Carbon - Windows to the Universe
Advanced Theories of Covalent Bonding . Electron capture occurs when one of the inner electrons in an atom is captured by . The radioactivity of carbon provides a method for dating objects that were a part of a living organism. Along with stable carbon, radioactive carbon is taken in by plants and animals. Accelerator mass spectrometry (AMS) dating is an advanced technique used to lose the electrons and emerge as the triple, positively charged carbon atoms. carbon 14 atoms in the sample but also the quantity of carbon 12 and carbon Beginner · Intermediate · Advanced · Become a The 14C nucleus has 6 protons plus 8 neutrons, giving it an atomic mass of Most carbon atoms also have 6 neutrons, giving them an atomic mass of 12 (= 6 protons + 6 neutrons). via a technique called "carbon dating" or "radiocarbon dating".
The two requirements for varves to be useful in dating are 1 that sediments vary in character through the seasons to produce a visible yearly pattern, and 2 that the lake bottom not be disturbed after the layers are deposited. These conditions are most often met in small, relatively deep lakes at mid to high latitudes. Shallower lakes typically experience an overturn in which the warmer water sinks to the bottom as winter approaches, but deeper lakes can have persistently thermally stratified temperature-layered water masses, leading to less turbulence, and better conditions for varve layers.
Varves can be harvested by coring drills, somewhat similar to the harvesting of ice cores discussed above. Overall, many hundreds of lakes have been studied for their varve patterns. Each yearly varve layer consists of a mineral matter brought in by swollen streams in the spring. Regular sequences of varves have been measured going back to about 35, years.
The thicknesses of the layers and the types of material in them tells a lot about the climate of the time when the layers were deposited. For example, pollens entrained in the layers can tell what types of plants were growing nearby at a particular time.
Other annual layering methods. Besides tree rings, ice cores, and sediment varves, there are other processes that result in yearly layers that can be counted to determine an age. Annual layering in coral reefs can be used to date sections of coral. Coral generally grows at rates of around 1 cm per year, and these layers are easily visible. As was mentioned in the uranium-series section, the counting of annual coral layers was used to verify the accuracy of the thorium method.
There is a way of dating minerals and pottery that does not rely directly on half-lives. Thermoluminescence dating, or TL dating, uses the fact that radioactive decays cause some electrons in a material to end up stuck in higher-energy orbits.
The number of electrons in higher-energy orbits accumulates as a material experiences more natural radioactivity over time. If the material is heated, these electrons can fall back to their original orbits, emitting a very tiny amount of light.
If the heating occurs in a laboratory furnace equipped with a very sensitive light detector, this light can be recorded. The term comes from putting together thermo, meaning heat, and luminescence, meaning to emit light. By comparison of the amount of light emitted with the natural radioactivity rate the sample experienced, the age of the sample can be determined. TL dating can generally be used on samples less than half a million years old.
TL dating and its related techniques have been cross calibrated with samples of known historical age and with radiocarbon and thorium dating. While TL dating does not usually pinpoint the age with as great an accuracy as these other conventional radiometric dating, it is most useful for applications such as pottery or fine-grained volcanic dust, where other dating methods do not work as well. Electron spin resonance ESR.
Carbon 14 dating 1
Also called electron paramagnetic resonance, ESR dating also relies on the changes in electron orbits and spins caused by radioactivity over time. However, ESR dating can be used over longer time periods, up to two million years, and works best on carbonates, such as in coral reefs and cave deposits. It has also seen extensive use in dating tooth enamel. This dating method relies on measuring certain isotopes produced by cosmic ray impacts on exposed rock surfaces.
Because cosmic rays constantly bombard meteorites flying through space, this method has long been used to date the ' flight time' of meteorites--that is the time from when they were chipped off a larger body like an asteroid to the time they land on Earth.
The cosmic rays produce small amounts of naturally-rare isotopes such as neon and helium-3, which can be measured in the laboratory.
The cosmic-ray exposure ages of meteorites are usually around 10 million years, but can be up to a billion years for some iron meteorites. In the last fifteen years, people have also used cosmic ray exposure ages to date rock surfaces on the Earth. This is much more complicated because the Earth's magnetic field and atmosphere shield us from most of the cosmic rays.
Cosmic ray exposure calibrations must take into page 19 account the elevation above sea level because the atmospheric shielding varies with elevation, and must also take into account latitude, as the magnetic shielding varies from the equator to the poles.
Nevertheless, terrestrial cosmic-ray exposure dating has been shown to be useful in many cases. We have covered a lot of convincing evidence that the Earth was created a very long time ago.
The agreement of many different dating methods, both radiometric and non-radiometric, over hundreds of thousands of samples, is very convincing. Yet, some Christians question whether we can believe something so far back in the past. My answer is that it is similar to believing in other things of the past. It only differs in degree. Why do you believe Abraham Lincoln ever lived? Because it would take an extremely elaborate scheme to make up his existence, including forgeries, fake photos, and many other things, and besides, there is no good reason to simply have made him up.
Well, the situation is very similar for the dating of rocks, only we have rock records rather than historical records. There are well over forty different radiometric dating methods, and scores of other methods such as tree rings and ice cores.
Carbon 14 dating 1 (video) | Khan Academy
All of the different dating methods agree--they agree a great majority of the time over millions of years of time. Some Christians make it sound like there is a lot of disagreement, but this is not the case. The disagreement in values needed to support the position of young-Earth proponents would require differences in age measured by orders of magnitude e. The differences actually found in the scientific literature are usually close to the margin of error, usually a few percent, not orders of magnitude!
Vast amounts of data overwhelmingly favor an old Earth. Several hundred laboratories around the world are active in radiometric dating. Their results consistently agree with an old Earth. Over a thousand papers on radiometric dating were published in scientifically recognized journals in the last year, and hundreds of thousands of dates have been published in the last 50 years.
Essentially all of these strongly favor an old Earth. Radioactive decay rates have been measured for over sixty years now for many of the decay clocks without any observed changes. And it has been close to a hundred years since the uranium decay rate was first determined. Both long-range and short-range dating methods have been successfully verified by dating lavas of historically known ages over a range of several thousand years. The mathematics for determining the ages from the observations is relatively simple.
The last three points deserve more attention. Some Christians have argued that something may be slowly changing with time so all the ages look older than they really are. The only two quantities in the exponent of a decay rate equation are the half-life and the time. So for ages to appear longer than actual, all the half-lives would have to be changing in sync with each other. One could consider that time itself was changing if that happened remember that our clocks are now standardized to atomic clocks!
Beyond this, scientists have now used a "time machine" to prove that the half-lives of radioactive species were the same millions of years ago. This time machine does not allow people to actually go back in time, but it does allow scientists to observe ancient events from a long way away. The time machine is called the telescope.
Because God's universe is so large, images from distant events take a long time to get to us. Telescopes allow us to see supernovae exploding stars at distances so vast that the pictures take hundreds of thousands to millions of years to arrive at the Earth.
When the organism dies, this exchange stops; as the carbon undergoes radioactive decay, the ratio drops. By measuring the ratio, the age can be determined.How Carbon Dating Works
Figure Figure Radiocarbon Dating View More Figure Radiocarbon Dating Plants take up radioactive carbon formed in the atmosphere. The radioactive carbon then enters the food chain. So long as a plant or animal is alive, the amount of carbon remains constant.
Once the life form is dead, the carbon can only decay, though it takes several hundred years for the decay to be measurable. So let me draw the Earth.
So let me just draw the surface of the Earth like that. It's just a little section of the surface of the Earth. And then we have the atmosphere of the Earth. I'll draw that in yellow. So then you have the Earth's atmosphere right over here. Let me write that down, atmosphere. And I'll write nitrogen. Its symbol is just N.
And it has seven protons, and it also has seven neutrons. So it has an atomic mass of roughly Then this is the most typical isotope of nitrogen. And we talk about the word isotope in the chemistry playlist. An isotope, the protons define what element it is.
But this number up here can change depending on the number of neutrons you have. So the different versions of a given element, those are each called isotopes. I just view in my head as versions of an element. So anyway, we have our atmosphere, and then coming from our sun, we have what's commonly called cosmic rays, but they're actually not rays.
You can view them as just single protons, which is the same thing as a hydrogen nucleus. They can also be alpha particles, which is the same thing as a helium nucleus.
And there's even a few electrons. And they're going to come in, and they're going to bump into things in our atmosphere, and they're actually going to form neutrons. So they're actually going to form neutrons. And we'll show a neutron with a lowercase n, and a 1 for its mass number. And we don't write anything, because it has no protons down here. Like we had for nitrogen, we had seven protons.
So it's not really an element. It is a subatomic particle. But you have these neutrons form. And every now and then-- and let's just be clear-- this isn't like a typical reaction. But every now and then one of those neutrons will bump into one of the nitrogen's in just the right way so that it bumps off one of the protons in the nitrogen and essentially replaces that proton with itself. So let me make it clear. So it bumps off one of the protons. So instead of seven protons we now have six protons.
But this number 14 doesn't go down to 13 because it replaces it with itself.