The notion that the earth is millions of years old is based on radiometric dating. Radiometric dating is a method to estimate the age of rocks based on concentrations of different elements or different isotopes in the rocks. This method is based on radioactive decay and will now be explained. The first thing to know is that there are assumptions made in these calculations. The answer of the calculations is the age of the rocks is only true if the assumptions used in the calculations are true. In radiometric dating there are ‘parent’ atoms and ‘daughter’ atoms very much like carbon-14 is the parent to the daughter carbon-12 used in carbon dating. There are five basic assumptions used in radiometric dating. The first two are that the amount of the parent and the amount of daughter atoms is known during the starting conditions. Since this is when the rocks were formed no one knows and we are guessing. Certainly they were not measured ‘millions’ of years ago so there is an assumption for the starting conditions. The third assumption is that the rates of decay from one element to another or from one isotope to another has always been constant. Again, these rates of decay could not have been measured in the remote past and we only know the current decay rates for certain. The fourth and fifth assumptions are that no parent and no daughter elements or isotopes have been added or lost throughout the history of the rock. The processes that can add and remove isotopes and elements are leaching and contamination. Both leaching and contamination are known to occur. It is assumed that the amount of both leaching and contamination has been so small that these do not significantly affect the calculation. These five assumptions are disputed by creationist’s who have valid arguments about the accuracy and truth of radiometric dating.
The first radioisotope dating method that was extensively studied was the decay of Uranium-238. This became the basis for all other radiometric dating. Uranium-238 is an unstable atom and will change in lead-206. There are several steps in this process and each step is called decay as one atom turns into another atom. The way these change is well understood and the time it takes for these transitions is also known and is the basis for the dating estimates.
To begin the discussion of radioisotope dating let’s review the atom. The atom is the smallest chemical unit and these are the building blocks of creation. All materials are made up of atoms. Each atom has a nucleus and an electron cloud. In the nucleus of atoms are protons and neutrons. The electrons are far away from the nucleus and can be thought of as spinning in circles around the nucleus. They are actually not spinning in exact circles and the location of the electrons is described as being in certain electron clouds. Inside the nucleus the protons and neutrons are about the same size so both have an atomic mass of 1. The electrons are so small they have no atomic mass. The protons have a positive electrical charge, the neutrons have no charge, and the electrons have a negative electrical charge.
The Atom
The periodic table has all of the types of atoms, which are also called elements. Each element has an atomic symbol. For example C is for carbon, H is for hydrogen, and He is for helium. Each of the elements has a different number of protons in the nucleus. The atom with only one proton in the nucleus is hydrogen and its atomic symbol is H. The atom with two protons is the nucleus is helium with the atomic symbol He, and with 3 protons is lithium whose atomic symbol is Li. The number of protons in the nucleus is called the atomic number. So the atomic number of hydrogen is 1, helium is 2 and lithium is 3. The periodic table shows the atomic symbol for each element and the atomic number.
The other number for each element on the periodic table is the atomic mass. This is the combination of both the protons and the neutrons in the nucleus. For example hydrogen has only one proton and no neutrons, so the atomic number is 1 and the atomic mass is also one. Helium has 2 protons and 2 neutrons, so the atomic number is 2 and the atomic mass is 4. Carbon has 6 protons and 6 neutrons so the atomic number is 6 and the atomic mass is 12.
Isotopes and Atomic Decay
Sometimes an element will have a different number of neutrons than is listed in the periodic table. We saw this with carbon-14. Every carbon atom has 6 protons. Carbon usually has 6 neutrons and this is why the atomic mass is 12. This is called carbon-12. An isotope is when an element has a different number of neutrons in the nucleus. For example, carbon-14 has 8 neutrons rather than 6, so the atomic mass is 14 (8+6). This is called carbon-14 as explained in carbon dating. Isotopes of atoms are unstable and they will all eventually change into one of the stable atoms listed on the periodic table. There are different ways isotopes change into one of the stable elements. These changes are called atomic decay.
There are three types of atomic decay; alpha decay, beta decay and gamma decay. In all of these the parent atom decays into the daughter atom. In alpha decay the parent atom emits a helium nucleus. Since the helium nucleus contains 2 protons and two neutrons, the daughter of alpha decay will have an atomic number which is 2 less than the parent and an atomic mass that is 4 less than the parent. Another type of radioactive decay is beta decay. Here, one of the neutrons in the nucleus of the parent turns into a proton and an electron. This seems a little odd but it does obey the laws of physics. There is conservation of charge since there was no net charge with the neutron in the parent, and the net charge of a proton and an electron is also zero since the charge of a proton is 1 and the charge of an electron is negative 1. There is also conservation of energy which can be understood here as conservation of mass. The atomic mass of the neutron in the parent was 1. This became a proton with an atomic mass also of 1 and an electron with no atomic mass. In both alpha and beta decay the daughter is a different element than the parent since there are a different number of protons in the daughter represented by the new atomic number. The last form of atomic decay is gamma decay where the parent emits a gamma ray which is very high energy electromagnetic radiation. It is interesting that for every isotope of every element and every unstable atom there are only these three forms of atomic decay. This is all you need to know to understand radioactive decay. Uranium-238 only decays by alpha and beta decay. The decay of Uranium-238 is the basis of the belief that the earth is millions of years old. These dates are determined by measuring the ratios of some of the elements in the decay chain.
The decay of uranium-238 (U-238) involves many steps until it decays into the stable lead atom. The first step is when U-238 decays using alpha decay by emitting a helium nucleus. This will decrease the atomic number by 2 because the helium nucleus has 2 protons, so the daughter will not be uranium with 92 protons, it will be thorium with 90 protons. This is in the bottom row of the periodic table in the Actinide series. The atomic mass will change from 238 to 234 since the emitted helium nucleus had 2 protons and 2 neutrons. So in this first step U-238 becomes thorium-234 (Th-234) by alpha decay. The parent U-238 becomes the daughter Th-234. In alpha decay the daughter is a new element with 2 less protons so the atomic number is 2 less. The daughter also has 4 less particles in the nucleus so the atomic mass decreases by 4. In all the steps of radioactive decay the same pattern is always followed. U-238 always decays by alpha decay and never by beta or gamma decay. When an isotope of an element decays by beta decay, it always uses beta decay. These decay patterns are known and never change. That is why we can estimate how long it took to have certain ratios of the isotopes in materials such as rocks to estimate age.
The next step in the decay of U-238 is beta decay of TH-234 to protactimium-234 (Pa-234). In beta decay a neutron turns in to a proton and an electron. There is no net change in atomic mass or in electrical charge. Th-234 is on the bottom row of the periodic table in the Actinide series. Th-234 has 90 protons. After beta decay the daughter will have 91 protons and this is the next element to the right which is Pa-234. It is protactinium because it has 91 protons and it is Pa-234 because there are still 234 total protons and neutrons. The atomic mass does not change in beta decay, it is still 234.
When Pa-234 undergoes beta decay the daughter will be back to uranium with the change of another neutron into a proton. This will be U-234 rather than U-238 after one alpha and two beta decays. U-234 has alpha decay like U-238 did, and the daughter will be Th-230.
The process is the same for the remainder of the decay chain but the location in the periodic table will change. The actinide series in the bottom row of the periodic table contains elements with atomic number from 90 to 103. All of these ‘fit’ between the third and fourth element in the 7th row of the periodic table where the atomic number jumps from 89 to 104. The actinide series is taken out and displayed separately to keep the elements in the columns in the periodic table that have common chemical properties.
This is not particularly important for this discussion other than being able to follow the decay chain. The next step is alpha decay of Th-230 to radium-226 (R-226). Th-230 is at the beginning of the Actinide series and after alpha decay the atomic number will be 88. This is radium which is in the 7th row of the periodic table. When Ra-226 undergoes alpha decay the daughter is radon-222 (Rn-222). Radon has 86 protons and is at the end of the 6th row on the periodic table.
There are another 8 steps of the 14 steps in the Urainum-238 decay chain. Each step is either alpha decay or beta decay. The alpha decay decreases the protons by 2 and the beta decay increases the protons by 1. The number of protons is unique for each element so with both alpha and beta decay the daughter is a different element. In alpha decay the atomic mass decreases by 4 and in beta decay there is no change in the atomic mass. These steps can be followed until finally reaching the stable end product which is lead-206 (Pb-206).
Dating
The rate of decay from each of the elements is known and this is the half-life. The half-life of uranium-238 is very slow, 4.5 billion years. Some of it will decay quicker so there will be measurable amounts of the daughters much sooner. Many of the half-lives of elements in the U-238 decay chain are only days, minutes and seconds. The amounts of these elements in a rock can be measured very accurately. Scientists can measure the amount of U-238 and all the intermediates to lead-206. They use these amounts and the knowledge of half-lives to calculate age. They estimate how long it would take a certain amount of uranium to decay into a certain amount of lead.
Noah’s Flood and Leaching
The accuracy of this dating is dependent on the assumptions being correct. A significant assumption that cannot be proven is that the amount of the parent and daughter elements have never changed. It claims that none of the elements is the decay chain have ever been added or removed from the rock. The process that would add elements is contamination after migration of elements in layers, sections and grains within the rocks. Leaching removes elements and would greatly alter the dates. Both leaching and contamination can occur without visible evidence making it impossible to be certain of the amounts of uranium and lead, as well as all the intermediates, and so the estimated date is also uncertain. Anything that has happened to the earth’s crust to open these layers to the environment would create leaching and contamination. It is believed by creationists that during the time of Noah’s flood the earth was in such turmoil with catastrophic events such as volcanoes and earthquakes that massive leaching and contamination occurred in the earth’s crust which causes the radiometric dates to be inaccurate. With the global flood much of the daughter elements would be ‘washed ‘away. With less of them, measurements would indicate there has been less decay and the calculations based on these ratios would make the earth seem much older than it is. This assumption that no parent or daughter elements were ever added to the rocks is the basis of, and a requirement for radiometric dating to be accurate. It assumes the Bible is not true and that Noah’s flood never happened.
Another problem with dating is the huge discrepancies between different dating methods. The potassium-argon method is another common method used to obtain extremely old dates. We have some rocks on earth where the age is known after they form from volcanic lava flows. The volcano Hualalai in Hawaii erupted in 1800. The potassium-argon dates for these rocks range from 140 million years to 2.96 billion years in scientific literature published in 1968. Another volcano on Hawaii, Mt. Kilauea is thought to have erupted 200 years ago and the dates were calculated to be 12 million years old. These are some of many examples where we know radiometric dating gives a very inaccurate answer. While it is true that the earth being millions of years old is widely accepted it is important to know that it is not universally accepted and there are scientifically valid reasons to doubt this extremely old age. The earth may not be old enough to allow time for evolution to even be possible much less true, and even if the earth is this old it does not prove evolution is true, only that it may be true. The age of the earth is only one of the 50 controversies presented here.