All matter is composed of atoms, which are in turn composed of a nucleus made of positively charged particles (protons) and particles with a neutral charge (neutrons) orbited by a cloud of electrons. Here’s an example:
The number of protons determines what element it is. In our example above there are two protons and two neutrons, so we can flip over to our periodic table and look for an element with an atomic number of 2 (atomic number = number of protons) and in doing so we can see that this is a helium atom.
Each element can have a given number of isotopes, which are atoms that have the same number of protons but a different number of neutrons. As an example, here’s an isotope of helium.
Notice that while the number of neutrons has changed this is still a helium atom because it still has two protons. This will become important later.
Atoms that are radioactive are unstable, so they throw off particles until they reach a more stable state (see Beta Decay Doodle). As the nucleus loses neutrons the atom can become a different isotope, as it loses protons the atom actually becomes a different element. We call this loss of particles “radioactive decay”, the original element is called the “parent”, while the new more stable form is called the “daughter”.
I really can’t stress enough that this is a very simplistic explanation of a very complicated process. If you want to get into exactly how or precisely why atoms and their particles behave this way you start getting into strong and weak nuclear forces and everybody starts to get headaches. That being said, the average decay rate is governed by those forces and, as such, is known. There’s no mechanism we know of that can actually alter these decay rates significantly. . .unless you drop a particularly unstable isotope into the center of, say, a very large star and strip off all it’s electrons. However, the decay rate for every isotope of every atom is unique, which means that if all of this were based on assumptions we wouldn’t expect different radiometric dating methods to reach the same results, which they consistently do.
Additionally, if radiometric dating isn’t reliable we certainly wouldn’t expect for radiometric dates to line up with non-radiometric dates derived from things like tree rings and varves but, again, they consistently do.
Further reading material on radiometric dating:
- Radiometric Dating: A Christian Perspective
- Age Correlations and an Old Earth
- Why Radiocarbon Dating Works – Lake Suigetsu
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