🚀 go-pugleaf

 In reference to my idea of an electronic time capsule  (a solar-
 powered device which remains mostly dormant for decades or
 centuries, ultimately 'waking up' and calling attention to itself
 via a radio signal) I got the following suggestion on how to
 time out all those years before awakening:

> try radioactive decay for timing.  Inherently stable, easy to count,
> small, low power.

  This is potentially a very good idea, having many advantages 
  over my other proposals.  Questions:  How can I sense the 
  radioactivity?  G-M tubes are not particularly long-lived devices;
  depending on how they're quenched and how much radiation they're
  exposed to, they may be good for a few decades at best.  Are there
  reliable solid-state detectors?   Also what materials would have a 
  sufficiently short half-life to be suitable?  

                                      --Peter Nelson