Airport explosive detection system

[Kathi Elliott <KELLIOTT@WPO.IUPUI.EDU>]

This thread reminded me of an interesting (and somewhat embarrassing)
event that happened on my way to the HPS meeting a few years ago in
Atlanta.  As my carry-on bag passed through the x-ray machine, the
person had a perplexed look and mumbled something about some darkening
on the screen.  A security guard came over and proceeded to inspect my
bag.  When they reached down and pulled out my old Westclox clock, and
noted that area of the bag as the location of the darkening, I explained
that the clock did have a radium dial.  It was on the edge of my bag
with the dial facing outward, but I was a bit surprised that it would
cause such darkening.  

P.S. In case anyone was wondering, those Westclox bells beat any buzzer
or telephone to wake up to.