Not a physicist or astronomer, but here's one answer: my understanding is that the supermassive black hole at the center of the Milky Way imposes order on the rest of the bodies of the galaxy, in the same way that our sun imposes order on the planets and other bodies in the solar system. Absent that order, we'd likely have more frequent encounters with other stars, possibly disturbing planetary orbits enough that it could end life on this planet... perhaps by pushing Earth out of the Goldilocks zone, perhaps by inducing the moon to collide with us, or drive a shower of asteroids in at us...
Save that for a fun bedtime story on a stormy night.
Last edited by Dude; 03/13/15 11:34 AM.
