We used to frequent a restaurant in Kingussie. It was in the High Street and in the olden days you could park in front of the council offices across the road. We often went there in autumn and emerging from the car, having just pulled off the A9, the cold Highland air and smell of birch wood smoke sharpened the appetite.
All the seasons have a distinct smell. At the moment we have the damp fungal odours of fallen leaves decaying to mush while the last scents of summer have blown away. I find myself looking forward to the first frosts clearing the air completely, leaving it smelling of nothing but the occasional garden bonfire and, here in Edinburgh, the breweries. That yeasty smell still reminds me of returning for autumn term and meeting old friends in warm pubs.
These olfactory signs of the earth’s journey around the sun are inseparable from the pineal ones of changing day length. After all, it is the change in day length and declination of the sun that underlies everything else. A graph plotting day length throughout the year has the form of a sine wave with a peak in summer and a trough in winter. The implication of this type of curve is its effect on our perception of the rate of change. There is little change at the peaks and troughs but rapid change during the upwards and downwards slopes. The word solstice means ‘the sun stops’ and from late May to the end of July, around the peak of the sine wave, there is little perceptible change in the times of sunrise and sunset. The day lengthens slightly for a month then shortens slightly for a month, but it is always daylight when we wake up and always light at bedtime. It is this effect that makes it seem like the sun has paused at its zenith for a couple of months.
In the tropics, between Cancer and Capricorn, where day and night are roughly equal all year round, the sun sinks suddenly and vertically below the horizon and night rapidly follows day with little twilight. Living in the ‘far north’ as we do, the situation is more complicated than the simple time that elapses between sunrise and sunset. In Edinburgh, a graph of light levels rather than simply the time between sunrise and sunset shows that around midnight in summer, when the sun dips briefly below the horizon, there is still enough light bending round the earth to create a continuous ‘gloaming’ between sunset and sunrise. At the summer solstice the peak of the daylight graph goes off the chart as it is never truly dark. In Shetland it is even more pronounced and is called the ‘simmer dim’. In St Petersburg they have the ‘White Nights’.
At the other end of the year, in the depth of winter, from late November to late January the days are cruelly brief and the nights are truly dark because the sun spends most of its celestial journey sunk far below our horizon. It rises late, appearing briefly in the southern sky and shines at us almost horizontally at midday. This makes window blinds paradoxically more useful in winter than summer in northern latitudes. The shallow angle of the sun’s rays also makes the effect of clouds more pronounced in winter. If cloud cover is complete, the sun’s rays have to pass through much more of the stuff to reach the ground than in summer. Cloudy winter days are extra dark and we find ourselves putting the lights on at noon.
In winter, when still working in a windowless radiology department, I left home before 8am and returned after 6pm. This meant that for a couple of months it seemed to me to be dark all the time. Early February was a landmark, because that was the first time I found myself leaving the department in daylight since the previous November. Now that I have retired I notice the slight improvement as January wears on. We are more aware of sunrise and sunset in winter because we are awake to witness it.
The steepest slopes of the day length graph are seen between the solstices, in spring and autumn. Unlike at the solstices, these times are associated with pronounced changes in day length. These periods of rapid change encompass the equinoxes when day and night are equal in duration over the entire planet and the sun sits directly over the equator. The further north you are, the faster the change in day length. In Scotland the day lengthens or shortens by nearly 5 minutes a day around the equinoxes. Some parts of Greenland experience a 15 minute change in day length at those times. Unlike winter and summer, every day seems to bring a change in the light.
By chance our street runs almost exactly east to west. The back of our house faces south and the front, north. At the equinox the sun shines directly along the street at sunrise and sunset. As summer comes in, the points of sunrise and sunset migrate north, narrowing the angle between the two until their maxima at the solstice. The summer sun floods through the the windows on the north side of the house early in the morning and once again in the late evening. The reverse happens in autumn as the points of sunrise and sunset migrate south and the nights ‘draw in’ leaving the north side of the house sunless for six months.
These changes in daylight are astronomical and precise but the organic sensations down here on earth are out of sync with our star. My grandfather used to say, “As the day lengthens, the cold strengthens.” The seas around Britain take time to warm up and time to cool down. The ground has less thermal inertia than the water but it also takes time to adjust to the energy coming from above. This means that spring is colder than the equivalent time in autumn and the chill can extend well into June. After the summer solstice things finally start to warm up. Similarly, mild days in autumn can extend well into November as they have done this year. We are only about 6 weeks away from the winter solstice now but maximum temperatures are still in double figures. However it is also wet and windy, what Robert Louis Stevenson called ‘this dog’s weather’, from which there was no relief until after Christmas when proper cold set in. In RLS’s day this meant Duddingston Loch freezing over sufficiently thickly to allow skating. He described watching the skaters from the hill as they lit their torches at dusk. It must have been beautiful – but the loch rarely freezes now:
https://en.wikipedia.org/wiki/Edinburgh:_Picturesque_Notes
In Scotland we pay for our lovely long summer days with with the seemingly endless darkness of December and January. If only we could bank the excess daylight of summer, wasted on us while we sleep, and use it instead to dissipate the winter gloom.
The Bohemian Waxwing 