>>502
The vacuum of space is just that, a vacuum; there's nothing actually there. You can't move or suck in or out nothingness. You might be thinking of those diagrams of gravity wells which show space being bent out of shape, but changing that would require creating and destroying planet or star sized objects for each pulse. This is not only incredibly impractical, but the effect would barely be measurable outside our solar system, let alone galaxies away.

Radio waves, on the other hand, travel at the speed of light and aren't diminished by long distances. This is good because if there is any life out there, it's going to be many many light years away.