> If you meant, "Why can't we precisely predict the motions of a vast rock floating in space years into the future" then I don't know what to tell you. We're no

> If you meant, "Why can't we precisely predict the motions of a vast rock floating in space years into the future" then I don't know what to tell you. We're not God? IMO this feels like the more interesting one to explore: are leap seconds wholly from things that are within measurement error in existing rotation, or is the Earth's rotational rate actually changing? If we had leap minutes as the smallest increment, could we predict them out centuries in advance? etc