It has never been stated that other worlds or species or
civilizations don't have the technology to use gravity, magnetic or other
forces to move objects. It was used in "Sky Full of Stars" when the
Minbari cruiser pulled in Sinclair's ship. *We* don't have that tech
yet, and must work around it, but a few others do. As with the other
note I left on another topic, I don't see the problem here. This seems
perfectly within the realm of probability for any reasonably advanced
species; it's just that we haven't reached that point yet.

jms