Radioactive Decay

Process affecting all radioactive elements in which they gradually and steadily lose atoms. It is expressed as half-life, which is the time it takes for half of an element’s atoms to decay. Half-life may be very short (fractions of a second) or extremely long (several billion years). This property is used to date objects (carbon-14 dating of objects a few hundred to 50,000 year old) and calculate the age of the Earth (uranium-238) or the universe (thorium-232).