To measure the passage of long periods of time, scientists take advantage of a regularity in certain unstable atoms.
In radioactive atoms the nucleus will spontaneously change into another type of nucleus.
Scientists can use the half-life of Carbon-14 to determine the approximate age of organic objects less than 40,000 years old.
By determining how much of the carbon-14 has transmutated, scientist can calculate and estimate the age of a substance. Isotopes with longer half-lives such as Uranium-238 can be used to date even older objects.
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.
Not only does it decay by giving off energy and matter, but it also decays at a rate that is characteristic to itself.Half-lives for various radioisotopes can range from a few microseconds to billions of years.See the table below for a list of radioisotopes and each of unique their half-lives. After 86 minutes, half of the atoms in the sample would have decayed into another element, Lanthanum-139.Scientists use C-14 in a process called carbon dating.Carbon dating is when scientists try to measure the age of very old substances.Depending on the isotope, its Half Life may range from a few fractions of a second to several billion years. The Half Life of Uranium-238 is 4,500,000,000 years.