Scientists look at half-life decay rates of radioactive isotopes to estimate when a particular atom might decay.
A useful application of half-lives is radioactive dating.
Often students get bogged down in the fact that they don't "understand" how and why radioactive elements decay and miss the whole point of this exercise.
If they can begin to comprehend that it is random and spontaneous, they end up feeling less nervous about the whole thing.
We can get absolute ages only if we have rocks from that surface.
Radioactivity and radioactive decay are spontaneous processes.
The half-life is the amount of time it takes for one half of the initial amount of the parent, radioactive isotope, to decay to the daughter isotope.
Thus, if we start out with 1 gram of the parent isotope, after the passage of 1 half-life there will be 0.5 gram of the parent isotope left.
We have rocks from the Moon (brought back), meteorites, and rocks that we know came from Mars.
We can then use radioactive age dating in order to date the ages of the surfaces (when the rocks first formed, i.e. We also have meteorites from asteroids and can date them, too.