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 This page describes one mechanism by which antigravity matter can
create galaxy spiral arms. In this description it is assumed that the volume of
space affected by the antigravity matter vortex is spherical.
This
mechanism for creating drag spirals requires that there is not too much
winding in the galaxy disc. Winding is
where objects orbiting at a large radius take longer to complete an orbit
than objects orbiting at a small radius.
Where there is a lot of winding any radial or spiral structure will be
quickly shredded.
Winding is
reduced when the antigravity matter vortex has bottomed-out. That is, the density of antigravity matter
within the galaxy is low and fairly constant over a large radius.
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 Within the bottomed-out region both the gravitational acceleration
felt by a normal matter object and the circular orbital velocity of a normal matter
object increase in proportion to radius as explained here. Well away from the centre the gravitational
acceleration reduces according to the inverse square law.
The result
is that a group of stars in the bottomed-out region can orbit in almost fixed
formation independent of radius. If
one of the stars in the group loses kinetic energy it moves approximately
radially inwards in relation to its neighbours. Further out there is a lot more winding and
outer stars get left behind by inner stars.
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 Consider a group of stars orbiting
within such a bottomed-out region.
They pass though antigravity matter and experience AGM Drag. They lose energy and spiral inwards towards
the centre. The group’s antigravity
matter wake stretches out behind it in the direction of the relative flow of
the antigravity matter wind. In the
region of this wake the effect of the antigravity matter wind is reduced.
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 Now consider a second group of stars
which happen to be orbiting the galaxy in the wake of the first group.
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 The second group experiences less
drag and loses energy slower. The
first group moves inwards almost radially with respect to the second group
until the second group is no longer within the wake of the first group. The second group then feels more drag and
begins to move inward with the first group.
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 A third group of stars similarly
finds a stable position when it moves out of the wake of the first two groups
and further groups continue to add to the sequence. Eventually the groups build a spiral arm. The arm is aligned at a shallow angle to
the relative direction of the antigravity matter wind.
Small
fluctuations in the density of stars may exist along the length of the
arm. An area of reduced density causes
an increase in the drag on the stars just outside (downwind from) that
area. Those outer stars then lose
energy and fall inwards faster to fill the density gap. Similarly an area of increased density
causes a reduction in drag on the stars just outside (downwind from) that
area. Those stars move inwards more
slowly relative to those that are not shielded. Anti gravity
matter therefore provides a mechanism by which the spiral arm tends to retain
its linear structure and for example tends not to degrade into separate
groups of stars.
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 The stars generate molecular clouds
either during or at the end of their lives.
The clouds are less dense than stars and are affected more by the
antigravity matter wind. The clouds
are swept outwards along the trailing edge of the spiral arm.
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 However winding may not be
completely eliminated. The outer end
of the spiral arm may take longer to orbit the galaxy than the inner end and the
arm is stretched. Eventually the arm breaks.
The leading end of the outer section slows due to drag and begins to
fall inward.
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