Path: utzoo!mnetor!uunet!husc6!mit-eddie!apollo!nelson_p@apollo.uucp
From: nelson_p@apollo.uucp
Newsgroups: sci.electronics
Subject: electronic time capsule
Message-ID: <3a623999.44e6@apollo.uucp>
Date: 19 Feb 88 19:27:00 GMT
Sender: user@apollo.uucp
Lines: 19
To: sci.electronics@news



 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