It's accuracy has been verified by using C-14 to date artifacts whose age is known historically.

The fluctuation of the amount of C-14 in the atmosphere over time adds a small uncertainty, but contamination by "modern carbon" such as decayed organic matter from soils poses a greater possibility for error. Thomas Seiler, a physicist from Germany, gave the presentation in Singapore.

Although the time at which any individual atom will decay cannot be forecast, the time in which any given percentage of a sample will decay can be calculated to varying degrees of accuracy.

Symbolically, the process of *radioactive* decay can be expressed by the following differential equation, where N is the quantity of decaying nuclei and k is a positive number called the exponential decay constant.

The meaning of this equation is that the rate of change of the number of nuclei over time is proportional only to the number of nuclei.

Atoms of **radioactive** isotopes are unstable and decay over time by shooting off particles at a fixed rate, transmuting the material into a more stable substance.

For instance, half the mass of carbon-14, an unstable isotope of carbon, will decay into nitrogen-14 over a period of 5,730 years.

Recent puzzling observations of tiny variations in nuclear decay rates have led some to question the science behind carbon-14 **dating** and similar techniques.

However scientists tested the hypothesis that solar radiation might affect the rate at which *radioactive* elements decay and found no detectable effect.

The key is to measure an isotope that has had time to decay a measurable amount, but not so much as to only leave a trace remaining.

Given isotopes are useful for **dating** over a range from a fraction of their half life to about four or five times their half life.

The technique hinges on carbon-14, a **radioactive** isotope of the element that, unlike other more stable forms of carbon, decays away at a steady rate.