed or absorbed 14C from the atmosphere or ate another living thing that did.
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- Why not other material
Obviously, material without any carbon in it can not have the carbon measured.
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- What plants and animals can be dated
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- Why not other plants and animals
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- What ages can be dated
An atom of 14C has a half life of approximately 5715 years. This means that if a sample once contained two atoms then 5715 years later the sample probably contains one. If a sample once contained four atoms of 14C then 11,430 years later it probably contains one.
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- Why not other ages
A sample of once living material containing carbon will have 14C from three sources. The first is the 14C from the atmosphere. The second is the 14C created while the sample was buried. The third is contamination which will be discussed a little later. In this section we assume that the sample is not contaminated.
After many (just over 45) half-lives have passed then there is so little 14C remaining that the "real" 14C can not be separated from the "background" 14C.
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- What happens outside those parmeters
If one is trying to discredit radiometric dating then it is tempting to prove that the method is broken by using it outside the parameters. This is similar to complaining that a body thermometer does not work because it will not correctly give the temperature of boiling water.
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- How is the measuring done
The measuring is accomplished using a mass-spectrometer. This instrument measures the ratio of 14C to 12C. Note that counting the number of decays is not the method used and this is due to the long period of time between decays.
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NosyNed says in message 3 that "Radio carbon dating is good for, at the extremes, up to about 50,000 years."
Bret reports in message 9 that "Saying C14 is produced within the earth is based on faith (belief) not facts by fringe scientists that have the need to believe C14 is being produced within the earth under normal conditions."
nemesis juggernaut gives a highly rebutted introduction to carbon dating in message 17 (especially in message 21 by crashfrog).
JonF reports in message 18 that
in message x that
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The things people say
- Status - under construction
- Index
- Master index of this blog
- Introduction to this blog
- Revision history
- a pack of creationists
- A pack of creationists
Mr. Neil asks in the comments at the end of the article:
"Here's a facetious question: Why do you suppose it's fairly easy for an evolutionist to hide in a pack of creationists, but it's nearly impossible for a creationist to hide in a pack evolutionists?"
I respond with the question "Why do you suppose it's fairly easy for a terrorist to hide in a pack of peaceful citizens, but it's nearly impossible for a peaceful citizen to hide in a pack of terrorists?"
Is the question revelant to the discussion? What does the answer prove?
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