RE: starship-design: WHERE ARE THEY?

[Steve VanDevender <stevev@efn.org>]

L. Parker writes:
 > > If this is true then gamma-ray burst events are even more common,
 > > but we can see only those whose beams point at us.  However, it
 > > is then unlikely that gamma-ray bursts can sterilize galaxies.
 > 
 > No, it doesn't change the end result at all as far as the equation is
 > concerned. It just means that there are more of them to make up the
 > difference. Statistically, the end result is the same. We seem to have just
 > been extremely lucky in that none have been pointed our way in somewhat more
 > than the allotted amount of time.

Actually, plenty are pointed our way -- otherwise we wouldn't
keep detecting them so frequently.

Statistically, though, the result is not the same.  On a
universe-wide scale, there are plenty of gamma-ray bursts for
everyone to see.  If GRBs are isotropic, then, yes, potentially
each burst we see has sterilized a large portion of its host
galaxy.  But if GRBs aren't isotropic, then individual GRBs
aren't sterilizing huge parts of the galaxies they occur in, and
at a galaxy-wide scale there aren't enough close GRBs to clear
galaxies of life.