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.

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Well, if I can say something without jinxing it, it appears as though our two weeks of winter may be over. Not but what it won’t be grey and rainy for a while yet, but the incipient buds are swelling more greenly on their socially networked branches. The leaves cluttering the sidewalks are from the sweetgums, and most of them only just fell within the last month. We’ve had some sunny warmth here and there, and while I haven’t seen any hummingbirds yet, the Steller’s Jays have been joined by squads of robins.

But the thing that really brought a sense of seasonal change for me was at the end of the cold snap we had in December. Hardly seems fair of me to use that term, when Fairbanks has been pretty chilly by comparison, but people take notice when we get a weeks worth of heavy frosts in Corvallis. At any rate, on about 29 December, I woke to find cirrus clouds covering most of the sky, and causing a strong, beautiful 22 1/2 degree halo around the Sun. I’ve long since given up any pretensions to being able to photograph such phenomena, so I contented myself with staring upward for several blocks on the way to work.

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While I am interested in the news from the startup of the LHC, I think the event has already been well-covered by intellects vaster and with much closer knowledge than me.

Stay tuned for rhetorical analysis, though.

Laziness? Must be.

11 November 2007

Which serves two purposes, really. It excuses (or explains) my lack of posts, and saves me from having to come up with a better explanation (or excuse). Although it is possible that the sudden access to two good libraries within the last few weeks has diminished my online presence, save in card catalogues.

Anyway, I soon hope to be posting on religion debate rhetoric, drag show-influenced politics, tree identification, epistemology of Holocaust deniers, and the philosophy of quantum theory. Right after I summit K2, of course. Meantime, here’s a list of some good books:

On Literature, Umberto Eco–the essay on Borges and influence alone is worth the price of admission

Denying the Holocaust, Deborah Lipstadt–I learned more about the process of rationality from the first two chapters than from any other single book I’ve read

Envisioning Information, Edward Tufte–beautiful and needs to be read several times

Where the Suckers Moon, Randall Rothenburg–zany, educational, and bearing few points of reference to anything familiar (it’s about advertising) 

No TV is good . . . and bad

18 September 2007

Bad in the sense that I didn’t hear about the kerfuffle about a supposed Syria-North Korea super-villainous plan until today, despite numerous reports last week.

The money quote is right here, from Joseph Cirincione:

This story is nonsense. The Washington Post story should have been headlined “White House Officials Try to Push North Korea-Syria Connection.” This is a political story, not a threat story. The mainstream media seems to have learned nothing from the run-up to war in Iraq. It is a sad commentary on how selective leaks from administration officials who have repeatedly misled the press are still treated as if they were absolute truth.

Well, no tsunami yesterday, completing the trifecta of non-disasters. The potential here was anulled rather quickly, but it took a while longer to clear things in Chile. We did, however, have another earthquake last night. This one was centered, as nearly as I can tell, just a few miles northwest of our house. Also, again last night the clouds were at just the right elevation to be spectactularly illuminated by the 21 July fissure.

Anybody on this island looking for inspiration for literature from the natural world will not lack material for the latter half of August.

Beginning with the Perseid meteor showers starting sometime around 8 August and peaking on 12 August, there have been several routine (in the geologic or astronomical sense) yet remarkable (in the participant or observer’s sense).
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