Is there something special about the halfway point? Does the decay happen at a steady pace or exponentially?
In: 910
It’s more like a speed than a time. The time it takes a chunk of stuff to decay will depend on how much of it you have, so you can’t just put some “decay time” on an element that works in every case.
Instead, half life tells us how fast it will decay, and we can apply that to any amount that we might have.
Now, the reason we use half life and not like atoms-per-second or something is because radioactive decay is exponential, not linear. The more of it you have, the more atoms will decay per given length of time. The thing that stays constant, though, is how long it takes for *half of whatever you have* to decay. Got a billion atoms? In one “half life” of time you’ll have 500 million. Then 250 million. Etc. You can see how the speed decreases over time, and that’s why a linear unit wouldn’t work.
(note that there’s nothing special about using half. We could just as well define third lives or ninth lives, which would tell us how long it takes for a third or ninth of whatever we have to decay. But this is just unnecessarily convoluted, so we use halves to keep things as simple as we can)
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