What is half life decay?
Half life decay is a phenomenon mostly found in radioactive elements which causes the substance to lose its original mass by one-half when a particular time called half-life has already passed.
Imagine 1 kg of Plutonium-244. Plutonium 244 is a radioactive isotope of Plutonium and has a half-life of 80.8 million years. Again, half-life is the amount of time required to reduce the mass of a particular substance by half. Thus, after 80.8 million years, the mass of our original substance would reduce to 0.5 kg. This is due to the fact that the particles of the substance dissipate or decay into energy such as gamma rays.