awesome demonstration of a massive diffusion cloud chamber - with normal background radiation vs. americium 241 vs. the epic RADON 220 gas! just wow! ps: yeah, i know i accidentally said "Radium 220" instead of "Radon 220" once - and that i said "half time" instead of "half life" a couple of times. sorry about that, i was just drained after that awesome day at the museum and thus, unable to concentrate properly.