Asri-unix.869
net.space
utcsrgv!utzoo!decvax!ucbvax!ARPAVAX:C70:sri-unix!Hans
Mon Mar  1 12:31:10 1982
Red vs blue spaceships
Fooey, there was a square root dropped in the beam angle calculations
of my last note.  The aberration in beam angle for a source emitting
a narrow beam in the direction of travel should have read:
                                              1 + v
Aparent beam angle = Source beam angle * SQRT(-----)
                                              1 - v
with v being recession velocity as fraction of c.

	This means that photon starships moving with the typical
quasar velocity of .82 c are only about 100 times as likely to
be seen accelerating away from us as decelerating towards us.
This is still in plausible agreement with observation since most
of the 200 quasars that have been identified were found by looking
for large redshift.   And if the data should rule out the narrow
blue beam possibility in future, we can always fall back on the
hypothesis that there are better ways to slow down than using the
big engines used for acceleration.

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