Sorry to bump such an old thread! I'm browsing my old posts and never realized you responded. Just wanted to say thanks for the suggestion. That was never something I considered but in retrospect it actually makes the most sense.
Remember how they jumped over the wall into Buckaroo's compound? Of course that would indicate that our gravity is lighter to them, but still, it doesn't discount that our gravity may behave different than their own.
That line though is still hilarious. It's delivered in such a deadpan style.
...For every man who has ever lived, in this universe, there shines a star. -Arthur C. Clarke