Seeking Seeking the the LongitudeLongitude300 BC-AD 1675300 BC-AD 1675

Reading 2004 SpringReading 2004 Spring

Questions:

The Difficulty of Determining Longitude?

The methods of determining the longitude?

What events about the story of longitude happened in the Middle Ages?

Latitude/ longitude In contrast to latitude, the means

of accurately calculating longitude at sea was long elusive.

Not until 1714 was there an accurate way of determining longitude even on land, let along at sea where waves made accurate measurements difficult.

Sailing in the uncharted oceanSailing in the uncharted oceanThe best that sailors could do was

to calculate their displacement east-west by using a process of intelligent guess work called "dead-reckoning." Given that this ‘reckoning’ had to be adjusted for the effects of wind and sea in carrying a ship off-course and that these effects (called leeway and drift respectively) could not be accurately and reliably measured it was, as Quill (1966:2) observes, "a most hazardous way of navigating."

longitude ("meridians") On the globe, lines of constant

longitude ("meridians") extend from pole to pole, like the segment boundaries on a peeled orange.

Longitude lines or "meridians"

Greenwich Meridian:

Meridian comes from a word meaning "Middle". The Greenwich Meridian was set at the Greenwich observatory, in Greenwich, England to be the geographic point for where East and West meet. Therefore, Greenwich Meridian is indicated as 0 ° latitude. The world time standard is set at Greenwich observatory, and all other time offsets (in terms of time zones) are calculated from Greenwich Mean time (GMT), or Universal Time (UT), as it is often called . http://www.adventist.org/sun/help/#7

Explore the Ocean The oceanographic metaphor The ocean, literally the

unknown world of the earth the unknown world of the cosmos macro-cosmos and macro-cosmos

Time and space In Hellenistic times, these

geographic quantities were usually thought of in terms of time, in number of daylight hours on the longest day of the year in the difference in local time between two places for longitude differences east or west.

Babylonian clay tablet world Babylonian clay tablet world map, map, 600 B.C600 B.C

http://www.henry-davis.com/MAPS/Ancient%20Web%20Pages/103.html

History Ancient (Greek or classical)

Ptolemy: Almagest and Geography

Hipparchos: The Lunar-eclipse method

The Middle Ages The age of discovery

Compass and navigation The chronometer method

Geography in the Middle Ages

China continues to be far ahead of Christian Europe

Geography a vehicle for Christian propaganda in Europe

Muslim translation of Greek works The Norse sailing to Iceland,

Greenland, North America

Ancient Influences on Medieval Geography

Plato (428 - 348 BCE) Aristotle (384 - 322 BCE)

climatic zones Ptolemy (85 - 165 CE)

geocentric model of the universe

Ptolemy's map of the worldPtolemy's map of the world. .

Now the main part of Geography consisted of maps but Ptolemy knew that although a scribe could copy a text fairly accurately, there was little chance that maps could be successfully copied.

He therefore ensured that the work contained the data and the information necessary for someone to redraw the maps. He followed previous cartographers in dividing the circle of the equator into 360 and took the equator as the basis for the north-south coordinate system.

Eratosthenes' map of the worldEratosthenes' map of the world. .

Paucity of Geographic Paucity of Geographic knowledge in the Middle knowledge in the Middle AgesAges

During the Dark Ages, those five During the Dark Ages, those five centuries that followed the destruction centuries that followed the destruction of the Roman Empire, only very of the Roman Empire, only very limited, if any, information is available limited, if any, information is available about the navigation techniques of the about the navigation techniques of the time. It is presumed that sailors relied time. It is presumed that sailors relied on their powers of observation and sea-on their powers of observation and sea-crafts. Their skills are exemplified by crafts. Their skills are exemplified by great navigational feats by Vikings and great navigational feats by Vikings and Irish.Irish. http://rubens.anu.edu.au/student.projects97/naval/

The Deterioration of Mapping 1493 T - O Map Translation

Mappae mundiMappae mundi Medieval world maps are mental Medieval world maps are mental

maps. maps. They are composed by They are composed by

geographical experience, literary geographical experience, literary knowledge and philosophical knowledge and philosophical speculation. speculation.

The three continents of medieval The three continents of medieval world, Asia, Europe, and Africa, world, Asia, Europe, and Africa,

Interpretive redrawing of the Interpretive redrawing of the St. Sever Beatus world mapSt. Sever Beatus world map

Cosmas Indicopleustes' world Cosmas Indicopleustes' world picture, ca. 560picture, ca. 560

The CrusadesThe Crusades 8 separate crusades

between 1096 & 1270

Extensive travel over sea & land from all parts of Europe to the Holy Land

Popular description & travel was geography

Marco Polo 2 brothers & a son

Nicolo & Marco Maffeo

Traders, not Geographers

1271 - 1295 To China by land To Venice by sea

The Polo’s Journey

Bright Spots in Medieval Geography

William of Conches (1080-1154) philosopher & theologian translated Arabic work modern ideas concerning

heating of the atmosphere from below formation of clouds by cooling air

Robert Grosseteste, Bishop of Lincoln (1175-1253) also an Arabic speaker refuted Aristotle’s climatic zones taught Roger Bacon

The The CatalaCatalan n World World Map / Map / ca ca 14101410

An example of An example of Gemma Gemma Frisius's Frisius's triangulation. triangulation.

Mercator's world mapMercator's world map..

Of course the Mercator projection Of course the Mercator projection has the property that distances near has the property that distances near the poles are greatly distorted so it the poles are greatly distorted so it was not easy to use the map to was not easy to use the map to measure distances. Gerardu measure distances. Gerardu Mercator gave instructions on the Mercator gave instructions on the map so that for two places if one map so that for two places if one knew any two of the following four knew any two of the following four pieces of data: pieces of data:

difference on longitudes,difference on longitudes,difference in latitudes,difference in latitudes,direction between them,direction between them,distance between them, distance between them,

Petrus Roselli, 1466, Majorca

Portolan Charts From “portolani”

pilots or rutters Portolan chart

network of lines coastlines place names scale of distance compass shoals, reefs,

islands

List of places distances directions conditions at sea port dangers safe anchorages

Albino de Canepa, 1489, Genoa

Map of Medieval Universities

http://historymedren.about.com/library/atlas/blatmapuni.htm

http://historymedren.about.com/library/atlas/natmapuni.htm

This map is from the Historical Atlas by William R. Shepherd, published in 1923; p. 100.

Olaus Magnus, 16th century

1st large scale map of a European Region

LongitudesLongitudes

http://rubens.anu.edu.au/student.projects97/naval/

more web pages. . http://www-gap.dcs.st-and.ac.uk/~history

/HistTopics/Longitude2.html http://www-gap.dcs.st-and.ac.uk/~history

/HistTopics/Longitude1.html