Radiometric dating

Radiometric dating is a special way scientists use to figure out how old things are, like rocks or even ancient artifacts. It works by looking at tiny bits of certain materials that give off a steady, predictable amount of energy over time. By measuring how much of the original material is left and how much has changed, scientists can calculate the age of the object.

This method was first used by scientists Ernest Rutherford and Bertram Boltwood in the early 1900s. Since then, it has become one of the most important tools for learning about the history of our planet and its life. It helps us know how old Earth is, how long ago dinosaurs lived, and even when human-made objects were created.

There are several kinds of radiometric dating, like radiocarbon dating for things up to about 50,000 years old, and uranium-lead dating for much older objects. Together with other geological methods, these techniques help build a timeline of Earth's history and the changes in life over millions of years.

Fundamentals

All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus. Elements can exist in different forms called isotopes, which differ in the number of neutrons in the nucleus. Some isotopes are unstable and can change over time through a process called radioactive decay, turning into a different isotope. This change happens in predictable ways, such as emitting small particles.

The rate at which these changes happen is constant and is known as the half-life. This rate does not change based on outside conditions like temperature or pressure. Because of this, scientists can use the amount of original isotope and the amount of its decay product to estimate how long ago the material formed. This method, called radiometric dating, was pioneered by scientists like Ernest Rutherford and Bertram Boltwood in the early 1900s.

Main article: Closure temperature

Modern dating methods

Radiometric dating has been used since 1905 when it was invented by Ernest Rutherford to figure out the age of the Earth. Over the years, these methods have gotten much better and can now work with very tiny samples. Scientists use special machines called mass spectrometers to measure the tiny bits of radioactive materials in rocks and other objects.

One common way to date very old rocks is called uranium-lead dating. It uses two types of uranium that change over time into lead. By measuring how much lead is left, scientists can tell how old a rock is. Another method, radiocarbon dating, works well for things that were once alive, like bones or wood. It measures a special kind of carbon that disappears over time after an organism dies. These methods help us learn about the history of our planet and even ancient artifacts.

Main article: Uranium–lead dating

Main article: Samarium–neodymium dating

Main article: Potassium–argon dating

Main article: Rubidium–strontium dating

Main article: Uranium–thorium dating

Main article: Radiocarbon dating

Main article: fission track dating

Main article: Luminescence dating

Dating with decay products of short-lived extinct radionuclides

Absolute radiometric dating needs a certain amount of the original material to be present in a rock sample. For very old rocks, such as those from the beginning of the Solar System, this can be difficult because the original materials may have decayed away over time.

Scientists can study the decay products of very short-lived materials that are no longer present in rocks. These materials, such as ²⁶Al, ⁶⁰Fe, ⁵³Mn, and ¹²⁹I, were created when stars exploded long ago. By measuring how much of these decay products are left in very old materials like meteorites using a special tool called a mass spectrometer, scientists can figure out the relative ages of events from the early solar system. This method helps give a more detailed timeline than using longer-lasting materials.