Flying swiftly on bat-wings
How's that work in space?
In game, we can try to explain it with some technobabble. Perhaps anti-gravity devices exist, but only work at slow speeds? Of course, this doesn't work for Mutalisks. They actually flap their wings to stay airborne and move around. The great blog Science of Starcraft tries to explain the wings as solar sails, but in the end the math doesn't work out. They conclude that the explanation for flying Mutalisks is: magic. I don't know about that... surely there must be a way they can fly, maybe it has to do with neutrinos?