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December 03, 2018


True confessions: I fixed some typos after first pushing "Publish." That pushed the time of publication past midnight to December 3, whereas the references in the post assume that "today" is December 2.

Well it was for a while.

When I was in the military, I spent a year in Iceland. For a time I was a member of the color guard that raised and lowered the base flag at sunrise and sunset each day. At the summer solstice, we would arrive a few minutes before midnight and lower the flag when the sun dropped below the southern horizon. A few minutes after midnight, the sun reappeared and we would raise the flag. At the winter solstice, it was a few minutes before noon and after. The times changed almost every day the rest of the year. The military is a stickler for process.

I fucking love winter, when the last remaining wilderness comes down out of the north and temporarily reclaims its rightful demesne.

I had an evening paper route in northern Iowa when I was a kid, and spent an hour between 4 and 5 every day tramping a couple miles along the winter streets as the sun set. After dinner we'd hike over to one of the ponds for nighttime ice-skating.

Temperatures over 80 F I can't stand without a lake to swim in.

Forgot to put this at the end

Obligatory books :
The Red God's Call by Paul J. Errington
Never Cry Wolf by Farley Mowat

Just popping in to say I love this post and I'm ok, it is just that real life showed up at my door and is kicking my butt. Not sure how so many deadlines and commitments could magically coalesce like that, but some of the things are good, but take me away from trying to post anything.

the strange pattern of sunrise and sunset, compounded by DST, confounded me, too. the “equation of time”, is what i was told it's called.

I have once or twice given myself a literal headache trying to picture all the motions that underlie that fact (this is related to why I didn’t enjoy the planetary astronomy class….).

Isn't it simply a matter of the tilted axis (with a bit of distortion from the eccentricity of the orbit)? Not that it's easy to visualize, but I didn't think there were that many motions involved.

Intuitively, you (or at least I) would expect not the analemma (https://en.wikipedia.org/wiki/Analemma) as it exists, but a straight line representing the position of the sun in the sky at a given point in (solar) time in the day over the course of the year. As it is, you get a funny-looking figure-eight-like thing. (With a circular orbit, it would be symmetrical vertically and horizontally. With the orbit we have, you end up with the sunrise/sunset effects in winter and summer not being quite exact inverses, with a bottom-heavy, kind-of-tilted analemma.)

hsh's link goes to Analemma) (sic), with nothing found. But if you put Analemma in the wikipedia search box, without the closing parenthesis, you get to what he was trying to link.

I had to cut that last comment short for reasons I won't get into.

The visualization I once saw involved a basketball on a turntable with a laser pointed directly at it's center at the midpoint of the height of the basketball. The basketball is placed on the turntable with one of the lines that would effectively be it's equator at a 23-degree angle relative to the plane of the turntable. An ant would walk along this line at the same angular velocity as the turntable would turn, but in the opposite direction, such that the ant would be stationary and the laser point would be on the ant the entire time if the line weren't at an angle with the turntable.

With the ant walking along the line at an angle, the ant would go above and below the laser point as the basketball turned, as you would expect. But, at the same time, the ant would also fall behind the laser point during part of the motion, but catch back up and get ahead of the laser point afterwards, only to fall back behind, and so on, forming a figure-eight relative to the laser point.

From the Wiki article on Analemma:

The north–south component of the analemma results from the change in the Sun's declination due to the tilt of Earth's axis of rotation. The east–west component results from the nonuniform rate of change of the Sun's right ascension, governed by combined effects of Earth's axial tilt and orbital eccentricity.

Axial tilt, orbital eccentricity, and may I point out, rotation to boot, because I'm pretty sure that plays a part in the fine-tuning of sunset/sunrise times as well. If you (hsh) think that's "simply" a matter of the tilted axis, then your definition of simple is different from mine.


"Simple" seems to vary. A lot.

I bet most of those here, being IT careerists, consider CoBOL to be simple. But there's a world of people out there who consider any computer language to be arcane at best. (Now with Assembler, they might have a point...)

And we've all noticed people, native speakers at that, for whom English spelling and grammar are apparently far from simple. I shudder to thing what they would do with a really complex language. Gender and cases for nouns, alone, would totally defeat them. Never mind French spelling.

So someone finding visualising a mix of rotation and revolution difficult? Hardly surprising.

Should have said: this is indeed a great post, but, regarding "simple", as soon as I read hsh's ant thought experiment my mind shut down. It reminds me of my (highly intelligent and creative, but very dyslexic and dyscalculic) sister, saying that all she has to read is "If it takes 2 men 3 days to...." and her mind shuts down in panic. Never useed to be the case for me, but (for whatever reason) seems to be now. Ah well, as they say here, horses for courses.

So someone finding visualising a mix of rotation and revolution difficult? Hardly surprising.

I find it difficult to visualize, so it's not at all surprising to me. I just don't think of it as being a matter of a large number of motions (particularly because I think of rotation as a given, since we're talking about sunrise and sunset at all).

That said, I do some fairly intense cardio during my lunch break, and when I have something to ponder, I find I can ponder it fairly deeply and continuously while exercising. It's a double-bonus, because my thinking hard about something other than the fact that I'm exerting myself makes the workout go by mentally a lot faster. Today I thought about the axial tilt, eccentricity of orbit, and rotation of the earth (or Earth?).

After pondering some more, I'd would revise my original statement, specifically regarding the non-coincidence of earliest/latest sunset with latest/earliest sunrise on the winter/summer solstice. Without eccentricity of orbit, you would still have equation of time effects over the course of the year from axial tilt, but the solstices and equinoxes would occur when mechanical time and solar time were lined up, resulting in earliest/latest sunset and latest/earliest sunrise happening on the same day, that day being the winter/summer solstice.

That is my theory, and it is mine.

What wj said. And don't forget tilt, along with rotation and revolution.

I'm lousy at visualizing in three dimensions; I found the Rubik's cube beyond frustrating. So obsessing on planetary motion is really self-torture for me.

As to language difficulties, I would say yes, and never mind French spelling when we've got English to entertain ourselves with, e.g.:



and lots of other spelling/pronunciation traps for nonnative speakers.

That first list doesn't even include the increasingly common pronunciation "shtr" for "str" -- google it and you can find lots of commentary.

Here's what kind of twists my head: as it stands, the earth is closest to the sun (perihelion) at a time very near the winter solstice in the northern hemisphere and furthest from the sun (aphelion) at a time very near the summer solstice in the northern hemisphere. What would happen if those points occurred near the equinoxes rather than the solstices?

My guess is that the analemma would end up being a loop of some sort (an ellipse or circle or some such) rather than a figure-eight. You'd end up with earliest/latest sunset and latest/earliest sunrise more or less coinciding, but sunrise and sunset times during the two equinoxes being very different, despite both having 12 hours of daylight.

That is my other theory that is mine.

hsh: Glad this post got you going. :-)

Later, when I'm not supposed to be working, I'm going to try to think your theories through.

hsh: Glad this post got you going. :-)

Indeed! Considering your OP and what you said about being more sunset-oriented, imagine how much weirder it would be in my proposed scenario with perihelion and aphelion occurring on the equinoxes. If I'm right about how that would go, you'd have a late-day equinox and an early-day equinox, one of which you would like and one of which you wouldn't.


your experience shows mainly that the US military doesn't do a lot of things in the far north. What you describe is extremely impractical. In Finland, the Defence Forces simplify the almanac mightily: the flag is raised at 6:00 or 8:00 and lowered at 21:00, unless the sun rises later or sets earlier. (And if the flag is lit, it is flown this way even in the winter.) This allows you to organise, during the warm months, pretty nice and uplifting flag-lowering ceremonies: the colour arrives and is paraded, the brigade commander inspects the brigade and gives a speech, an evening prayer is held, an anthem sung and finally the flag is lowered while sun is already low. Having sun "set" at an appointed time makes scheduling straightforward.

As to language difficulties, I would say yes, and never mind French spelling when we've got English to entertain ourselves with

Reminds me of the old joke:

Foreign language student gives up in despair and goes home when he reads the headline "Hamlet pronounced success!"

In civilised nations, a similar means is used in deciding when the sun is
over the yardarm...

In Finland, the Defence Forces simplify the almanac mightily: the flag is raised at 6:00 or 8:00 and lowered at 21:00, unless the sun rises later or sets earlier.

I think most stateside bases set reveille and retreat at 8:00 and 17:00. I seem to remember 6:00 at some of the bases I was on. The situation I described may have just been peculiar to that command. The upside of it was that, near midsummer and midwinter, you only had to turn out for color guard once a day. You could sit around drinking soft drinks/coffee and BSing until it was time to trot out and reverse what you did a short time before.

Your theory is confirmed by the analemma on Mars. Google that 3-word phrase, and you'll see.

I tend to take anything remotely related to physics on faith.

That said, I think I once saw the sun go down and up again in a span of just a few minutes and I had the impression that this all happened north of me. The setting part was to my right, so eastward and the rising to my left,the west.

I was in a tent in the parking lot of a truck stop about thirty kilometers south of the Arctic Circle at the time. I think it was sometime in July.

Any way I was obviously confused because no combination of revolution or rotation would cause what I saw. I think I mostly was experiencing insomnia because I had gone for three days with no real sleep due to excessive amounts of sunshine all the damn time.

I like winters, especially now that smoke from the end of the world is the new normal for west coast summers.

Your theory is confirmed by the analemma on Mars. Google that 3-word phrase, and you'll see.

Kewl! Thank you.

So, just to kick the dead horse one last (let's hope!) time, I have to revise my previous theory. Even without orbital eccentricity, earliest sunset and latest sunrise would not occur on the same day (or on the solstice). Mechanical and solar time would be aligned, but solar noon would be still be shifting as fast as at any time in the year. The difference in solar time and mechanical time is sinusoidal. The value would be zero, but the slope would be at it's maximum (or minimum, depending on how you look at it). Solar noon would be getting later, causing both sunrise and sunset to get later from some point not terribly long before the solstice until some point not terribly long after the solstice. Those two point just wouldn't be exactly the same points that they are with eccentricity added to the mix.

That is my modified theory that is still mine.

I don't think this counts as kicking the dead horse again, since I'm not putting forth or modifying another theory about the relative motion of the earth and sun. It might count as poking the corpse of a dead thread, but I can live (or at least reanimate) with that.

I had a dream that I was on some kind of waterborne vessel, seemingly on the Delaware River near Philadelphia. I was traveling with a number of people who, at least in my dream, were known to me. It was nighttime, and I was in bed in shared quarters. I awoke to look out the window.

What I saw in the sky was something like a long-exposure photograph of the night sky at one of the poles, where the paths of the stars form concentric circles centered directly overhead. In the case of my dream, it was some rare phenomenon that occurs very rarely in non-polar regions, though the circles are not centered overhead, but at some other inclination above the horizon. (Not that the sky ever looks that way anywhere, but only in photographs of the right kind.) What made this instance even more rare was that it coincided with a new moon.

Being a dream, things didn't really make sense, though the nonsensical nature of what was happening didn't occur to me while experiencing the dream.

As it turns out, if the path of the new moon enters the area of the center of the concentric circles formed by paths of the stars, it will become momentarily illuminated like a full moon. (Why a new moon would be in the night sky opposite the sun in the first place is one aspect of the nonsense of the dream. Why its being in that location would cause it to be illuminated is another.)

I awoke at the precise moment necessary for me to witness this incalculably-rare astronomical phenomenon. I tried to awaken the others sharing my quarters, but it was too late. The spectacle was over.

Later in the dream, I was telling my deceased father how I woke up for no particular reason at just the right time to see illuminated new moon and how unlikely it was for that to happen. At no point in my dream did it occur to me that my father was no longer living.

At any rate, I attribute this dream to my participation on this thread. (I guess that's another theory of mine, though one of a different nature than the others mentioned previously.)

Having just had a protracted discussion about calculating the weight of paint on aircraft with my aerodynamic engineer father, I am wholly incapable of even attempting to process this sunrise/sunset thing. Ok, full disclosure, I’m probably incapable of processing it even under optimal conditions.

So I’m gonna focus on the last part of the open thread thing. For me, it’s heading up to Maine this coming week. Northport, Camden, Hallowell, over the course of a week. Just throwing that out there for any ObWi-ers who may find themselves proximal. Drinks on us for anyone who cares to self-identify.

Then down to Long Island to said engineer for the actual X-mas thing. A fire in the brick fireplace (built entirely by said engineer & his brother who were union masons in their high school days) which, incidentally, was another discussion about calculating stresses and proper mortar mixtures for such. We are an exciting bunch!

Sounds kind of perfect, Pete (if you have some stuff to read)! Wish I could join y'all, but I'm here in the rainy, slushy, miserable mid-Atlantic. It could be worse, of course.

Pete -- It's possible I could meet up with you in Hallowell, depending on timing. Is it okay if I write to you via whatever email you use when you post comments?

Please do!

Some of my own thoughts about the winter solstice over at one of my many sporadic blog projects.

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