Day 14 - Age of Exploration

Day 14 - Age of Exploration - 1 2 AGE OF EXPLORATION...

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1 1 AGE OF EXPLORATION 2 instruments - improving compass (knowledge transfer from China via Silk Road?) Remains 1565 Spanish compass; 1711 Portuguese mariner’s compass 3 for navigation. 4 shoreline with places, navigation lines on constant bearing 5 Land interior little detail 6 professional cartographers - 1375 John of Aragon commissioned map from Abraham Cresques as present for French king - Catalan Atlas 7 cities; mountains, rivers - but also image camel caravan 8 Map part of Asia (from Marco Polo’s descriptions), Africa mix accuracy coast of Africa; includes mythical “river of gold” flowing into heart of Africa 9 Africa from monk Fra Mauro 10
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2 by Marco Polo?) - oriented with south at top (common Muslim maps) 11 Detail - reasonably accurate even for Africa despite limits European exploration; one of earliest Western maps to include Japan 12 Map inaccuracies especially for ocean crossings - Columbus greatly underestimated length voyages - underestimate size of earth. 13 tables of measurement to calculate latitude using sun or North Star. 14 longitude problem - "dead reckoning” - measure distance successively from known point - “log and line” (calculate speed by unreeling line with knots tied in it) - errors compound 15 longitude - Galileo idea for using eclipses Jupiter’s moons - impractical crackpots - “sympathy powder”; ships anchored across ocean to fire cannons; 16 Idea for finding longitude using mechanical timepieces - 1657 Dutch astronomer Christiaan Huygens published ideas for pendulum clock, higher accuracy - but clock thrown off due to rocking of ship, 17 1707 British Navy returning from battle trying to reach English warships - due to navigation error, hit rocks off southern Britain, lost over 1400 men. 18 1714 British Longitude Act - reward 20,000 British pounds (fortune) Country carpenter (little formal education) John Harrison 1720s longcase clocks increasing precision - use tropical wood (natural oils
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3 reduce friction), brass-iron composite pendulum. 19
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This note was uploaded on 03/30/2008 for the course HIST 284 taught by Professor Bix during the Winter '07 term at Iowa State.

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Day 14 - Age of Exploration - 1 2 AGE OF EXPLORATION...

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