The great scientist Ernest Rutherford was the first to define the concept of “half-life,” that is, the time it takes for one half of the atoms in a given quantity of a radioactive element (such as plutonium) to decay into another element (such as uranium), or for one isotope of an element (such as carbon-14) to decay into another isotope of that same element (such as carbon-12).Moreover, Rutherford and all scientists since him have declared that the radioactive decay of a given element or isotope occurs “at a specific, universal, immutable rate” (Castelvecchi 2008: 21).This decay is an example of an exponential decay, shown in the figure below.Knowing about half-lives is important because it enables you to determine when a sample of radioactive material is safe to handle.The half-life of Carbon 14, that is, the amount of time it takes for half of any amount of Carbon 14 to decay, is approximately 5730 years.
And as far as we know, it has been forming in the earth’s upper atmosphere since the atmosphere was made back on Day Two of Creation Week (part of the expanse, or firmament, described in Genesis 1:6–8). Cosmic rays from outer space are continually bombarding the upper atmosphere of the earth, producing fast-moving neutrons (subatomic particles carrying no electric charge) (Figure 1a).1 These fast-moving neutrons collide with atoms of nitrogen-14, the most abundant element in the upper atmosphere, converting them into radiocarbon (carbon-14) atoms.
It then takes the same amount of time for half the remaining radioactive atoms to decay, and the same amount of time for half of those remaining radioactive atoms to decay, and so on. The amount of time it takes for one-half of a sample to decay is called the half-life of the isotope, and it’s given the symbol: It’s important to realize that the half-life decay of radioactive isotopes is not linear.
For example, you can’t find the remaining amount of an isotope as 7.5 half-lives by finding the midpoint between 7 and 8 half-lives.
Based on this assumption, scientists use the decay rate of certain substances to date the age of rock formations, fossils, and the Earth itself.
reported that, “when researchers suggested in August  that the sun causes variations in the decay rates of isotopes of silicon, chlorine, radium and manganese, the physics community reacted with curiosity, but mostly with skepticism” (Ibid.).