From: henry@spsystems.net   
      
   In article ,   
   Keith F. Lynch  wrote:   
   >> In the long run, when these things get *common*, then it's going   
   >> to be necessary to have space traffic control, and police/military   
   >> forces are going to need the ability to shoot down such vehicles...   
   >   
   >What about the really long term, when we have relativistic starships?   
   >By the time it's noticed that a ship is approaching earth at 90% the   
   >speed of light, it's far too late to do anything about it...   
      
   I don't think that's necessarily true.  It does mean having good detection   
   systems a long way out, because some advance warning is needed and that   
   requires a lot of distance at such speeds.  But such a starship is itself   
   quite vulnerable in some ways.  Its approach path is very predictable, and   
   if you can use something like a relativistic mass driver to throw a few   
   grams of buckshot into its path as it comes in past Jupiter, what hits   
   Earth will be a very small portion of the expanding plasma cloud.  Still a   
   matter of some concern, but much less devastating.   
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   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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