Enter value and click on calculate. Result will be displayed. The Half Life Time of a quantity whose value decreases with time is the interval required for the quantity to decay to half of its initial value. The term Half Life Time was coined in The Half Life Time is the amount of time it takes for half of the atoms in a sample to decay. Half Life is a characteristic of each radioactive isotope.
Uranium—lead dating , abbreviated U—Pb dating , is one of the oldest  and most refined of the radiometric dating schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over 4. The method is usually applied to zircon. This mineral incorporates uranium and thorium atoms into its crystal structure , but strongly rejects lead when forming. As a result, newly-formed zircon deposits will contain no lead, meaning that any lead found in the mineral is radiogenic. Since the exact rate at which uranium decays into lead is known, the current ratio of lead to uranium in a sample of the mineral can be used to reliably determine its age. The method relies on two separate decay chains , the uranium series from U to Pb, with a half-life of 4.
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.
Unstable nuclei decay. However, some nuclides decay faster than others. For example, radium and polonium, discovered by Marie and Pierre Curie, decay faster than uranium.