Radioactive dating time change

Nuclear Chemistry

Nuclear equations are typically written in the format shown below. There are 5 different types of radioactive decay.

Where A is the parent isotope (the atom being broken apart) B is the daughter isotope or the isotope formed. When an element is broken down in alpha decay it looses two neutrons and two (2) protons. This means that the name of the element will change as well, moving back two (2) places on the periodic table. Alpha decay is not very penetrating because the He atoms capture electrons before traveling very far. However it is very damaging because the alpha particles can knock atoms off of molecules. Alpha decay is the most common in elements with an atomic number greater than 83.

The beta emission increases the atomic number by one (1) by adding one (1) proton. At the same time, one (1) neutron is lost so the mass of the daughter isotope is the same as the parent isotope. Beta negative decay is more penetrating than alpha decay because the particles are smaller, but less penetrating than gamma decay. Beta electrons can penetrate through about one (1) cm of flesh before they are brought to a halt because of electrostatic forces. Beta decay is most common in elements with a high neutron to proton ratio.

In gamma emission, neither the atomic number or the mass number is changed. A high energy gamma ray is given off when the parent isotope falls into a lower energy state. Gamma radiation is the most penetrating of all. These photons can pass through the body and cause damage by ionizing all the molecules in their way.

Positron emission (also called Beta positive decay) follows the form:

In this reaction a positron is emitted. A positron is exactly like an electron in mass and charge force except with a positive charge. It is formed when a proton breaks into a neutron with mass and neutral charge and this positron with no mass and the positive charge. Positron emission is most common in lighter elements with a low neutron to proton ratio.

In this reaction a nucleus captures one (1) of its own atom's inner shell electrons which reduces the atomic number by one. This captured electron joins with a proton in the nucleus to form a neutron. Electron capture is common in larger elements with a low neutron to proton ratio.

All elements with an atomic number over 83 are considered radioactive. Radioactivity can be measured using a geiger counter, a cylinder containing a low-pressure gas and two (2) electrodes. Radiation ionizes the atoms in the cylinder and allows current to flow between the electrodes.

All radioactive elements disintegrate according to their specific half life. The half life of a radioactive substance is the time required for half of the initial number of nuclei to disintegrate. The decay rate expresses the speed at which a substance disintegrates. The following equation represents the relationship between the number of nuclei remaining, N, the number of nuclei initially present, N0, the rate of decay, k, and the amount of time, t.

The relationship between the half-life of a radioactive substance and k, the rate at which it decays can also be found.

By using these equations, it is possible to calculate how much of a nuclear substance will be left after a certain time and how much of a substance originally existed. A common example is isotopic dating in which the ages of archeological artifacts are determined by measuring the activity of the isotopes.

Last Update: Wednesday, 27-Mar-2002 07:21:10 EST

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Radioactive dating time change

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Carbon 14 is in equilibrium


How is Carbon 14 used to date specimens and artifacts?

Page 3

  • Limitations of the Historical Sciences

Carbon 14 Dating is based on Assumptions


The Assumptions used in Carbon 14 Dating


Has the C-14/C-12 ratio (equilibrium) always been constant?

Page 4

  • Factors that could have affected past C-14 levels

Geomagnetic Field Intensity

Page 5

  • Is there any Data That Would Support the Above Assumptions of a global flood?


C-14 Age Profile of Ancient Sediment and Peat Accumulations

Page 6

    • Does Coal have a residual level of C-14 left from before the Flood?


  • Carbon-14 Content of Fossil Carbon by Paul Giem

A lot of interesting things happen in the upper atmosphere of our world. Much of the high energy photons of the electromagnetic spectrum is filtered out by the time light gets to the surface of the earth: However, in the extreme upper atmosphere there are photons striking the atmosphere of such high energy that they initiate reactions of molecules or even change the nature of atoms themselves.

Ultraviolet light is responsible for initiating chemical reactions through a process called photodissociation. Molecules are torn apart by the energy of the ultraviolet photon. Once the atoms are separated they can then come back together again; possibly, the atoms can form different combinations, thus allowing new molecules to be produced. Ozone is produced in this way, it is produced by the photodissociation of Oxygen. Oxygen is produced from the photodissociation of water. Some have judged that as much as 25% of the Oxygen in our world could come from reactions occurring in the upper atmosphere.

If this large production of Oxygen in the upper atmosphere is a reality, then the reducing atmosphere postulated by evolutionists to allow for the generation of biological molecules, would be in jeopardy. It is interesting to note that the rocks in the precambrian contain metal oxides. The rocks are not found in a reduced state.

Cosmic rays, which contain even higher levels of energy than ultraviolet light, cause some of the atoms in the upper atmosphere to fly apart into pieces. Neutrons that come from these fragmented molecules run into other molecules. When a neutron collides into a Nitrogen 14 atom, the Nitrogen 14 turns into Carbon 14 (A proton is also produced in the reaction as can be seen in the graphic to the left.). So in this reaction, a neutron is captured by the Nitrogen Atom and a proton is released. Thus in the Nitrogen Atom, a proton is effectively converted into a neutron, which allows a Carbon to be produced.

Two other reactions (Oxygen 17 reacting with neutrons, and He 4 reacting with Carbon 13) both produce Carbon 14, but with much smaller yields. It has been estimated that about 21 pounds of Carbon 14 is produced every year in the upper atmosphere.

So in addition to Carbon 12 and Carbon 13, which are both naturally occurring, Carbon 14 is also naturally occurring in our world. However, unlike both Carbon 12 and 13, Carbon 14 is unstable. The only reason why Carbon 14 continues to be found on Earth is because of its continued production in the upper atmosphere.

If Carbon 14 is being produced in the upper atmosphere by cosmic ray bombardment at a constant rate, then carbon 14 must be accumulating in the world. Well, that would be the case if Carbon 14 wasn't unstable and degrading just as fast. It turns out that the production and degradation of Carbon 14 is going on at the same rate. The two reactions are at equilibium or nearly at equilibrium.

This Carbon 14/Nitrogen 14 equilibrium does not only exist in the upper atmosphere where Carbon 14 is produced. Winds cause the Carbon 14 to be carried throughout the world. In addition most of the Carbon 14 reacts with Oxygen to produce atmospheric CO2. Because CO2 gets incorporated into trees and plants, the plants also possess the same levels of Carbon 14 as in the atmosphere. The food that we eat is also contaminated with the same level of Carbon 14. So essentially the whole Biosphere contains Carbon 14 at the same equilibrium concentration. This equilibrium is true for most of the Biosphere except for marine environments. More will be said on this later.

Any animal or plant will contain the Biosphere level of Carbon 14. We for example ingest food containing Carbon 14 and we also defecate wastes containing Carbon 14. In addition Carbon 14 is also reconverting back into Nitrogen 14 in our bodies. Only when one dies is this process disrupted. At death there is no further ingestion of Carbon 14, so the Carbon 14 concentration will slowly decrease as individual Carbon 14 atoms degrade back into Nitrogen 14 atoms.

How is Carbon 14 used to date specimens and artifacts?

If it can be assumed that the concentration of Carbon 14 has always been at equilibrium at the same level as it is today, or we are able to produce radiocarbon calibration curves which would determine fluctuations in the C14 Concentration through time; then, we can use this assumption to determine how long ago a specimen was separated from the dynamic Biosphere.

(We will simplify the problem by not using any of the calibration curves. So for the sake of our discussion, we will assume that C14 concentration in the atmosphere has always been the same through time.)

Any animal or plant, continually exchanges organic molecules (Carbon containing molecules) with the environment. So all living organisms will contain the Biosphere level of Carbon 14. However, once an organism dies, and is somehow buried, the exchange of Carbon stops. As a consequence, the level of Carbon 14 in the buried carcass decreases according to the rate at which Carbon 14 degrades into Nitrogen 14 within the body.

When Scientists uncover fossils and other artifacts that contain Carbon, they can determine how long that sample was buried by determining the amount of Carbon 14 that has been lost since it was buried in the ground. They know the level of Carbon 14 in the Biosphere (assuming it hasn't changed), and they can measure the level of Carbon 14 in the specimen so what they do is determine the difference. That difference represents the loss in Carbon 14 that the specimen experienced while it was in the ground. Now all the scientist has to do is determine how many half-lives the loss represents. The number of half-lives will then give a number showing how long the sample was isolated from the biosphere. Below is a graph showing the loss that four different specimens would experience before being recovered for measurement.

Looking at the chart above, Sample D has 1/2 the radioactive Carbon 14 that was expected if that sample was part of the Biosphere. 1/2 the normal level of Carbon 14 indicates that Sample D has been buried for one half-life or 5730 years.

Sample C has 1/4 the radioactive Carbon 14 which indicates that it has been buried for two half-lives or 11460 years. Sample B has 1/8 the radioactive Carbon 14 indicating that it was buried for three half-lives or 17190 years. Finally, Sample A has 1/128 the radioactive Carbon 14 indicating that it was buried for seven half-lives or 40110 years.

In real life there are fluctuations in the Biosphere Carbon 14 levels through time that must be accounted for in the calculation. Also all Carbon 14 dates must be in reference to the total amount of Carbon (Carbon 12) found in the sample. The normal ratio of Carbon 14 to Carbon 12 as found in our present Biosphere is: 1 to 848,000,000,000. The radiation is actually quite small. There are only 13.6 disintegrations per gram of Carbon per min. Any loss of Carbon 14 would result in much smaller ratios and disintegrations of Carbon 14 atoms. One gram of carbon that originally averaged 13.6 disintegrations per minute, would average only 0.00166 disintegrations per minute after 13 half-lives (75,000 years). That is the same as 0.0996 disintegrations per hour or 2.39 disintegrations per day!

It is amazing how such small levels of radiation can be detected. But with the nuclear accelerator mass spectrometry technique which directly counts C14 atoms, it is still possible to detect samples that have undergone as many as 13 half-lives (75,000 years) of Carbon 14 degradation.

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