# Radioactive dating the earth

Radiometric dating involves dating rocks or other objects by measuring the extent to which different radioactive isotopes or nuclei have decayed. Although the time at which any individual atom will decay cannot be forecast, the time in which any given percentage of a sample will decay can be calculated to varying degrees of accuracy. The time that it takes for half of a sample to decay is known as the half life of the isotope. Some isotopes have half lives longer than the present age of the universe , but they are still subject to the same laws of quantum physics and will eventually decay, even if doing so at a time when all remaining atoms in the universe are separated by astronomical distances. Various elements are used for dating different time periods; ones with relatively short half-lives like carbon or 14 C are useful for dating once-living objects since they include atmospheric carbon from when they were alive from about ten to fifty thousand years old.

## How is Earth's Age Calculated?

## The Age of the Earth - Radiocarbom Dating as a Current Scientific Clock: Jonathan Ring

Radioactive dating uses the decay rates of radioactive substances to measure absolute ages of rocks, minerals and carbon-based substances, according to How Stuff Works. Scientists know how quickly radioactive isotopes decay into other elements over thousands, millions and even billions of years. Scientists calculate ages by measuring how much of the isotope remains in the substance. The key to an age of a substance is the decay-product ratio. The ratio of the original isotope and its decay product determines how many half-lives have occurred since the sample formed.

### Radioactive Dating Age Of Fossils

When asked for your age, it's likely you won't slip with the exception of a recent birthday mistake. But for the sprawling sphere we call home, age is a much trickier matter. Before so-called radiometric dating, Earth's age was anybody's guess. Our planet was pegged at a youthful few thousand years old by Bible readers by counting all the "begats" since Adam as late as the end of the 19th century, with physicist Lord Kelvin providing another nascent estimate of million years. Kelvin defended this calculation throughout his life, even disputing Darwin's explanations of evolution as impossible in that time period.

The discovery of the radioactive properties of uranium in by Henri Becquerel subsequently revolutionized the way scientists measured the age of artifacts and supported the theory that Earth was considerably older than what some scientists believed. However, one of the most widely used and accepted method is radioactive dating. All radioactive dating is based on the fact that a radioactive substance, through its characteristic disintegration, eventually transmutes into a stable nuclide. When the rate of decay of a radioactive substance is known, the age of a specimen can be determined from the relative proportions of the remaining radioactive material and the product of its decay. In , the American chemist Bertram Boltwood demonstrated that he could determine the age of a rock containing uranium and thereby proved to the scientific community that radioactive dating was a reliable method.