Well, much as I hate defending this show, I'll give them this much, at least--they couldn't dial back to earth.

Reaching another galaxy (and they're many galaxies away) requires far more power than is available on your standard stargate. It requires a ZPM (an Ancient uber-battery) or two. Or a whole planet devoted to powering the gate, as in the pilot of this execrable series.

So they can't just dial home. The ship was running on fumes when they arrived. Or they couldn't before the ship charged up its power cells. They'd damn well better TRY in the next episode, though.