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Author Topic: Carbon Dating?
Sid Meier
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Yo, I'm having debates with ever-so-slightly christian people at my college and they say that carbon dating is unreliable can aynone tell me what the process is? I tried looking for it in my Isaac Asimov science articles but no-go so can anyone here explain it for me? Thank you.
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Corwin
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Let me introduce you to "howstuffworks":

Carbon dating.

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King of Men
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Carbon dating works as follows : There are two isotopes of carbon in the atmosphere, C-12 (which is stable) and C-14 (which decays with a half-life of about 5000 years). C-14 is constantly being produced in the atmosphere by some process I don't offhand remember, maybe the solar bombardment. At any rate, the ratio of C-14 to C-12 is reasonably constant (though see below) and your body, for obvious reasons, has the same ratio in its cells. When you die, however, you are no longer replenishing the C-14 in your cells, and the percentage of C-14 starts to decrease in an extremely predictable way. By measuring the percentage, and knowing what percentage your body started with, it is easy to figure out when you died.

Now, one criticism of this is that we don't strictly speaking know that the C-14 ratio has been constant over the past 50000 years. This is a valid criticism as far as it goes. However, we get around it by dating objects in other ways, and then seeing what we get with the carbon method. This allows us to estimate the C-14 content in the atmosphere throughout history, and so use the carbon method on objects where other methods are not available. If this seems complex, well, science is a lot like that. The reason we trust carbon dating is that it gives consistent results. Like most other theories and methods, it doesn't need to stand on its own feet : It interlocks (without contradiction) with dozens of other facts, methods, and hypotheses, forming a strong edifice.

A word of caution : Carbon dating is not magic. It only works out to 50000 years or thereabouts. After that, the C-14 ratio is so small that it is difficult to measure. It needs considerable care, so you don't contaminate your sample with modern materials. And it only works on things that were once alive; however, this covers a surprising range of human artifacts, including most clothes.

Edit : Arrgh! Linking is cheating!

Edit2 : Spelling. Clearly I should eat breakfast before explaining complicated stuff.

[ January 14, 2005, 11:21 AM: Message edited by: King of Men ]

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Corwin
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Boy, you sure type fast! [Razz]

And no, linking isn't cheating, it's reusing stuff, a pefectly acceptable tactic. [Smile]

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vwiggin
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Maybe this article can give you some insight into their position:

What about carbon dating? (Answers in Genesis)

quote:
Are we suggesting that evolutionists are conspiring to massage the data to get what they want? No, not generally. It is simply that all observations must fit the prevailing paradigm. The paradigm, or belief system, of molecules-to-man evolution over eons of time, is so strongly entrenched it is not questioned—it is a ‘fact.’ So every observation must fit this paradigm. Unconsciously, the researchers, who are supposedly ‘objective scientists’ in the eyes of the public, select the observations to fit the basic belief system.

We must remember that the past is not open to the normal processes of experimental science, that is, repeatable experiments in the present. A scientist cannot do experiments on events that happened in the past. Scientists do not measure the age of rocks, they measure isotope concentrations, and these can be measured extremely accurately. However, the ‘age’ is calculated using assumptions about the past that cannot be proven.

We should remember God’s admonition to Job, ‘Where were you when I laid the foundations of the earth?’ (Job 38:4).

Those involved with unrecorded history gather information in the present and construct stories about the past. The level of proof demanded for such stories seems to be much less than for studies in the empirical sciences, such as physics, chemistry, molecular biology, physiology, etc.


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vwiggin
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quote:
And no, linking isn't cheating, it's reusing stuff, a pefectly acceptable tactic.
Efficiency is a highly evolved form of laziness. [Smile]
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Corwin
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Ambition is a poor excuse for not having enough sense to be lazy. [Razz]
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King of Men
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Bah. My explanation was better anyway, since it addressed the issue of non-constant C-14 concentration. [Razz]
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vwiggin
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Luckily, my highest ambition is to be as lazy as possible. [Big Grin]

[ January 14, 2005, 11:24 AM: Message edited by: vwiggin ]

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Dagonee
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OK, quick question: is the rate of C-14 production something that can be changed by conditions on earth? I've always wondered what the basis is for the assumption that the ratios haven't changed.

It seems the ratio would be based on the amount of cosmic rays hitting the earth, but if something happened that deflected, absorbed, or somehow prevented the rays from getting through in the same percentage, couldn't the ratio change over time?

it seems we could test this indirectly by carbon dating some corpses with known dates of death. Has this been done in large enough numbers to confirm the past ratios?

Dagonee
Edit: Never mind, KoM posted while I was distracted.

[ January 14, 2005, 11:30 AM: Message edited by: Dagonee ]

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PSI Teleport
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Oh, interesting question. Would the amount of dust in the air (from a meteor strike) affect the amount of C-14 in the creatures that survived it? (Thinking specifically about the meteor strike that may have killed the dinosaurs, here.)

Edit: [Razz] Nevermind. *resists urge to delete*

[ January 14, 2005, 11:32 AM: Message edited by: PSI Teleport ]

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skillery
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When we apply our perception of time to events that happened in the past, we assume that time "flows" at a constant rate. That is, we assume that events occur at a constant rate, down to the subatomic level.

There was an excellent issue of Scientific American last year that focused on time and the measuring of time. One article summarized that there is no such thing as time and that time doesn't "flow" at all. What we call time is a manifestation of the laws of thermodynamics and man's perception of a sequence of events.

Whether a sequence of events happens quickly or slowly is a matter of perception. And because our brains and all our measuring devices are part of the physical world we could never know whether something is happening fast or slow because we don't have some absolute standard that resides outside the physical world.

You observe an egg falling from a table. In the background, a clock with a second hand is ticking. You perceive the passage of time because the egg is moving and the second hand on the clock is moving. How fast did the egg fall? You would rely on the clock to tell you. How fast was the second hand moving? You rely on some atomic clock at the National Bureau of Standards to tell you. How fast was that atom pulsating? As fast as it wants. Because all the measuring devices, including our brains are made up of physical matter, the whole system could speed up or slow down, and we'd never perceive the difference.

So God shows Moses a vision of the creation of the earth. How fast was that video tape rolling? Who's time frame was used?

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PSI Teleport
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Yes, that's interesting. Time does seem to be an arbitrary measurement of how long it takes for things to move.
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Glenn Arnold
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Speaking of time, I read somewhere that there is a theoretical "minimum" period of time.

Like a subatomic time particle (for analogy) that equates to some really small fraction of a second, and that an experiment had been done that was consistent with that minimum value.

Did anyone else hear about that?

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Glenn Arnold
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quote:
So God shows Moses a vision of the creation of the earth. How fast was that video tape rolling? Who's time frame was used?
I know that Moses is credited with writing the Torah, but I had never heard where this idea came from. Is there a passage in the Bible that describes this vision?
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dkw
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No.
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Dagonee
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quote:
Speaking of time, I read somewhere that there is a theoretical "minimum" period of time.

Like a subatomic time particle (for analogy) that equates to some really small fraction of a second, and that an experiment had been done that was consistent with that minimum value.

Did anyone else hear about that?

Yes, there are minimum time and distance units called "Planck Time" and "Planck Length." Edit: They're not quite as you described, though. This is probably what you heard about.

The Planck Time is 5.39121 × 10-44 seconds, the Planck length is 1.61624 × 10-35 meters.

[ January 14, 2005, 12:43 PM: Message edited by: Dagonee ]

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PSI Teleport
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I don't know how it would be possible to determine that that measure of time remained consistant.

[ January 14, 2005, 12:43 PM: Message edited by: PSI Teleport ]

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Corwin
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quote:
Did anyone else hear about that?
Nope, I haven't. And it's strange, because it would be a pretty "big" thing in the physics world... I'll check this out probably during the weekend.

Edit: Thanks Dag for the link. As you indicated, those are NOT what he actually said in his post though...

[ January 14, 2005, 12:46 PM: Message edited by: Corwin ]

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Dagonee
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I did read in in a Pembrose book that nothing meaningful can be said to happen in under that time, but I'm not sure what he meant by that.
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SausageMan
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Unfortunately, as much as I have studied dating techniques, I have yet to completely understand them.

But the impression I got was that even in the secular, scientific world, carbon dating is only reliable up to about 10,000 years (Creationists claim that it's 6,000 years, or not reliable at all). I know for a fact that it's not nearly as long as most people think, and it's a common misconception that carbon dating has been used to date the world.

Now I do know that there's another form of dating, Potassium-Argon dating, that is useful from something like 100,000 years ago to a much longer time back than that. I'm sorry my numbers aren't entirely accurate, but like I said, as much as I have looked into this subject, I have never fully understood it.

Curiously enough, I believe that the "gap" between when carbon dating stops and potassium-argon starts is pretty much the exact time period when man made their most crucial evolutionary developments. So there's a lot missing there in evolutionary theory.

But I know little of this subject. If anyone can make some sense of this article, it might help.

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fugu13
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Every single example of creationists asserting a flaw in carbon dating that I have seen is on a sample that scientists would classify, due to the natural limitations of carbon dating, as not dateable by carbon dating.

This lack of honesty (or intelligence, take your pick) by creationists who use such "evidences" is annoying.

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skillery
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Glenn Arnold:

quote:
Is there a passage in the Bible that describes this vision?
Does it matter which Bible:

quote:
1 AND it came to pass that the Lord spake unto Moses, saying: Behold, I reveal unto you concerning this heaven, and this earth; write the words which I speak. I am the Beginning and the End, the Almighty God; by mine Only Begotten I created these things; yea, in the beginning I created the heaven, and the earth upon which thou standest.

2 And the earth was without form, and void; and I caused darkness to come up upon the face of the deep; and my Spirit moved upon the face of the water; for I am God.

3 And I, God, said: Let there be light; and there was light.

4 And I, God, saw the light; and that light was good. And I, God, divided the light from the darkness.

5 And I, God, called the light Day; and the darkness, I called Night; and this I did by the word of my power, and it was done as I spake; and the evening and the morning were the first day.

Creationists like to think that "day" means 1000 years. I don't know where they come up with that number. It seems fruitless to try to determine the age of the earth from the Biblical account. We have no idea how much absolute time elapsed in Moses' "day."
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Sid Meier
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Also if you are an omnipotent being what is your concept of time? After all the Earth standard "day" is different from the Martian standard "day". (I forget by how much) And thanks for the info guys I'm trying to arm myself with as much facts as possible when I debate these people.
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skillery
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quote:
if you are an omnipotent being what is your concept of time
If you are an omnipotent being, time means nothing. You've got the power at your disposal to undo anything that happens, as required by the second law of thermodynamics. You can put the egg back together, raise it back to the table top, turn back the second hand on the clock, and undo the memories of all who observed the egg falling. The event never happened. There is no "before;" there is no "after."
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Lyrhawn
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There are still other Isotopes besides Carbon-14 that are used for dating, especially beyond the 50,000 year mark. The different isotopes are used for different time periods because they are better at measuring that specific time period. I don't remember offhand what they are, but I think U-233 was one of them, or something like that. I haven't had to do anything with carbon dating since AP Biology three years ago. I don't know if the other forms are as reliable, but they are used.
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HollowEarth
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yeah KoM its the solar bombardment, as far as I know too. You also left out C-13, the other stable isotope.
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Alucard...
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I thought this was going to be a thread on singles dating, but couldn't figure out how carbon factored into all of it...
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The Rabbit
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I highly recommend carbon dating or at least dating carbon based life forms. Some years ago I dated a carbon based life form who I eventually married and have never regretted it. Quite frankly, none of the relationships I've had with silicon, iron, aluminum or protactinium have been anywhere near as rewarding. Definitely date carbon.
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Dagonee
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I thought it was about the appropriate time to give someone a diamond.
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The Rabbit
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Comparisons of radio carbon dates with bristlecone pine tree ring data indicate that radiocarbon dating is accurate to about 10% for the past 6-7 thousand years. Radiocarbon dating is, however, not the only way that fossils are dated. In fact, it is rarely used for fossils since it is only valid back to around 50,000 BP.
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Dagonee
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That brings up an interesting question - the links say all living things have the same percentage C-12/C-14 they say. But does a really old tree replace all its carbon throughout its whole structure the whole time it's alive?
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King of Men
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Hmm, good point. If there's dead tissue in the middle, no, it proabably doesn't.
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Insanity Plea
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However, if it is dead tissue, it's most likely rotten, and therefore there's bacteria and fungus that is growing, which would give as accurate carbon date.

The uranium used for dating is (238)U which turns to a rare isotope of lead (206)Pb, (your normal lead is 207), the half life for uranium is roughly 4.5x10^9 years (4.5 billion years).
The half life of Potasium to Argon is 1.2x10^9, and rubidium to strontium is 50x10^9.

This wikipedia page finally loaded for me, seemingly quite comprehensive.
Satyagraha

[ January 15, 2005, 01:01 AM: Message edited by: Insanity Plea ]

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Lyrhawn
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U 238! I was pretty close (I said U 233). Considering I was just working from memory, I'd say that's pretty solid.
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