More Geiger counter stuff

I keep promising to write up things about my life on here, like my astonishingly fabulous weekend with ergotia, lilithmagna, and calar, but the thing that usually inspires me to write is some geek nonsense, so here we go again.

Everyone knows that radioactive decay is truly random: whether or not a given nucleus will decay in the next second is entirely down to chance. If it doesn't decay this second, the chances that it'll do so in the next are exactly the same. If it survives another million years, it still has the same chance of decaying in the second following that; it doesn't "age". For the nucleus, every second is a game of Russian Roulette, and there are always the same number of bullets in the barrel. That's why you can't measure the "life" of a radioactive source - instead, we measure the "half-life", which is the time it takes before the chances it'll have decayed are 1/2 - or to put it another way, the time before half the nuclei in a given sample have decayed.

So it's an appealing source of random numbers - stick a Geiger counter next to a radioactive source, and the "clicks" are randomly distributed. If the source is large enough and has a long enough half life, we can ignore its slow decay, and treat each "click" as an independent event - the probability of a click in the next millisecond is the same no matter what the history is.

Only it isn't. ( Read more... )