How does an symphony orchestra conductor communicate with the orchestra musicians if they don't look at him?

I've noticed from watching videos of symphony orchestras that the musicians rarely look at the conductor while they are playing, or so it seems to me. If they are resting they'll look for cues to come in but not while playing, except sometimes for players who have a solo part (i.e., winds) or something like that. So how do they absorb what the conductor is doing?