There are many ways that have been used to measure, determine or estimate how old the earth is. However, the age of the earth can never be proven scientifically. All of these methods involved calculations which are based on assumptions which can never be tested or proved. These assumptions include a uniform rate of decay, a closed system and zero initial daughter component. The assumptions themselves can never be proven to be valid, so the calculations based on these assumptions have some error.
Some of these estimates indicate the earth is as young as 5 to 10 thousand years old. This is consistent with the age of the earth from a literal interpretation of the Bible. Those who believe this use the scientific measurements that calculate the age of the earth as young and also question the truth of the assumptions used in the calculations that result in the earth being very old. The term ‘young earth creationists’ is used for those who believe the earth is about 7 thousand years old and interpret the creation story in the Bible literally.
Many of the estimates of the age of the earth calculate the age to be millions of years old. Since this is such a widely held belief it is important to understand that even if this is true it does not contradict the existence of God. It would just support a different interpretation of the Genesis account of creation, but that God is still the creator. If the earth is young evolution is not true, period. If the earth is old it does not prove evolution is true, it just allows enough time so it cannot be proven false. This is just one of the many controversies in the creation and evolution debate. If creation scientists are correct on any one of these, evolution is not true and there are many reasons to believe the earth is young.
Carbon Dating
The most common impression of the age of the earth estimates are based on carbon dating. It is a term many people have heard. However, carbon dating can never give an age of the earth in millions of years, only in thousands of years. The millions of year’s estimates are based on radiometric dating which is different. Here is the difference. Understanding carbon dating begins with the carbon atom. Carbon normally has a total of 12 protons and neutrons in the nucleus of the atom. A very small portion of carbon has a total of 14 protons and neutrons after events in the atmosphere with cosmic radiation. This is called carbon-14. So there is a normal ratio or proportion of carbon-14 to carbon-12 in the atmosphere. The carbon in the air is in the form of carbon dioxide. Carbon dioxide is taken up by plants and these plants are eaten by animals. Some of the carbon dioxide will have carbon-14 rather than the usual carbon-12. The animals that eat the plants will then have some of the carbon-14 in their bodies. The carbon-14 in the bodies of the animals will be in the same same ratio or proportion that it was present in the atmosphere. The sequence is cosmic radiation produces carbon -14, it is incorporated into carbon dioxide, this is used by plants, and the plants are then eaten by animals. This is how carbon-14 gets into animals and the important point is that the ratio of carbon-14 to carbon-12 in animals that are alive is the same as the ratio of carbon -14 to carbon -12 in the air.
This ratio begins to change after an animal dies. Carbon-14 is not a stable atom and changes back to the usual carbon-12 over time. This is called carbon-14 decay. After an animal dies it no longer eats any plants so there is no more carbon-14 going into the animal. There is an initial ratio of carbon-14 to carbon 12 which is equal to the ratio in the air at the time of death. Then the ratio changes as the carbon-14 decays into carbon-12 while no more carbon -14 in being consumed. We know how long it takes carbon-14 to decay. This is called the half-life. The half-life of carbon-14 is about 5,730 years. This means after 5,730 years half of the carbon-14 will have decayed into carbon-12. In the next 5,730 years or after 11,460 years, half of this half will decay into carbon-12. After these two half-lives, 11,460 years, only one fourth (one half of one half) of the carbon-14 will be present and three fourths will have decayed into carbon-12. This rate continues where every 5,700 years another half of what is left of the carbon-14 decays, or is changed into carbon-12.
Scientists are able to measure the amount of carbon-14 and the amount of carbon-12 in the remains of dead animals. By calculating the ratio of of carbon-14 and carbon-12 and knowing the half-life of carbon-14 they can calculate how long ago the animal died. This can never give an answer of millions of years because after millions of years there would be no detectable carbon-14. It is actually the opposite, if anything has carbon-14 it is not millions of years old. Like all of the methods to estimate ages, carbon dating is based on assumptions which make it difficult to be certain of any date. Has the ratio of carbon-14 to carbon-12 in the atmosphere always been constant? It is based on cosmic radiation and carbon dioxide production on the planet. The carbon dioxide emitted from volcanoes is depleted in carbon-14 so periods with high volcanic activity, as likely occurred during Noah’s flood, would change this ratio as well. If it has not been constant all the calculation would be wrong. In addition plants do not use the carbon dioxide that has carbon-14 the same as the carbon dioxide that has carbon-12. This discrimination for types of carbon dioxide varies with different types of plants. All of these variables affect the accuracy of the calculation, and usually give an answer that would be older than is real. In any event, carbon dating can only date for thousands of years, never for millions of years.