Peter Davidson: In the changing of the light we glimpse the true meaning of 'north'

The more you think about the word "north" the more that it seems a term which will always be relative. There are always other norths beyond the north you inhabit, until eventually you come to the unnegotiable north of the icecaps and the pole. Proverbially "north" is an unstable idea, an idea that moves away from you, eludes you. "North" is so often "north of here", receding and shifting and passing out of reach. North is so often north of where you stand. Of all geographical terms, it is the most personal, the most emotional, the most elusive. And the one which evokes perhaps the most powerful feelings.

There are many imaginary lines on the maps which have been seen over the centuries as the frontiers of the north – or at least of one version of north, one attempt to fix an elusive idea to a firm geography. By the time he turned 20, the poet WH Auden had already decided that the north began where English brick gave way to stone, where hedges gave way to dry-stone walls. There are other frontiers, Latin languages giving way to Germanic ones. Butter rather than olive oil, fish as a staple rather than meat, wheat giving way to rye. The weather map is often a map of north and south, and snowy winters are seen to define the north.

The ancient boundaries of the Roman Empire still surface from time to time in the European consciousness as a frontier of the north. The lonely five-peaked mountain which dominates the skyline of Aberdeenshire, Benneachie also known as Mons Graupius, is the farthest north which the Empire's armies reached before the Picts and the shadowy tangle of the northern forests were too many for them.

We could go on multiplying relative frontiers of the north, but I would like to advance one unmistakable marker of northness on which we can probably all agree, and that is the fall of the light and the presence and absence of light in the round of the year. The long midsummer evenings from which I began are uniquely of the north, as are those midwinter days which you get even in London when the sky never seems to have been switched on properly.

Taken from a talk – 'The Idea of the North' – to be given at 6pm this evening by Prof Peter Davidson of Aberdeen University at Gresham College, London EC1