# Why is radioactive decay measured in half-life instead of the full time?

Aug 10, 2014

Because the full time is infinitely long.

#### Explanation:

Because the full time is infinitely long.

Say you had to cover a distance of 5 m.

In the first second, you would cover half the distance.

In the second second, you would cover half the remaining distance.

In the third second, you would cover half the remaining distance , and so on.

You would never reach your goal, because there is always a small distance yet to cover.

It's the same with nuclear half-lives.

In the first half-life, half of the atoms disappear, and half of them remain.

In the second half-life, half of these atoms disappear. One-fourth of the original atoms remain.

In the third half-life, half of those remaining atoms disappear. One-eighth of the original atoms remain, etc.

The atoms will never completely disappear. There are always some remaining that have yet to decay.