Peter bayley writes "Tell me I'm crazy or tell me someone has already done it — but wouldn't a satellite equipped with a laser be a great way to warn people of tsunamis? I was pondering how to warn people in remote coastal areas once evidence of a seismic incident has been received by the monitoring stations that have now been set up following the large Boxing Day tsunami. The idea is to illuminate the areas that are likely to be at risk with a bright (but not dangerous) light. People would be told to head to higher ground if such a light appears in the sky. Put the satellite in a geosynchronous orbit. Make it tunable so that different colors can convey different meanings. You would be able to warn anyone, anywhere they can see the sky. The laser could be directed to illuminate only those areas at risk, skipping unnecessary areas to save power. Power could be varied so that it is visible day and night and through cloud (raise the power where the satellite detects cloud cover). I emailed some people at NOAA about it but they said it would stand on too many toes by circumventing local emergency service organizations in the various countries. I replied that countries could easily opt out, in which case the laser would be turned off for those countries — but received no further reply. Anyway, I thought the massed minds of Slashdot would relish the chance to demolish my idea."