If you had an anti-gravity propulsion device, it would always have to be sort of in front of you somehow. But then you have to be constantly moving this thing for you to fall towards it. So I don't fully know how you would make an anti- gravity element pull you across the galaxy,. much less to the piggyly wiggly. Alex Kawakowski: How realistic is the idea of a gravity gun? He says we're a long way away from such a gun.