Longitude + pedagogy

This, I guarantee it, will be boring.  Just skip it.  It's a note for myself because I'm taking a class in pedagogy.
It's not that this is a new concept for me, but we hear a lot about how one learns - The key is that the new knowledge should be meaningful to the learner.  Try "learning" this: Zer tuga mon yugo.  Herdsl thiz soditgh cotlld.
Ha ha.
     So, what is meaning?  It grows from anything that, for whatever reason, seems relevant to the learner.  Maybe it was something that produced an epiphany - or maybe it was boring, but at least it followed a pattern that you understand (as in learning a new regular verb in French).  Behind this "meaning," in other words, is a learner who is able to connect that knowledge to something.
Once in awhile I'll read a book that answers a question I didn't even know that I had - and then it seems so vital to me to learn it.
     For example (and I'm wondering if other people find this incredibly boring) - I couldn't get enough of a book by Dava Sobel, Longitude: The True Story of a Lone Genius Who Solved the Greatest Problem of his Time.  It's very simple: before about 1760 sailors didn't have any feasible way to figure out their longitude at sea - so they had to travel by latitude... Hence the phrase "sea lane" which refers to the safe latitudes at which ships traveled.
     When I read that, I understood more about WHY the Spanish were so vulnerable to pirate attacks at sea on their journeys to America.  Sobel doesn't even talk about this... But, the light bulb lit up for me; Spanish captains couldn't take advantage of the vastness of the ocean to avoid attack.  The Brits could sit and wait for them.  Actually, much of piracy meant attacks on land - British, French or others attacked Spanish colonial cities which were accessible by sea - so - maybe my new "understanding" needs more research.
     Still, this idea of sailing without longitude, led me to colonial trade policies.
     In general, greed, bureaucracy, even cultural norms regarding labor or land or honor or wealth all partly explain the rigidity of the Spanish trade laws, but another part was the fear of losses caused by pirates.  In the end, one begins to understand that this hyper-regulated trade system was a reflection not just of a Spanish mind-set, but also of a technological limitation.  (Without claiming it was a direct result of the advance in navigation across the sea, the second half of the XVIII century ushered in a gradual opening up of trade for the Spanish colonies by the new royal family of Spain).
     So, the book about English policy and the history of science didn't transform my vision of the Spanish colonial period in America before the mid 1700s but it enriched it.  And I will remember much of what I read in Sobel's book.
If  I could find this sort of "AHA" book or moment for all my students. . .

. . . . . . . . . . . . . . . . . . . . . . . .NOTE: Why couldn't they measure longitude at sea?. . . . . . . . .

Lines of longitude are arbitrary or imaginary.  Latitude, think about it, is about a specific distance from equator and the poles, right?  The position of the stars or the sun at noon tell us a lot regarding our position relative to the equator (and sailors had charts that helped them translate that info. to latitude). Let's see if I can clarify.  At noon the sun will be directly above one, but it's course across the sky won't go directly through the middle of one's sky.  So, to see latitude we measure it's position relative to the middle of the sky (or to the position it would take on the equator).
In longitude, I need to know that same difference - where the sun is for ME at a certain time relative to where it is in Greenwich, England (see what I mean about arbitrary).  It gets complicated because when the sun is at a certain point it is noon, but that point is reached seconds or minutes apart depending on where you are on this rotating earth.  (Before time was standardized it might be noon in New York City but 11:56 in Pittsburgh.) To calculate longitude, you need to know the DIFFERENCE between your local noon and noon in Greenwich.  As amazing as it seems now, it was as simple as a reliable time piece, one that could work in the rocking humidity of a ship.
Okay - I'm going to add an impressive anecdote from the book some day (whenever I find my copy).  --> Finally! (March 2011) found some old notes I wrote after reading the book: 
p. 27 March 7, 1741, a British ship leaves patagonia w/ holds already stinking of scruvy.  Anson sailed the Centurion through the straits Le Mare, from Atlantic to Pacific Ocean.  As he rounded tip of Cape Horn, a storm blew up from west - 48 days.  Anson holds his latitude until he figures he's gone 200 miles westward. So finally Anson sails north and hits Tierra del Fuego. 
Primary competition for using clocks to figure out longitude is using night skies.  Position of moon in relation to stars at what time.  A lot of progress in this line of work.  Moon's position is tracked faithfully for years (Minimum would be 18 years).  This works -->quadrant --> sextant --are instruments that use celestial bodies.  But it's HARD to do these measurements, errors. 
p. 26 This research also leads to being able to see speed of light (nobody had ever been able to see it because no measurements have involved light far enough away).  The time was going to be calculated by looking at eclipses of Jupiter's moons.  They have very regular eclipses.  If you know the time they are happening one place... (Galilleo - died 1642). When Jupiter is closest and when Jupiter is farther - the eclipses would differ by at leat 4 minutes.
1714 NAVIGATION ACT prize $$ is never officially collected.