It was on a campsite in central Norway in the July of 2015 when I first learnt to appreciate astrophysics. Having arrived at the campsite late in the day with a tent that had been packed away wet that morning, I was keen to get the thing erected and dried. Modern tents do dry extremely quickly, even when not in direct sunlight, but a bit of sun doesn’t go amiss. The campsite in Norway was in the bottom of a valley and when I arrived, the sun was fast approaching the hill to the north west. I naturally assumed that before long the sun would disappear behind the hill and my tent would take longer to dry. But it didn’t. As I watched, the sun rolled down the gently sloping ridge of the hill heading north until it reached the horizon at which point, later that evening, it continued its journey out of view. This being only a month or so after the summer solstice, it only disappeared for a few hours before emerging again to the north east. My rash, unthinking assumption that the sun would fall vertically like a stone behind the hill, almost as if it were under the force of a celestial gravity, was of course completely wrong. I knew this anyway – the sun rarely moves straight up and then straight down (you’d have to be living at the equator for that to happen) – but it was the extent to which the movement was so much more – much much more – to the north than towards the horizon (which could only be described as a slow trudge) that astonished me. It was my first lesson in astrophysics and I think about it regularly when I glance to the sky and ponder the movement of the sun, especially on a day such as today when the autumn equinox approaches and, for the first time since March, the number of hours of darkness each day begins to outnumber the number of hours of sunlight. (The moon, incidentally, I have yet to fathom…)
