The dark side of cosmology

THERE should come a time in every parent's life when his child sees her first picture of a galaxy. The child, demanding to know all, will be told that those tiny lights spiralling around in it are suns, each separated from its kin by distances too great to fit inside the human mind. She will probably respond, with the annoying logic that is the hallmark of new people, “Well, why don't they all fly apart?” To which the wise parent will answer, “Gravity, my little one.”