Steve Allen wrote: > I remember my mom's wind-up travel clock glowing brightly. 50 years > later there is nothing. I brought it into the lab just to check that > it is still radioactive (wouldn't want to have lost that radium > somewhere). It's the zinc sulfide crystals, the radiation damages > them and they stop producing light.
Steve, another example of that happening, is in this video by Fran Blanche, where she tests the clock face of an old radio-clock, showing that it no longer "glows in the dark" but the radio-active source is never the less still there ! I have set the start to be at the 15 minute mark, to save watching the whole mailbag! https://www.youtube.com/watch?v=0J3cu67SBZY#t=15m Regards, Geoff (NZ) _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
