Asri-unix.888
net.space
utcsrgv!utzoo!decvax!ucbvax!sri-unix!HPM@CMU-20C@Berkeley@CCA-UNIX
Wed Mar  3 18:30:54 1982
Quasar starships
Re:

1) Short term brightness changes in quasars

   Paragraph from "The Evolution of Quasars" by Maarten Schmidt
   and Francis Bello   May 1971
     "Unlike the light output of normal galaxies, the light output
      of some quasars has been observed to change significantly
      in a matter of days.  The only explanation is that some variable
      component, if not the entire quasar, may be much larger than
      the solar system."  - One point for the starship hypothesis.

2) Long term brightness changes

    Since short term changes are irregular, there must be some.  In
    any case, the 20 years since the first quasar discovery is a short
    interval in a 1000 year trip.  Anybody have data on this?

3) Increases in red shift with time

     I chose .001 g as a plausible acceleration because it allows a
     continuously accelerated 1000 light year trip in a total conversion
     photon rocket with a mass ratio under 10.  By comparison, at .01 g
     the mass ratio is nearly 200.  Over a 10 year period .001 g gives
     a velocity change of .01 c, from .82c to .83c at typical quasar
     velocity, a change in redshift from 2.18 to 2.28.  The quasar
     articles I've seen give redshifts to two decimal places, so a
     change of this magnitude should be detectable.  Any lower bounds
     on redshift change known?  A less than .01 change in ten years
     would imply an acceleration of less than 10e-5 g.
     Low values could be explained as being reasonable for something
     less than total conversion. (The spectral lines (H, C, Mg) of
     quasars show that there is a mix of stuff there).  A detected
     increase in redshift would be very strong evidence for a rocket,
     but lack of such would be a strong negative indication.  Any data?

4) Density correlation with the galactic disk

     The stellar neighborhood is pretty isotropic in a thousand lightyear
     sphere, and farther away they would be harder to see.  Also, most quasar
     searches have been made out of the galactic plane, because the
     in-plane sky is so cluttered.  A quasar set against a background
     of a galactic dust cloud would, of course, be wonderful evidence
     of them being nearby.    But only 200 have been found so far, so the
     evidence is not yet in.  The Feb 82  Osmer Sci. Am. article statement
     that there seems to be no correlation between redshift and brightness
     is positive evidence.
     Perhaps related, from the same article: "The spectra of quasars are
     quite unlike the spectra of all other astronomical objects ...
     The strongest feature is the Lyman-alpha line of atomic hydrogen ...
     ... in many instances the lines are wide, an indication that
     some of the gas surrounding the quasar is moving at velocities as
     high as [ 0.1 c ].  The physical conditions deduced from the various
     lines show that the gas is hotter than the gas in normal nebulas ..."

5) Power output of a quasar-bright starship (other message)

	Yes, the huge energy output is entirely predicated on them
     being at the edge of the visible universe.  Their power output
     drops by inverse square law.  If they are at 10e10 light years,
     their output (if isotropic) is that of 10e13 stars.  
     	If they are only 1000 lightyears distant and isotropic the
     output is one tenth that of a star.
     	If the power output is concentrated into a one degree of
     divergence beam, one millionth of a stellar output suffices.
     This is 10e27 ergs per second.
        If the power for this last case is provided by total
     conversion, it means conversion of 1000 kg, or 1 tonne, of
     fuel per second -  Certainly awesome by our standards, but
     much smaller than astronomical in scale, and probably not
     absurd for a mature starship technology.
        Assuming, as before, a 1000 light year trip and 10 mass ratio,
     thus .001 g  acceleration we  can calculate that the mass of a
     typical quasarship to be 10^11 tonnes, 100 billion tonnes.
     (By comparison, the earth masses 10^22 tonnes.)  If the ship
     has the density of water, it might be contained in a sphere
     10 kilometers in diameter.  (Sounds just right to me!)
     	Because of the small fraction of such ships which would
     have their narrow beams aimed at us, the density of visible
     quasars would imply that there are maybe 100 billion of these
     cuties within a few thousand light years.  Could be big
     trouble later if they're not very friendly.
-------

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