A Day's Bookends
The making of a sunrise & sunset
A ray of light exploding from the photosphere of the sun has something like 498 seconds to meander through the cosmos at the brisk speed of c before it reaches Earth. If you happen to be located along the solar terminator at that moment, the ray will pierce the atmosphere at nearly a tangent to the Earth. What was a white ray of light in space will, if you’re lucky, be scattered, reflected, and diffused into sublime shades of red and orange. This is, in so many words, a sunrise or sunset.
Those of us living in the Front Range have been blessed recently with not only glimpses of the Northern Lights but also unusually good starts and ends to our days. This is no coincidence: winter sunrises and sunsets really are better, as I’ll explain (I take this small joy as some consolation in the Dark Times).
Sunrises and sunsets paint fiery hues across the sky because of the different wavelengths of visible light. White light travels through the atmosphere and is scattered by air molecules and particulates (“Rayleigh scattering”). Colors with shorter wavelengths (violets, blues, and greens) scatter more strongly than the longer wavelengths of oranges and reds. The increase in the amount of air mass light must travel through at sunrise and sunset, then, scatters out the blues and violets completely (and usually, but not always, the greens), leaving the amber skyscapes that I hope for on every predawn commute to go skiing.
When particulate matter like smog, wildfire smoke, or volcanic ash is trapped in the low atmosphere, sunsets are washed out because these particles scatter light evenly across the color spectrum (“Mie scattering”). Instead, you want all the “stuff” to be up high. The spectacular shades reported after large volcanic events, for instance, come from stratospheric pollutants blasted high into the atmosphere. The same goes for clouds: higher elevation clouds allow for reflection of the diffused light without blocking it from the viewer or washing out the light.
As we approach the winter solstice, the sun’s diurnal arc shortens. The sun’s low elevation in the sky means that light must pass through a thicker slice of the atmosphere for a longer time compared to the high solar altitude of the summer. Cold winter air is usually drier as well, creating less Mie scattering from water vapor. You can expect longer duration golden hours during the winter months, then, and more dramatic coloration.
Sunrises tend to be clearer and crisper as the air is cleaner in the morning. The colors can be more varied and muted, with some lavenders and cooler shades making an appearance. Sunsets tend to have more dramatic coloration as the day’s warmth creates wind that carries dust and other particles into the air, along with all of the aerosols caused by human activity.
Can you forecast good sunrises and sunsets? This Belgian CS student thinks he can, mostly based on cloud data. I’ll report back on the accuracy of the alerts!
Sunrises and sunsets, the bookends of our days, serve as potent metaphors. The daily dose of liminality is a reminder of changes in life.
I have a special affinity for sunrises. While everyone is awake for a sunset, sunrises feel privileged. Earned. When I think of being awake for a sunrise, I think of alpine starts on Kilimanjaro, or Humpback Rock, or Longs Peak; I think of the brightening horizon of the Atlantic off the Carolina coast; I think of new beginnings.
As of late, I’ve been wrestling with a number of transitions and realignments that feel like so many sunsets. And sunsets, beautiful as they are, often evoke a tinge of sadness. I face decisions about whether or not, and if so, how, to close a few chapters. Choices about doors to shut. Endings.
Facing the darkness of the night can feel like a scary proposition. But after every sunset, goes the truism, is a sunrise. And as I mentioned, I am partial to a sunrise.
I love local group chat commentary on sunsets, and now aim to cultivate more if it, following your lead.
In 1999, I paid $400 a month to share a two-bedroom apartment across the street from Stonesteps beach in Leucadia, California. (I was working part time at 7-Eleven and part time doing random roofing projects. I doubt a product manager at Qualcomm could afford that same apartment in 2025!)
Anyway, the best part of that particular neighborhood, at least back then, is that a crowd of 20-30 neighbors would gather to watch the sunset with their mugs of tea or a glass of wine. To our right, lined up along the cliff, were about 20-30 seagulls also staring straight ahead into the sunset. None of those neighbors became close friends, but it was so meaningful to just nod at each other and chit chat about whatever. A secular ritual silently appreciating the beauty of physics, grounded in local community.
The local group chat is a good runner-up, but I’d love to find a little sunset appreciation society here in Oaxaca to commune in silence and appreciation for five minutes each evening.