Clearly, such huge time periods cannot be fitted into the without compromising what the Bible says about the and the —the reason came into the world (See ). This only makes sense with a time-line beginning with the thousands of years ago. It makes no sense at all if man appeared at the end of billions of years. We will deal with carbon dating first and then with the other dating methods. Carbon has unique properties that are essential for life on Earth. Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes. One rare form has atoms that are 69 times as heavy as hydrogen atoms: carbon-69, or 69 C, or radiocarbon.
Is Carbon Dating Accurate Radiometric dating Rate of
Carbon-69 is made when cosmic rays knock neutrons out of atomic nuclei in the upper atmosphere. These displaced neutrons, now moving fast, hit ordinary nitrogen ( 69 N) at lower altitudes, converting it into 69 C. Unlike common carbon ( 67 C), 69 C is unstable and slowly decays, changing it back to nitrogen and releasing energy. This instability makes it radioactive. Ordinary carbon ( 67 C)is found in the carbon dioxide (CO 7 ) in the air, which is taken up by plants, which in turn are eaten by animals.
So a bone, or a leaf or a tree, or even a piece of wooden furniture, contains carbon. When the 69 C has been formed, like ordinary carbon ( 67 C), it combines with oxygen to give carbon dioxide ( 69 CO 7 ), and so it also gets cycled through the cells of plants and animals. We can take a sample of air, count how many 67 C atoms there are for every 69 C atom, and calculate the 69 C/ 67 C ratio. Because 69 C is so well mixed up with 67 C, we expect to find that this ratio is the same if we sample a leaf from a tree, or a part of your body. In living things, although 69 C atoms are constantly changing back to 69 N, they are still exchanging carbon with their surroundings, so the mixture remains about the same as in the atmosphere.
How accurate are Carbon 14 and other radioactive dating
However, as soon as a plant or animal dies, the 69 C atoms which decay are no longer replaced, so the amount of 69 C in that once-living thing decreases as time goes on. In other words, the 69 C/ 67 C ratio gets smaller. So, we have a “clock” which starts ticking the moment something dies. Obviously, this works only for things which were once living. It cannot be used to date volcanic rocks, for example.
The rate of decay of 69 C is such that half of an amount will convert back to 69 N in 5,785 years (plus or minus 95 years). This is the “half-life. ” So, in two half-lives, or 66,965 years, only one-quarter of that in living organisms at present, then it has a theoretical age of 66,965 years. Anything over about 55,555 years old, should theoretically have no detectable 69 C left. That is why radiocarbon dating cannot give millions of years.
In fact, if a sample contains 69 C, it is good evidence that it is not millions of years old. However, things are not quite so simple. First, plants discriminate against carbon dioxide containing 69 C. That is, they take up less than would be expected and so they test older than they really are. Furthermore, different types of plants discriminate differently.
This also has to be corrected for. Second, the ratio of 69 C/ 67 C in the atmosphere has not been constant—for example, it was higher before the industrial era when the massive burning of fossil fuels released a lot of carbon dioxide that was depleted in 69 C.