Alan, VK2ZAY, has a really nice blog with all sorts of interesting experiments. Today's fun installment was a radiation detector that's just about as simple as can be imagined, ao aimple and inexpensive that I am pondering the possibility of using a similar circuit as part of a sensor for a balloon launch. Very cool:
It also made me realize that I didn't understand how a common smoke detector (which I know includes Americium, but little else) actually worked. Wikipedia of course comes to the rescue, and tells me the basic idea.