Just a bit of background: We live at approximately 8 degrees north of the equator. The difference between our shortest day and longest day is about 30 minutes.
Now, here’s my question. Given that we’re so lose to the equator, and have a pretty small difference between summer & winter, why does the sun swing so far between the two seasons? This is by no means accurate or even remembered properly, but from sometime last year, when I am positive that the sun was just over a neighboring island when setting, to right now today, I held a tape measure at arm’s length (23 1/2 inches from fist to eyeball), and the length along the horizon was about 10 1/2 inches. I would have thought that the sun wouldn’t “swing” so far here…maybe an inch or two as measured by my ruler at arm’s length.
I mean, back when I spent a year and a half in Trenton/Princeton New Jersey, I observed some rather large swings of the setting sun from my motel window. But, they did not seem all that much larger than what I’ve observed here; yet the diff in the day’s length was very large.
Am I just nuts or is there a reason for this?
I think I just misremembered, but I was looking at some photos from last year, not sure just when they were taken, and the sun was definitely a lot further left than what it is now.
meh. This is so trivial I should have put in IMHO probably. Mods can move it with no trace of guilt. :o
Wherever you are in the world, the sun must swing about 46 degrees between the summer and winter solstices. It’s overhead at the Tropic of Cancer at the northern summer solstice, at the Tropic of Capricorn at the northern winter solstice. So your noonday sun altitude must differ by 46 degrees no matter what.
Being close to the equator (but still one-eleventh of the distance to the Pole) reduces the amount of what we’ll call “sunset swing”, but doesn’t eliminate it unless you’re at the equator. I don’t know the formula OTTOMH, but if your 10.5" swing seems a lot, bear in mind that at the Arctic Circle the swing would be the entire horizon. It’s pretty darn big here in southern England, about a half circle’s worth.
Sun ___N___
(summer) .-- --,
.' `.
/ \
/ . . \
| . . |
|-------- X --------|
| . . |
\ . . /
\ /
Sun `. .'
(winter) `--_______--'
S
If you are at the X, the summer sun disappears north of due west by 23.5[sup]o[/sup], while the winter sun disappears south of due west by 23.5[sup]o[/sup].
If it’s useful, here’s an image showing the swing. The solstices correspond to the end points of the figure-eight, and the two equinoxes are both at the nexus.
I remember some astronomy freebie program I picked up mid-Nineties that you could use for all sorts of things, including showing the path of the ecliptic as seen from any point on Earth, and at various simulation rates. It was quite fun to set the viewpoint at the Equator and crank the rate up to about a million times, and watch what the ecliptic did.
The equinoxes are of course on the halfway line of the figure. Here’s an illustration showing their positions.
The nexus point, where the curve crosses itself, has no special significance — so far as I know anyway.
I think H.G. Wells, in The Time Machine, had the Time Traveller noticing the sun fluctuate like that in the sky, as he hurtled into the distant future. Score a point to Wells for knowing some astronomy.
And subtract a point from me for forgetting some of it. (At least until I’d had my coffee.)
