Radiometric Dating: Methods, Uses & the Significance of Half-Life
Looks like you are using an old version of Internet Explorer - Please update your browser. If you already have an account, Sign in. Once you understand radimoetric basic science, however, you can see how wrong assumptions lead to incorrect dates. Problems with the Assumptions. Making Sense of the Patterns. This three-part series will radiometroc you properly understand radiometric dating, the assumptions that lead to inaccurate dates, and the clues about what really happened in the past.
Most people think that radioactive dating has proven the earth is billions of years old. After all, textbooks, wyat, and museums glibly present ages of millions of years as fact. Yet few people know how radiometric dating works or bother to ask what assumptions drive the conclusions. Each chemical element, such as carbon and oxygen, consists of atoms.
Each atom is thought to be made up of three basic parts. The nucleus contains protons tiny particles each with a single positive electric charge and neutrons particles without any electric charge. Orbiting around the nucleus are electrons tiny particles each with whqt single negative electric charge. The atoms of each element may vary slightly in the numbers of neutrons within their nuclei. These variations are called isotopes of that element. While the number of neutrons varies, every atom of any element always has the same number of protons and electrons.
So, for us, every carbon atom contains six protons and six electrons, but the number of neutrons in each nucleus can be six, seven, or even eight. Therefore, carbon has three isotopes variationsamwf dating site are specified carbon, carbon, and carbon Figure 1. Some isotopes are radioactive; that is, they wamba dating unstable because their nuclei are too large.
To achieve stability, the atom must make adjustments, particularly in its nucleus. In some cases, the isotopes eject particles, primarily neutrons and protons. These are the moving particles measured by Geiger counters and the like. The end result is a stable atom, but of a different chemical element not carbon because the atom now has a different number of protons and electrons.
This process of changing one element designated as the parent isotope into another element referred to as the daughter isotope is called radioactive decay. The parent isotopes that decay are called radioisotopes. The daughter atoms are not lesser in quality than the parent atoms from which they were produced. Both are complete atoms in every sense of the word.
Geologists regularly use five parent isotopes to date rocks: These parent radioisotopes change into daughter lead, lead, argon, strontium, and neodymium isotopes, respectively. Thus what is the radiometric dating refer to uranium-lead two versionspotassium-argon, rubidium-strontium, or samarium-neodymium dates for rocks. Note that the carbon or radiocarbon method is not used to date rocks most rocks do not contain carbon.
They must find rocks that have the isotopes listed above, even if these isotopes are present only in minute amounts. Most often, this is a rock body, or unit, that has formed from the cooling of molten rock material called magma. The next step is to measure the amount of the parent and daughter isotopes in a sample of the rock unit. Specially equipped laboratories can do this with accuracy and precision. So, in general, few people quarrel with the resulting chemical analyses.
It is the interpretation of these chemical analyses that raises potential problems. In an hourglass, grains of fine sand fall at a steady rate from the sating bowl to the bottom. After one hour, all the sand has fallen into the bottom bowl. So, after only half an hour, half the sand should be in the top bowl, and the other half should be in the bottom bowl. Suppose that a person did not observe when the hourglass was turned over.
What is the radiometric dating walks into the room when half the sand is in the top bowl, and half the sand is in the bottom bowl. By way of analogy, the sand grains in the top bowl represent atoms of the parent radioisotope uranium, potassium, etc. The radjometric sand represents radioactive decay, and the sand at the bottom represents the daughter isotope lead, argon, etc.
When a geologist tests a rock sample, he assumes all the daughter atoms were produced by the decay of the parent since the rock formed. So if he knows the rate at which the parent decays, he can calculate how long it took for the daughter measured in the rock today to form. But what if the assumptions are wrong? For example, what if radioactive material was added what is the radiometric dating the top bowl or if the decay rate has changed?
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Back to Basics by Dr. Snelling on June 17, ; last featured February 19, Radiometric Dating PART 1: Back to Basics PART 2: Problems with the Assumptions PART 3: Making Sense of the Patterns This three-part series will help you properly understand radiometric dating, the assumptions that lead to inaccurate dates, and the clues about what really happened in the past. Prev ious Article Quieter Than a Speeding Bullet.
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