Happy September equinox, everyone.

One of the cool things about this day is that it has a fairly high profile on the common, demi-Gregorian calendar, the equinoxes perhaps figuring even larger than solstices in my casual surveys. Another one is that it is only the autumnal equinox if you live north of the equator: otherwise, it is the vernal kind.

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Wayfinding and waves

27 April 2009

I once had a brief discussion with a much smarter fellow than myself wherein he argued that four was an arbitrary number for cardinal geographic directions. While I concede (now, as I didn’t then) that he is correct from a geometric point of view, there seems to be at least one evident physical reason for the choice: one direction each for sunrise, sunset, and halfway from each to the other.

While Guy Ottewell gives a potential (if esoteric) thesis for why A is the first letter of a couple of different alphabets, I have nothing like the speculative erudition to say whether my guess holds any water. I do know, though, that while useful direction finding tools can be simple, they can also be arbitrary. Polynesian navigators use celestial coordinate systems shaped from the rising and setting of the Sun and other stars, and these coordinate systems are sometimes symmetrical and even, but not always. Navigators also shape their course based upon other information including clouds, wind, sea critters, birds, and other factors.

One of these other factors was brought into sharper focus for me as I flew from Minneapolis to Cleveland last week, passing over Lakes Michigan and Erie on the way. As far as I’ve been able to figure, this trip was at a similar altitude to those from Hilo to Honolulu, flying at approximately 30,000 feet. What struck me as different, though, was that while I was used to seeing the Pacific Ocean with increasing complexity as more and different sets of waves gradually revealed themselves crossing and rolling on its slightly rough skin, I didn’t see any texture of swells on the two Great Lakes.

Having grown up about six blocks from the edge of Lake Superior, and spent time tagging along on boats with my father from a tender age, I can attest that the Great Lakes do possess waves of sufficient size as to be seen from the air. Those waves might not be the sixty-foot seas of the northern Pacific that cause the weather announcers to doubt their script in the middle of reading it, or even the massive rollers that create the fantastic offshore breaks at Peahi near Maui or Mavericks off California, but Great Lakes waves have sunk ships and otherwise imposed their presence in plenty of ways. In short, I was surprised that I couldn’t see anything from the air, even on a relatively calm day.

My guess as to the cause is something called fetch. In this case a noun, fetch refers to the distance across the water that a wind blowing in that direction has to build up waves. While modeling the problem quantitatively is by nature more complicated, fetch can have an effect equal to that of the speed of the wind. It is the biggest reason why small lakes don’t have big waves. Wind speed and fetch can also affect the rate at which waves come in, their period, a characteristic well known and scrutinized by surfers everywhere.

I’ll do some checking with other resources, but I would guess that the tapestry of overlaid swells that help Polynesian navigators orient themselves on the Pacific was also present on Lake Michigan a week ago, and that the chief difference in appearance wasn’t caused by a difference in height of the waves, but rather in their frequency. Lake Michigan is long and thin, perhaps 85 miles wide from Milwaukee, WI on the west side to Grand Haven, MI on the east, but 280 miles north to south from rural Summer Island on the UP to industrial Gary, Indiana. Thus, when the wind is blowing most directions, there is fairly little water to build up long distances between waves. Only if the wind blows due north or due south (winds being named for the direction they are blowing _from_, in most cases) is their enough fetch to produce swells wide enough to be seen from the air.

Any kindly contributors with more knowledge are invited to comment, particularly if you have done some calculations. I am halfway through building a KML file for the trip, and will post it to the comments when it’s finished.

(mostly) Northern roundup

14 November 2008

Kyle Hopkins kicks ASS! Just heard him interviewed on NPR about an Alaska politics article he wrote for the ADN, and I was both thrilled to hear about someone I had lost touch with, and relieved that so sharp a wit is covering the important Stevens-Begich Senate race closely.

Begin obligatory election response: pretty weird that the three most hotly contested (or at least most drawn-out) Senate races were the three states I was most interested in: AK (see above), MN, OR. End obligatory election response.

I’m just starting Rashid Khalidi’s book Resurrecting Empire, which doesn’t seem designed to flagellate liberal guilt so much as actually educate a willing audience about colonialist history from the Eastern Mediterranean to the Indian subcontinent. A good book, and I liked it even more when I found out that he’s almost as dangerous as Bill Ayers.

National Geographic has a ten-page cover article on light pollution out this month, and we happily have our first clear night in about two weeks (not that that’s a record or anything–Alicia tells me that she remembers Kodiak going for something like sixty straight days of rain once, and nobody was talking about records being broken) Still, though, it is crisp and cool tonight. Jupiter looked bright until I saw Venus, and Manaiakalani is setting in the west as Ke ka o ka Makali`i is rising in the east. Even though I know something about how bad light pollution really is, I am reassured that I showed my nephew the same two planets and some of the same stars from the East River about a month ago.

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The only constant in my life for the last month or so has been the ecliptic. Amid a ridiculous whirl of packing, helping others pack, preparing for a serious job interview, travelling, apartment hunting, mending fences at work, and sundry other things, I have tried to keep my eyes on the planets at night.

My friends can attest that with little or no provocation, I have been pointing at the night sky with a silly grin on my face and saying “Venus,” or “Jupiter,” or “Saturn.” These celestial non sequiturs are tolerated with polite indulgence and mild shaking of their heads, but they make me feel better. And recently, when Elle and I flew to Oregon where I spent a week before I reluctantly glided back on my own, the lineup of the aforementioned balls of cosmic dirt, together with the waxing gibbous moon, were the only things that kept me centered.

It turns out that I didn’t get the job I interviewed for, despite copious preparation on everything from sprinkler heads to rat catching, as well as thoughful and intense interview prep from some very well-qualified friends. Ah, well. Keep looking, and in the meantime head to the summit today.

For any astro-types out there, check out Stellarium, an open-source planetarium application. It is typically light on features, but has a very nice aesthetic (a feature too often overlooked, in my opinion) and has at least a few Hawaiian star and constellation names, making it one of an even smaller category, as far as I can tell.

Bird types aren’t so lucky, since I don’t have a website for you, but you’ll no doubt be amused by my sheer joy in seeing turkey vultures and crows in abundance. No doubt I’ll get over it.

Hōkūle‛a and Maisu are getting ready to depart Pohnpei for Chuuk today (or tomorrow, since I still have trouble with the dateline where today is 5 March on our side of the dateline, and 6 March on their side).

Gary Kubota of the Honolulu Star-Bulletin is crewing for this leg of the voyage, and has an excellent brief article on the effects of current and projected sea level rise on Pacific Island nations, specifically the FSM.

If any kindly contributors can suggest a better way to correctly get the Hawaiian characters in to the Camino browser, I’d be grateful.

Continue below the fold for another update by Rod Floro, crew member on Maisu.

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I recieved an email from my friend Rod Floro, a science teacher at Kea’au Middle School who is spending the next several weeks at sea as a crew member on the Alingano Maisu. As with any trip, Rod experienced problems with the airlines and new language at the destination when he flew from Hawai`i Island to Majuro in the Marshall Islands.

According to the PVS website, the voyage from Kealakekua Bay to Majuro lagoon was about 2200 miles and 26 days. One of the first actual signs of land (other than the knowledge of the navigators) was a sighting of birds (manu o ku or white terns) which can range out about a hundred miles from land during the day. Also, Google Maps has much better pictures of Majuro available than they did a couple of days ago.

Below the fold is a bit of Rod’s email–enjoy.

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