Grains, seeds, nutshells, grasses, twigs, cloth, paper, hide, burnt bones, organic material mixed with soil charcoal & wood charred bones
Source 3
Radioactivity: Spontaneous changes in a nucleus accompanied by the emission of energy from the nucleus as a radiation.
Radioactive Half-Life: A period of time in which half the nuclei of a species of radioactive substance would decay.
We imagine that we have a radioactive substance. When the nuclei of the substance decay, they emit radiation (alpha, beta, or gamma rays) that can be detected by counters such as a Geiger Counter. For a Geiger Counter, each time an emitted particle passes through the Geiger Counter, the counter makes a clicking sound. The number of clicks per unit time of the counter tells us how many decays per unit time are occurring. But the rate of clicks decreases with time because the rate is directly proportional to the number of radioactive nuclei in the substance that can decay. Hence, as time goes on, we know that the number of radioactive nuclei in the substance must also be decreasing.
The radioactive half-life of the substance is the period of time over which the number of radioactive nuclei decreases by a factor of one-half.
Radioactive decay is a quantum mechanical process governed by probability waves. In a short period of time, each radioactive nucleus has a certain probability of decaying, but whether it actually does is determined by random chance. In the animation, we plot the number of remaining un-decayed nuclei as time goes on. There is some irregularity introduced into this plot by the quantum randomness. When the animation repeats itself, you will see that it does not happen the second time in exactly the way it did the first time.
Source 4
There are five main problems with this instrumental technique:
If the sample died more than 50,000 years ago, it would have no measurable C14 left today. Thus, the analysis technique cannot differentiate between samples which are 50 millennia or 100 millennia BP.
The ratio of C-14 to Carbon-12 in living matter has not been absolutely constant over the past 50,000 years:
The ratio was higher before the industrial era started to release large amounts of carbon dioxide into the atmosphere. The measured age of any samples which died after the start of industrialization circa 1850 would appear older than they really are. This, of course, would not affect the C-14 dating of the shroud of Turin, which is the subject of hot debate between some scientists (who believe that the shroud was created in medieval times) and some conservative Christians (who believe that the shroud was used in Jesus' burial and thus is dated to the 1st century ).
Testing nuclear bombs in the atmosphere in the 1950s increased the amount of C-14 in atmospheric carbon dioxide. The measured age of samples that were living during that time would appear younger than they really are. This has no impact on the dating of the Shroud of Turin or on material from biblical times either.
The quantity of cosmic rays bombarding the earth affects the amount of C-14 that is created in the upper atmosphere. The level of cosmic rays varies with the sun's activity, the strength of the Earth's magnetic field, and any magnetic clouds traversed by the solar system as it proceeds around our galaxy.
This means that the C-14 to C-12 ratio in a sample might be slightly higher or lower at the time that it died than the present value. Thus it was necessary to calibrate the technique. Samples whose ages are known are measured using C-14 dating, and a calibration curve was created. This makes minor corrections to the measured age, producing a more accurate answer than would be obtained by using the theoretical calculations alone.
Libby's original estimate of the t 1/2 of C-14 was slightly in error at 5,568 years. This means that date estimates made in the very early years of the technique were 3% low.
The C-14 dating system assumes that C-14 in the animal or plant matches the level in the general environment. In rare cases, plants and animals may live in very unusual environments whose C-14 content is much lower than what one would expect. This is called a "reservoir effect." For example:
It is possible for snails to live in water that contains carbon leached out of ancient limestone which has no measurable C-14 left. As a result, the snails' shells will also be deficient in C-14 and test older than their true age.
In a few areas of the world, seals dine on fish that in turn had eaten other fish and plants that lived in sea water that has been traveling along the bottom of the ocean for thousands of years, gradually losing its C-14 content. Again, the quantity of C-14 in their environment is deficient. They would also test older than they really are.
According to EvoWiki.org: "The problem caused by the reservoir effect is well known by archaeologists, geologists, and anybody else who use radiocarbon dates; they test for it and take it into account when interpreting radiocarbon data."
Contamination of the sample can include sufficient C-14 to make it seem newer than it really is. Porous samples can contain recently living material with a full "charge" of C-14. Sample cleaning and proper laboratory technique are critical.
