Ladies and Gentlemen, the greatness of Roger Ebert:
From where [Dr. Manhattan] stands, he might as well be regarding a termite. Why does he even bother to make love with Laurie Jupiter? Not for his own pleasure, I'm convinced. And not to father a Little Manhattan, either, because as I understand his body he would ejaculate only energy. Could be fun for Laurie, but no precautions needed, except not to be grounded at the time.