Where's North?

Walking back the through the village to our house Grace, 4, suddenly asks 'Where's North, Daddy?' I'm usually good at unravelling concepts for children but this one is hard. I wave my arm vaguely across the fields to our right where rain looks to be pressing in to ruin our day. 'Over there, where those clouds are. Do you see?' 'Can I go there?' 'Not really darling. It's a direction.' Hopeless. 'You remember how I told you that we live on a giant ball. Well when we walk up that ball we're going North.' Still no good.