Re: low profile

From: N.BOSTROM@lse.ac.uk
Date: Thu Oct 17 1996 - 09:55:47 MDT


          [appologies if this occurs twice]
          
          Robin Hanson wrote:
>could someone nova our star, or galactic centre?
          
          Forrest Bishop: wrote:
>Yes [then a story about inducing a fusion reaction in the
          outer layers of the sun]
          
          Does not sound plausible to me. First, if you would
          literally nova our "star" you would have to increase its
          mass by 40% -quite a heavy initiator! Even so, you would
          presumably have to wait millions of years before the sun had
          burned up its hydrogen fuel (and then helium etc) and begun
          to contract.
          
          If you wanted to induce an explosion by sending a bomb to
          the precritical region surounding the core, I don't think
          this would work either. The sun shines by hydrogen burning;
          there are enormous fusion bombs detonating in the sun every
          second. The balance between Coloumb forces and average
          kinetic energy must be quite robust, or stars would blow up
          at any time in the middle of their evolution.
          
          As for the galactic centre, it is more difficult to tell, I
          believe. I would think that a chain reaction would
          presuppose a high denisty of white dwarfs or equivalent.
          
          Moreover, a supernova explodes at only about 15000 km/sec,
          which an advanced civilisation could perhaps be possible to
          run away from. A lot of the energy is also released in the
          form of neutrinos, which travel at approximately the speed
          of light; but then again there is a very small cross section
          for neutrino reactions, so one could stand a very heavy
          neutrino shower without getting hurt.
          
          In general, the effect of any cosmic blast drops off as the
          inverse cube of the distance. Since cosmic distances are
          typically very large, such indiscriminate blasts would seem
          to be ineffective as means of warfare. Even a supernova
          explosion, which is about as violent as anything (short of
          big bang, or vacum decay or a big chain reaction of
          supernovae where such is possible) would not hurt us
          significantly if it were a few light years away, and an
          armoured civilisation could survive much closer.
          
          An "electomagnetic pulse of unspeakable amplitude" (Forrest
          Bishop) would also seem like science fiction proper.
          
          It is important that we use realistic assumptions about the
          conditions of cosmic warfare in our simulations. Since there
          are still many unsolved problems in fundamental physics, I
          suggest we set up several simulations with different
          parameters for weapon technology. There are several relevant
          variables here, such as projectile speed, production cost,
          identifiability of aggressor, technology level required for
          its manufacture, discrimination capabilities ("hurt only the
          bad guys"), etc. Maybe the time is ripe to begin to try to
          really work this out.
          
          Nicholas Bostrom n.bostrom@lse.ac.uk
          



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