Day 17: In Which the First True Night Occurs

This one is mostly going to be astronomy and graphs.

I’m not at such a latitude (or such a time of year) that the sun hasn’t been setting; the sun has dipped below the horizon once every 24 hours I’ve been here, but there’s a wrinkle in how ‘night’ is defined, in part because there are 3 twilights that are important.

Entirely a tangent, but when I first found out about this, it felt like some fairytale loophole where you promise to stay somewhere for seven days and seven nights, but the sun never truly sets, so by the time you get home it’s been seven years. anyway, welcome to things I worry about sometimes.

stolen off wikipedia

Civil twilight is when the sky is still light enough to see by, nautical twilight is when you can see the horizon line and some bright stars (extremely useful for celestial navigation, a thing only sailors care about), and astronomical twilight ends when there is no light from the sun in the sky anymore. And since I’ve been up here, the sun hasn’t been 18° below the horizon until last night, when it actually got full dark.

I was surprised that I could actually tell the difference; it was actually darker last night than it has been, and the faint streaks of light near the horizon aren’t there anymore. It’s only gonna get darker until the solstice.

Speaking of, I decided to make a graph of how much daylight I have per day at this latitude:

The purple dot is today, roughly. What cracks me up is that this is roughly a sinusoid (I swear it looks more sinusoidal if you zoom in more), except for the summer where it goes Flat (because there is only so much daylight you can have in a day).

And then I started wondering what the slope of that daylight graph is (ie, how many minutes of daylight am I losing per day) so I made this graph:

Which made me start giggling hysterically because of course the derivative breaks on the flat bit. For some reason trundling along this curve at a solid negative 7 feels less doom and gloom (haha) than just falling down the slope of that first graph, even though it’s the same information.

I’ve also been going school, not just contemplating my astronomical position in the universe. This class is Marine Ecology and oh my god I’m so happy to be back in a hard(ish) science class instead of a social science. We spent most of today doing a transect of a rocky beach – counting algal species and snails and bivalves and trying to determine if the species distribution changes as a function of distance from the water (it does). I got to describe the sand and identify a whole bunch of snails and the sun came out towards the end and it was a lovely day.

Wednesday was a fish dissection lab, and while I have missed labs, I have not, as much, missed doing dissections. fish slimy. We cut their stomachs open to look at the contents under a microscope and I was amused to see there are copepods here too (the last time I saw copepods was the middle of the sub-tropical Pacific) but I guess those suckers will live anywhere. Seriously, one fish had over 200 copepods in its stomach. I counted.

One of the other kids in the program works at the local bakery and came by with end-of-day leftovers, so I’ve been indulging in chocolate covered doughnuts, a not bad cinnamon roll thing, and a whole pile of rosemary bagels. Delicious. I also finally found the baking aisle in the tiny local grocery, which means I can buy flour, so I branched out from making lasagna in the round* glass pie pan I borrowed from next door to chicken pot pie (also tasty, for all I think I accidentally put in half the water I was meant to in the crust. oops). *yes I have been making round lasagna with square noodles for the last week in a half, it’s only a little bit like an applied Riemann sum problem, it’s perfectly edible

2 responses to “Day 17: In Which the First True Night Occurs”

  1. Alice,
    I just love this whole thing so much: what you are going, how you describe it, and the fact that your sharing it so I can read it. The world is lucky to have you in it!

    Karin (from the next street over)


  2. love this description of the various twilights and when day begins and ends (or not 🙂


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