First of all, it's predicated upon a set of questionable assumptions. Carbon dating is a technique used to determine the approximate age of once-living materials. This fossil fuel effect also known as the Suess effect, after Hans Suess, who first reported it in would only amount to a reduction of 0. Isn't beta decay controlled by the weak force? Subsequently, these dates were criticized on the grounds that before the scrolls were tested, they had been treated with modern castor oil in order to make the writing easier to read; it was argued that failure to remove the castor oil sufficiently would have caused the dates to be too young. How do they know, then, what time it is and how to be properly elongated?
When a creature dies, it ceases to consume more radiocarbon while the C already in its body continues to decay back into nitrogen. So, if we find the remains of a dead creature whose C to C ratio is half of what it's supposed to be that is, one C atom for every two trillion C atoms instead of one in every trillion we can assume the creature has been dead for about 5, years since half of the radiocarbon is missing, it takes about 5, years for half of it to decay back into nitrogen.
If the ratio is a quarter of what it should be one in every four trillion we can assume the creature has been dead for 11, year two half-lives. After about 10 half-lives, the amount of radiocarbon left becomes too miniscule to measure and so this technique isn't useful for dating specimens which died more than 60, years ago.
Another limitation is that this technique can only be applied to organic material such as bone, flesh, or wood.
It can't be used to date rocks directly. Carbon Dating - The Premise Carbon dating is a dating technique predicated upon three things: The rate at which the unstable radioactive C isotope decays into the stable non-radioactive N isotope, The ratio of C to C found in a given specimen, And the ratio C to C found in the atmosphere at the time of the specimen's death.
Carbon Dating - The Controversy Carbon dating is controversial for a couple of reasons.
First of all, it's predicated upon a set of questionable assumptions. We have to assume, for example, that the rate of decay that is, a 5, year half-life has remained constant throughout the unobservable past. However, there is strong evidence which suggests that radioactive decay may have been greatly accelerated in the unobservable past.
We also know that the ratio decreased during the industrial revolution due to the dramatic increase of CO 2 produced by factories. This man-made fluctuation wasn't a natural occurrence, but it demonstrates the fact that fluctuation is possible and that a period of natural upheaval upon the earth could greatly affect the ratio. Volcanoes spew out CO 2 which could just as effectively decrease the ratio. Specimens which lived and died during a period of intense volcanism would appear older than they really are if they were dated using this technique.
The ratio can further be affected by C production rates in the atmosphere, which in turn is affected by the amount of cosmic rays penetrating the earth's atmosphere. The amount of cosmic rays penetrating the earth's atmosphere is itself affected by things like the earth's magnetic field which deflects cosmic rays. Precise measurements taken over the last years have shown a steady decay in the strength of the earth's magnetic field.
But carbon is slightly radioactive: Why doesn't the carbon in the air decay along with terrestrial carbon? The trick is that radioactive carbon is continually replenished in a complex reaction that involves high-energy cosmic rays striking the upper atmosphere.
In this process, nitrogen 7 protons and 7 neutrons gains a neutron and loses a proton, producing carbon 6 protons and 8 neutrons. The proportion of carbon to carbon in the atmosphere therefore remains relatively stable at about 1. One of the implied assumptions in radiocarbon dating is that levels of atmospheric carbon have remained constant over time.
This turns out not to be exactly true, and so there is an inherent error between a raw "radiocarbon date" and the true calendar date. To correct for this, scientists have compared radiocarbon dates from objects who's age is known by other means, such as artifacts from Egyptian tombs, and growth rings from ancient trees.
In this way, calibration tables have been developed that eliminate the discrepancy. Despite its usefulness, radiocarbon dating has a number of limitations. First, the older the object, the less carbon there is to measure.
Radiocarbon dating is therefore limited to objects that are younger than 50, to 60, years or so. Since humans have only existed in the Americas for approximately 12, years, this is not a serious limitation to southwest archaeology. Radiocarbon dating is also susceptible to contamination. If the ground in which an object is buried contains particles of coal or other ancient sources of carbon, radiocarbon testing may indicate that the object is far older than it really is.
Conversely, contamination by newer plant matter carried by flowing water or intruding plant roots may result in a date that is much too young.