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Author | Topic: Does radio-carbon dating disprove evolution? | |||||||||||||||||||||||||||||||
RAZD Member (Idle past 1431 days) Posts: 20714 From: the other end of the sidewalk Joined: |
I see most of the points have been covered already but lets sum it up and see where it goes okay?
(1) 14C dating is used to date objects containing 14C absorbed by organisms from the atmosphere during their lifetime - after death the 14C decays thus giving an indication based on the half life of 14C of when the organism lived. What is measured is the ratio of 14C to 12-C (the stable carbon isotope). Assumptions used:
As a result:
-- this includes marine life that use alternative sources of carbon, usually carbonates, and any life forms that obtain substantial portions of their diet from such marine life. (2) The source of atmospheric 14C is 14-N plus bombardment by a neutron, a relatively rare occurrence that results in one 14C atom for every 10^12 12-C atoms.(= 1/1,000,000,000,000 carbon atoms) The method
There are three principal isotopes of carbon which occur naturally - C12, C13 (both stable) and C14 (unstable or radioactive). These isotopes are present in the following amounts C12 - 98.89%, C13 - 1.11% and C14 - 0.00000000010%. Thus, one carbon 14 atom exists in nature for every 1,000,000,000,000 C12 atoms in living material. In other words the amount of 14C in your body could be concentrated into a small grain of pure carbon that would be very hard to see in your hand with the unaided eye
200 lbs x 16oz/lb
... if you were pure carbon ... and we are 98% water ...------------------------ = 0.0000000032 ounces ... 1,000,000,000,000} As a result:
(3) The half-life of 14C is 5715 years and the practical limit for 14C dating is45,000 to 50,000 years (depending on sources, but a good one was already provided: Radiometric Dating, A Christian Perspective, by Dr. Roger C. Wiens (click) - a lot of other useful information too, so you'll have to either (a) read the whole thing or (b) search the site for "carbon-14" references. Let's say the limit is 40,000 years As a result:
Now normally 0.8% is not considered a small number, but remember that we are already dealing with a small initial sample, but the other reasons that this is the practical limit of 14C dating are:
As a result:
(4) 14C content of extremely ancient samples correlates with radioactivity rather than age (and I would have used the same example Percy already used in Message 65 of the 14C content in oil by Kathleen Hunt), from Percy's link:
So, the physicists want to find fossil fuels that have very little 14C. In the course of this work, they've discovered that fossil fuels vary widely in 14C content. Some have no detectable 14C; some have quite a lot of 14C. Apparently it correlates best with the content of the natural radioactivity of the rocks surrounding the fossil fuels, particularly the neutron- and alpha-particle-emitting isotopes of the uranium-thorium series. Dr. Gove and his colleagues told me they think the evidence so far demonstrates that 14C in coal and other fossil fuels is derived entirely from new production of 14C by local radioactive decay of the uranium-thorium series. Many studies verify that coals vary widely in uranium-thorium content, and that this can result in inflated content of certain isotopes relevant to radiometric dating (see abstracts below). I now understand why fossil fuels are not routinely used in radiometric dating! (bold color yellow mine for emPHAsis) ... As a result:
(5) PurpleYouko's Message 68 information regarding spontaneous fission producing neutrons in those same kinds of radioactive materials -- those same kinds of neutrons and energy that caused the formation of 14C from 14N in the atmosphere ... As a result:
Logical conclusions:(1) The world is at least 40,000 years old (whether ancient carbon sources have elevated levels of 14C due to radioactivity or not) and (2) 14C dating is reliable when used for the proper kinds of samples and the age limitations of the method, and when it is controlled for known sources of errors -- non-organic samples, non-atmospheric organic samples, and radioactivity contaminated samples - ie when it is used honestly. Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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johnfolton  Suspended Member (Idle past 5618 days) Posts: 2024 Joined: |
Alpha particles ejected by radioactive decay are indeed relatively slow, traveling at only about 15,000,000 m/s (34,000,000 miles per hour). The alpha particle has very little energy and is only able to move a few centimeters in the air. The problem is within the earth the alpha particle is absorbed by the sediments. Its this self shielding property of the earth (absorbing the alpha particle)all the alpha particle needs is a couple of electrons and it can not violate the coloumb barrier. If the alpha particle has not enough energy to penetrate a layer of skin it does not have the energy to cause fission unless it comes in contact with beryllium. Even then any neutrons generated would have to target N14 and within the earth soil dynamic enrichment is said to be N15. In soil dynamics (assimilation, nitrification, and denitrification) it always result in N-15 inrichment it did not say N14. I find this interesting because you need N-14 within the earth not N-15. Do you know if your fungus, bacteria are assimulating N15, it appear if so then its a non factor in respect to C14 generation? N14 is a gas so if its not incorporated within the soil why would it not simply returns to the atmosphere? If all N14 is returning to the atmosphere where is your target. Nitrogen - Wikipedia Biologically-mediated reactions (e.g., assimilation, nitrification, and denitrification) strongly control nitrogen dynamics in the soil. These reactions almost always result in N-15 enrichment of the substrate and depletion of the product. http://www.epa.gov/radiation/understand/alpha.htm The health effects of alpha particles depend heavily upon how exposure takes place. External exposure (external to the body) is of far less concern than internal exposure, because alpha particles lack the energy to penetrate the outer dead layer of skin. Edited by johnfolton, : No reason given. Edited by johnfolton, : No reason given.
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RickJB Member (Idle past 5017 days) Posts: 917 From: London, UK Joined: |
I reckon you haven't a clue what you are talking about.
Are you a chemist or physicist? I know I'm not, but do you?
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Percy Member Posts: 22492 From: New Hampshire Joined: Member Rating: 4.9 |
Hi JF,
Nothing in your message constitutes rebuttal, and I'm replying only to correct your errors:
johnfolton writes: Alpha particles ejected by radioactive decay are indeed relatively slow, traveling at only about 15,000,000 m/s (34,000,000 miles per hour). The alpha particle has very little energy and is only able to move a few centimeters in the air. The problem is within the earth the alpha particle is absorbed by the sediments. It looks like you may have used the Wikipedia entry on alpha particle as a reference, since there are a number phrases from that article that appear in your message nearly verbatim, and the order of presentation in your message is the same as the order in the article, and you've included information from the article that isn't even relevant to this discussion, like absorption by human skin. Anyway, to correct your errors, and as the Wikipedia article correctly states, emitted alpha particles have a hell of a lot of energy: "between 3 and 7 MeV. This is a substantial amount of energy for a single particle." 5% of the speed of light is only relatively slow compared to other radiative particles, and it is actually incredibly fast for something as massive as an alpha particle. When something that massive and that fast hits something it can do considerable damage.
Its this self shielding property of the earth (absorbing the alpha particle)all the alpha particle needs is a couple of electrons and it can not violate the coloumb barrier. I very much doubt that acquiring a couple of electrons plays any significant role. What matters is what the alpha particle collides with. With its substantial energy it has little trouble overcoming the coulomb barrier of low atomic weight elements like oxygen, beryllium and carbon. For example, with beryllium the process goes like this:
9Be + a => 12C + n The neutrons produced by this process are now free to participate in the 14C production process by striking a 14N atom:
n + 14N => 14C + p Moving on:
If the alpha particle has not enough energy to penetrate a layer of skin it does not have the energy to cause fission unless it comes in contact with beryllium. As described earlier, alpha particles have an enormous amount of energy. The reason they don't usually penetrate skin isn't due to lack of energy but because of their enormous size. An alpha particle is so large (after all, it's not really a single particle but a 4He nucleus consisting of 4 particles: 2 protons and 2 neutrons) that it is highly unlikely for it to travel very far before striking another atom. Animals are protected from alpha particles by their hair and skin which are damaged when struck, but that damage is usually not a health risk because hair and skin are continually replaced. However, ingested radioactive material can cause enormous damage inside the body since the alpha particles now strike metabolic tissue. As this webpage on Neutron Production relates, one very common way to produce neutrons is to mix a source of alpha particles, in this case 241Am (Americium), with Beryllium. In other words, nuclear labs around the world are producing neutrons via the very process you're claiming is impossible. To directly address the issue of production of 14C in coal, radioactive materials that are mixed in with coal deposits give off alpha particles. Any of these alpha particles that happen to strike nearby beryllium, oxygen or carbon atoms will give off neutrons. Any of these neutrons which happen to strike a 14N atom will transform it into 14C. This explains the residual amounts of 14C found in coal. That these amounts are proportional to radioactivity levels within the coal is further supporting evidence.
Even then any neutrons generated would have to target N14 and within the earth soil dynamic enrichment is said to be N15. In soil dynamics (assimilation, nitrification, and denitrification) it always result in N-15 inrichment it did not say N14. I find this interesting because you need N-14 within the earth not N-15. 99.634% of all nitrogen is 14N. As the very Wikipedia article on Nitrogen that you referenced describes, the enrichment process causes 0.73% of N2 to be 14N15N, and the other 99.27% is almost all 14N2.
Nitrogen - Wikipedia Biologically-mediated reactions (e.g., assimilation, nitrification, and denitrification) strongly control nitrogen dynamics in the soil. These reactions almost always result in N-15 enrichment of the substrate and depletion of the product. This is actually a cut-n-paste, not a summary or derivation, from Wikipedia's Nitrogen article. You appear to be quoting it without understanding it. 15N is always less than 1% of all Nitrogen and is not a significant factor. More than 99% of all Nitrogen in nature is always 14N.
http://www.epa.gov/radiation/understand/alpha.htm The health effects of alpha particles depend heavily upon how exposure takes place. External exposure (external to the body) is of far less concern than internal exposure, because alpha particles lack the energy to penetrate the outer dead layer of skin. This is irrelevant to the discussion, but the website you're quoting is incorrect. Alpha particles have enormous energies. The reason they don't penetrate the skin is because as large and massive particles they are very unlikely to penetrate very far before striking another particle, usually the nucleus of an atom. This is true of any particle - no matter how much energy it has, once it strikes another particle its journey is over. The collision will emit other particles which then begin a journey of their own before in turn striking other particles. To summarize:
--Percy
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PurpleYouko Member Posts: 714 From: Columbia Missouri Joined: |
But is the alpha particle / neutron produced by radon mobile, didn't anything on neutrons being produced by radon, however a neutron will degenerate within minutes to a proton, electron and an anti-neutrino.
No the neutron isn't mobile. It travels in a straight line for an inch or so before it loses its energy.The point is that the N14 atom will need to be in extremely close proximity to the the Radon or other heavy isotope nucleous when it fissions. his is a substantial amount of energy for a single particle, but because alpha particles have a high mass, this does not mean they have high speeds --- in fact, their speed is lower than any other common type of radiation ( particles, -rays, neutrons etc). Because of their charge and large mass, alpha particles are easily absorbed by materials and can travel only a few centimeters in air.
You are quite right here. It is also quite irrelevent since spontaneous fission directly produces a free, high energy Neutron. It doesn't need to first make an Alpha.
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JonF Member (Idle past 194 days) Posts: 6174 Joined: |
The alpha particle has very little energy and is only able to move a few centimeters in the air. The problem is within the earth the alpha particle is absorbed by the sediments. And neutrons are generated, which can (and do) travel great distances. Forget the alpha particles, they're red herrings.
Even then any neutrons generated would have to target N14 ... No, some neutrons will hit 14N atoms and many will hit other atoms. The open question is "how many will hit 14N atoms?"
and within the earth soil dynamic enrichment is said to be N15. In soil dynamics (assimilation, nitrification, and denitrification) it always result in N-15 inrichment it did not say N14. I find this interesting because you need N-14 within the earth not N-15. Read the reference you provided. Overall on the Earth and in rocks, 99.634% of the nitrogen is 14N. Organic processes within soil have some isotopic separation effects, but the vast majority of nitrogen in any sample is 14N. "Enrichment" is not "exclusion"; the organic processes result in very slightly more 15N incorporated than the overall average. Consider the fact that very few fossils are found in paleosols (fossil soils); most are found in sedimentary rocks formed by erosion of igneous and metamorphic rocks, and those rocks have no 15N enrichment.
Do you know if your fungus, bacteria are assimulating N15, it appear if so then its a non factor in respect to C14 generation? They may be slighly preferentially absorbing 15N, but still 90-95% of the nitrogen they contain is 14N.
N14 is a gas so if its not incorporated within the soil why would it not simply returns to the atmosphere? You are very confused. 14N is an atom, which is incorporated in many compounds which are solid at standard temperature and pressure, are included in rocks and soils and what-not (sometimes in just trace amounts), and many of which are required for life and are included in all living and formerly-living things. Nitrogen: The Essential Element. N2 is a molecule which is a gas at standard temperature and pressure.
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JonF Member (Idle past 194 days) Posts: 6174 Joined: |
I'm replying only to correct your errors Missed one: "N14 is a gas", and the deduction that there's no N14 in the soil 'cause it's all going back to the atmosphere.
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JonF Member (Idle past 194 days) Posts: 6174 Joined: |
It travels in a straight line for an inch or so before it loses its energy. Mean free path, right? Got a convenient reference for that? I couldn't dig it up on Google.
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PurpleYouko Member Posts: 714 From: Columbia Missouri Joined: |
If the alpha particle has not enough energy to penetrate a layer of skin it does not have the energy to cause fission unless it comes in contact with beryllium.
Alpha particles are not involved in the process of fission.Berylium is rather a special case. It is often used in nuclear reactors as a reflecting shield material as it helps a smaller mass of uranium to achieve criticality by sending neutrons back into the uranium. One note also on the term "Neutron Flux"What this actually means is the neutron density at a given point. When the flux reaches a certain level then a chain reaction will begin. In underground situations, the flux could be as low as one neutron every minute or so. In a small working reactor at 10MWatts (with highly enriched fuel), it is something like 2E14 neutrons/second. It isn't really appropriate to talk about flux in the Earth
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PurpleYouko Member Posts: 714 From: Columbia Missouri Joined: |
Mean free path, right? Got a convenient reference for that? I couldn't dig it up on Google.
Something like that. It all depends on the density of the surrounding material. In dense rock it is likely to hit something within an inch or two. In a reactor we only need a couple of centimeters or less of shielding to stop all the neutrons. They aren't good at penetrating stuff but they do one hell of a lot of damage to the stuff they hit. I don't have a ready source of information to reference. I'm just basing my information on what I have picked up over the last 6 years working at a research reactor. I will see if I can find something.
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PurpleYouko Member Posts: 714 From: Columbia Missouri Joined: |
Mean free path, right? Got a convenient reference for that? I couldn't dig it up on Google.
I managed to dig up a load of complex calculations about the mean free path of a thermal neutron through various materials. Not many real examples though.The defining factor is the density of the surrounding material and the probability of interactions between Neutron and Target. This is dependent on the Barns radius This is about the best explanation that I managed to find
quote: My earlier description of spontaneous fission as a potential cause for N15 to capture a neutron was a little simplistic.What actually happens is that a fast neutron is emitted by fission but this has way too much energy to be captured so it is likely to collide with other neclei in the vacinity and cause them to also fission. This secondary fission will release much lower energy (thermal) Neutrons which are able to be captured by the N14 (or any other nucleus) Often the resultant nucleus will be unstable or meta-stable and will quickly decay, releasing beta or alpha particles along with Gammas. Some of these may cause further reactions, possibly resulting in a thermal neutron (in the case of the Alpha colliding with a nucleus such as Beryllium). Each initial fission will most likely result in a cascade of minor nuclear reactions and could result in the production of many thermal neutrons which could potentially be the source of C14. The radius of such a cascade is probably still only in the region of a few inches from the initial fission.
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PurpleYouko Member Posts: 714 From: Columbia Missouri Joined: |
Missed one: "N14 is a gas", and the deduction that there's no N14 in the soil 'cause it's all going back to the atmosphere.
Not to be too picky but N2 is a gas. N14 is an atom and as such can be bonded to other atoms as part of a molecule.
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Percy Member Posts: 22492 From: New Hampshire Joined: Member Rating: 4.9 |
PurpleYouko writes: My earlier description of spontaneous fission as a potential cause for N15 to capture a neutron was a little simplistic.What actually happens is that a fast neutron is emitted by fission but this has way too much energy to be captured so it is likely to collide with other neclei in the vacinity and cause them to also fission. I have no first hand knowledge of these processes like you do, so I can only read about them. What I'm reading doesn't agree with how I'm interpreting your description, so maybe I'm misinterpreting something. By "spontaneous fission" are you referring to radioactive decay? If so, then if we consider the example of 238U, when it decays to 234Th it gives off an alpha particle, not a fast neutron, or at least that's what I'm reading. I'm also reading that neutron sources use indirect means to produce the neutrons, for example, mixing 241Am with Beryllium so that the alpha particles from the Americium strike the Beryllium and create a 12C atom plus a neutron. So what's the story? --Percy
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crashfrog Member (Idle past 1493 days) Posts: 19762 From: Silver Spring, MD Joined: |
I don't have a ready source of information to reference. I'm just basing my information on what I have picked up over the last 6 years working at a research reactor. OMG you work at the reactor! That's awesome, we're practically neighbors. I work at the Rollins Bottoms experiment station back behind the reactor sometimes. Down past the golf course.
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Coragyps Member (Idle past 761 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
So what's the story? Not all 238U decays through alpha particle emission. 0.00005% splits into two (sizable) nuclei and some neutrons instead.Go to http://atom.kaeri.re.kr/ton/nuc8.html and find 238U in the table - link at the top of the linked page.Other heavy nuclei have this fission pathway available as well - poke around anything heavier than lead on that site I linked and you'll see the "branch ratio" or amount that decays by a fission path. Look at radium 226 there - it has"Mode of decay: 14C Branch ratio: 3.2E-9 % Decay energy: 28.199 MeV" listed as a decay path. And 226Ra is in the 238U decay path, so there's always some around in the crust. Edited by Coragyps, : No reason given.
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