Anatomy of a sunset

When I was involved in bird research projects, I would usually be up and arriving at the research site in the pre-dawn twilight to set up our equipment. One of the best things about having to get up so early – okay, the only thing – is that you would get to enjoy the sunrise every day (on those days where the sky wasn’t clouded over, anyway). I have some beautiful sunrise photos from that period. Pinks seem to predominate, though I have a number of striking oranges and reds, as well.

I was mildly disappointed that our new house faced east, such that we wouldn’t see the sunsets across the water, because I did really enjoy watching the colours of the sky. I knew that I was unlikely to be up often enough, at least in the summer and fall, to catch the morning sunrise that we would be able to see from our deck, but I am always up for sunset. I used to admire some that we would see from the apartment in Toronto, but would never take a photo. It just wasn’t an ideal setting, with all the buildings and power lines and everything else in the way.

I guess I hadn’t expected to be out in the boat so often here, or out so late. But some of the best fishing can be had at dusk, so we’ve frequently gone out just after dinner and stayed out till after the sun has gone down, navigating our return by the silhouettes of the trees and the reflection of the water, and tracking our location by the illuminated houses of our neighbours.

I think the best sunrise and sunset photos are those taken across water. It has the dual advantage of a large open space to give you a better view of the sky, as well as the reflective properties of the water that replicate the colours below. Since I’ve been fishing for the smaller guys, using jigs instead of cast-out lures, I really prefer to fish during the daylight hours; early morning is my favourite, when the lake is still and quiet, though it unfortunately requires setting the alarm to be sure I’m up. It’s easier to go out in the evening, you’re up anyway. My favourite part of being out late, after I can’t see my lure in the water anymore, is watching the sun go down and the sky light up.

The reason that the sky isn’t just the usual blue during sunrise and set is because of the angle the sun’s rays are traveling through the atmosphere at. If you move six hours east (in the case of sunrise) or west (for sunset), the sky will be blue under the sun there. It’s the same sun, just the angle has changed. At all angles, the light waves are encountering particles in the atmosphere, and are breaking up into their different components and scattering. The ones that head down to the ground are in the blue spectrum, which is why the sky looks blue. The reds and oranges get scattered sideways. At the very acute angles that the sun’s rays are viewed when the sun is near the horizon, it’s these reds and oranges that reach our eyes.

Almost inevitably, sunsets are more dramatic and more brightly coloured than sunrises. Since the sun is entering and leaving the horizon at the same angles, it’s the amount of dust and other particulates (like pollution) that affect the colours. The more particles in the atmosphere intercepting light waves, the more light that gets broken up and scattered, the brighter the sunrise and sunset.

The reason sunrises tend to be paler, then, is because there’s less in the air. During the course of the day, activity by people puts dust, dirt and pollution into the air; it settles out, to some extent, at night. Also compounding this effect is that as the sun warms the earth it creates convection currents – winds – that stir things up into the atmosphere as well. Clouds and moisture can contribute to bright displays, which is likely the meaning behind “Red sky at morning, sailors take warning; red sky at night, sailor’s delight.” A red sky at night is just a reflection of the day’s dust, but a red sky in the morning is probably reflecting off the particles associated with a storm system.

Of course, the sky’s colours can also be affected by natural events such as volcanic eruptions, large wildfires, or dust storms, which throw immense amounts of dust and particulates into the atmosphere, too much to settle out quickly. Some events are so large in scale, such as the eruption of Krakatoa in 1883, as to affect the atmosphere of the entire globe. Not surprisingly, though, and perhaps rather thankfully, these events are rare.

What we think of as a typical sunset doesn’t occur on planets other than our own. Differences in atmosphere composition and distance to the sun mean that the light refracts differently than it does in our own atmosphere. This is also why a blue sky is a novelty to our planet, and why the moon has no daytime sky at all (it lacks an atmosphere). High winds on Mars kick up sufficient dust high enough into the atmosphere to sometimes create a lingering red sunset that can last as long as two hours after the sun sinks below the horizon. However, without this dust in the air, the sunset there isn’t much to look at.

Another interesting sunset phenomenon is called the green flash. I’ve never seen it, and I’m unlikely to here. It happens just as the sun dips over the horizon, right at the cusp. The light waves break and scatter in just such a way, and the atmosphere is just dense enough at that angle, that for a brief period the sun’s rays glow green. They’re usually only seen on an unobstructed horizon, such as over a large lake or the ocean, or in the great plains. This is because the light needs to be traveling through the densest part of the atmosphere to create the effect, and this usually occurs close to the ground. Given all the forest surrounding us here I probably won’t be seeing one any time soon.

The problem with taking photos of things like sunsets is that you can amass a huge collection of them, since you’re tempted to photograph each and every one, because they’re all different. But then what do you do with them all? Well, I can share a few of my favourites from the last few weeks here, in any case.