Lesson Outline

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Lesson Outline
I. Early Discoveries
II. The Middle Ages
III. The Age of Discovery
IV. Early Scientific Exploration
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The History of Oceanography
The modern branch of science known as
oceanography is of relatively recent origin.
Because the ocean is central to so many human
endeavors, by providing food and goods, trade
routes for their distribution, naval power, and
exploration, a great deal of knowledge of the
ocean has accumulated over the last two thousand
years.
A review of the history of oceanography involves
discoveries in numerous fields by men who would
not have been called oceanographers in their
time.
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Early Discoveries
Pytheas (c.380310 BC). Greek astronomer,
geographer, explorer.

• first Greek to visit and describe the British
  Isles and the Atlantic coast of Europe, possibly
  traveling as far north as Iceland and Norway.

• established a method to determine latitude.

• the first to recognize that the rise and fall of
  the tides were associated with the phases of the
  moon.

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Early Discoveries
Erastothenes (c. 276 - 195 BC). Greek
mathematician, philosopher, astronomer, and
geographer.

• measured the tilt of the earths axis by 23.5
  degrees, which gives us the seasons.

• calculated the circumference and radius of the
  earth.

• His estimate of the circumference, 40,000 km, was
  off less than 0.1

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Early Discoveries
Strabo (c. 63 BC 24 AD). Greek historian,
geographer.

• observed that the face of the earth was in a
  constant state of change. While volcanic
  activity was building new mountains, rivers were
  eroding the land back down.

Seneca (c. 4 BC 65 AD). Roman philosopher and
statesman.

• the first to call attention to what we now call
  the Hydrological Cycle. He observed that rain
  fell on the land, then ran down into the sea, but
  the sea did not fill up, and concluded that water
  was somehow returning to the air to fall as rain
  later.

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Early Discoveries
Ptolemy (c. 90 170 AD). Roman geographer and
astronomer.

• first proposed the use of grid lines on maps that
  cross at right angles. These later became known
  as latitude and longitude.

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The Middle Ages (3001500 AD)
Two important advances
(1) Arab traders obtained the magnetic compass
from the Orient, and introduced it to the western
world.

• Prior to this discovery, ships could not sail out
  of sight of land. With the compass, mariners
  could sail in any direction, night or day, and
  have no fear of being unable to return.

• The first compasses were made from a type of
  magnetic rock called lodestone suspended on a
  long string, so that they would always point to
  the north.

• Later, the magnet was floated in oil with a glass
  top and points around the face marked for
  accurate navigation.

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The Middle Ages (3001500 AD)
Two important advances
(2) The voyages of the Vikings.

• The Vikings were a war-like people living in the
  area of the North Sea.

• They built ships with both sails and oars, and
  became very proficient at burning and pillaging
  coastal towns.

• Just before 1000 AD, Viking captains sailed out
  into the North Atlantic, conquering Iceland and
  settling Greenland.

• In the late 900s, Leif Erikson actually sailed
  over to North America and spent a winter in
  Newfoundland.

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The Age of Discovery (late 1400 middle 1500)
After a millennium of little new knowledge of the
sea and the continents, we then had a great
amount of discovery occurring in a relatively
short span of time.

• Prior to the mid 1400s, trade goods like spices,
  tea, and silk came over land routes from India to
  Constantinople, then to western ports.

• After Constantinople fell to the Ottoman Turks in
  1453, trade between the Mediterranean ports and
  the rich trade areas of Asia became uncertain.

• This started a frantic search for an alternative
  trade route to India by sea.

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The Age of Discovery (late 1400 middle 1500)
Prince Henry of Portugal (13941460)

• recognized the need for accurate maps and charts
  if new trade routes to be found.

• established a marine observatory to bring
  together navigators, chart makers, astronomers,
  and retired ships captains to pool their
  knowledge and draw charts of the known world
  oceans.

• these charts provided the starting point for many
  of the voyages to follow.

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The Age of Discovery (late 1400 middle 1500)
Bartholomew Diaz (14501500)

• Prior to 1486, no one knew for sure whether
  Africa extended down to the south pole.

• In 1488, Diaz became the first captain to sail
  around the Cape of Good Hope at the southern tip
  of Africa.

• Diaz went no farther than just around the Cape,
  having shown that it was possible, before sailing
  back to Portugal.

• Diaz later participated in the discovery of
  Brazil.

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The Diaz Expedition
The early Portuguese navigators, endowed with
patience, were more than sixty-nine years
struggling to round this cape before they got as
far as Algoa Bay, and there the crew mutinied.
They landed on a small island, now called Santa
Cruz, where they devoutly set up the cross, and
swore they would cut the captains throat if he
attempted to sail farther. Beyond this they
thought was the edge of the world, which they too
believed was flat and fearing that their ship
would sail over the brink of it, they compelled
Captain Diaz, their commander, to retrace his
course, all being only too glad to get home.
(Excerpt from Sailing Alone Around the World, by
Joshua Slocum)
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The Age of Discovery (late 1400 middle 1500)
Vasco de Gama (14691524)

• retraced Diazs route around Africa, and then
  sailed up the eastern African coast to India.

• this established a trade route that was to be
  used extensively for the next 500 years, mainly
  by the British and the Dutch.

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The Age of Discovery (late 1400 middle 1500)
So now traders had a sea route to India, but
there were still problems

• Sailors had to put into ports along the African
  coast for fresh water, often having to do battle
  with local native tribes in the process.

• Dangerous unpredictable currents and weather
  conditions around the Cape of Good Hope.

• Pirates!

It was a long and dangerous voyage if you made
the trip successfully, you got rich, if not, you
lost it all!
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Toscanelli
The idea of sailing west out into the Atlantic
Ocean to reach India started with the Florentine
astronomer Toscanelli.
Toscanelli attempted to calculate the distance
from Portugal to India, via the western
direction. His calculations placed India about
where Central America is located.
He sent his calculations to the King of Portugal
suggesting an expedition to confirm his figures.
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Christopher Columbus
Columbus sent for a copy of Toscanellis
calculations, and based his voyage in part on
these inaccurate calculations. (If Toscanellis
math had been better, Columbus would have
realized that no ship in that time could have
made that long of a voyage over open sea.)
In 1492 Columbus set sail and made landfall at
about the area where Toscanellis calculations
put India. So Columbus called the natives
Indians when he landed in Central America.
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Riches in the New World
When Columbus discovered that he had not, in
fact, reached India, it was not a great
disappointment, because they heard stories of
natives to the south that had cities of gold and
silver.
Once the word of such riches to be plundered
spread around Europe, many captains set sail to
claim these new lands for their respective
sponsors.
The Portuguese and the Spanish claimed most of
the gold and the silver, but were pretty hard on
the locals in the process.
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Riches in the New World
Once looted, the gold and silver had to be
transported back to Spain.
To make the return voyage, they had to sail up
through the Caribbean past pirates, and up the
American coast to Virginia before using the trade
winds and the Gulf Stream to return to Spain.
Often these treasure ships fell prey to
hurricanes along the Florida coast, some of which
are only now being discovered and their rich
treasure brought to the surface.
The Wreck of the Atocha by Yeorgos N.
Lampathakis
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European Discovery of the Pacific
In 1513, Vasco Nuñez de Balboa  the Spanish
explorer and conquistador, crossed the isthmus of
Panama to become the first European to explore
the eastern Pacific shore.
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The Exploration of the Pacific
When word of Balboas discovery reached Europe,
Ferdinand Magellan left Spain on an expedition
that would take his ship around the world, the
first circumnavigation of the globe.
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Scientific Exploration Begins
The voyages of the Age of Discovery were for
trade or commercial reasons.
By the 1700s, all the gold had been claimed and
the new continents divided up among the European
countries that made the first claims.
From this point on, ocean voyages were more for
scientific knowledge than commercial gain.
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The Voyages of Captain James Cook
This new era can be said to have started with the
voyages of Captain James Cook.
Cooks first voyage was to transport a group of
astronomers to the island of Tahiti.
He made the first accurate charts of the coasts
of Australia, New Zealand, and some of the island
chains in that region.
On two later voyages, Cook discovered South
Georgia and South Sandwich Islands, and on his
last voyage, the Hawaiian Islands.
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Navigational Technology Advances
To fix his latitude, a navigator would use a
device known as a sextant to measure the angle
between the horizon and a nighttime star (such as
Polaris, the North Star).
However, to determine a ships longitude, it is
necessary to measure time.
Part of Cooks success on these last two voyages
can be attributed to improved navigation methods
using a chronometer (or clock).
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Determining Longitude
Suppose you were on a ship in the middle of the
Pacific, and you knew by your watch when it was
noon in Greenwich, England, located on the prime
meridian (longitude 0º).
You could then measure the elapsed time T for the
sun to reach its zenith (noontime) at your
location.
Because the earth rotates at a uniform rate of
360º every 24 hours, you could calculate your
longitude ? by solving the proportion
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Example
Suppose as the navigator on board a ship located
on the equator. To identify your longitude, you
observe that when the sun is at its highest point
in the sky, the ships clock indicates that it is
10 pm in Greenwich, England. Find your longitude
?. What ocean are you in?
T 10 hours have elapsed since the sun passed
over the prime meridian.
Solve for ?
A location of 0º latitude and 150º longitude
means that you are in the Pacific Ocean.
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The Longitude Problem
As of the 18th century, a chronometer that could
keep accurate time aboard a rocking ship over a
long voyage had not yet been invented.
To deal with this problem, the British Royal
Society posted a huge reward of 20,000
(equivalent to over 1 million today!) for the
first person to invent an accurate ships clock.
John Harrison, a working-class carpenter with
little formal education, eventually claimed the
prize.
Harrisons clock was accurate to three or four
minutes by the end of a sixth month voyage. Using
this more precise clock, Cook was able to make
accurate charts of the entire Pacific Ocean.
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Determining Speed
In addition to the chronometer, mariners by then
had developed a simple device, called a
Dutchmans Log (a stick attached to the end of a
string with a sequence of knots) to measure the
speed of a ship at sea.
At regular periods during a voyage, the navigator
would drop the stick from the stern. As the ship
sailed away, the string would run out over the
navigators hand. He would then count number of
knots that passed his hand in a measured time
period, and this was recorded as the speed of the
vessel.
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Origin of Nautical Terms
Later the term knot was defined as a speed of one
nautical mile per hour. (A nautical mile,
corresponding to the arc length of one minute of
latitude, is 1852 meters or about 1.15 statute
miles. Thus a ship sailing at 10 knots would be
moving at a rate of 11.5 mph.)
When the navigator went to record the speed from
the Dutchmans Log, the book he wrote the speed
into became known as the log. Even today,
captains of large sailing vessels keep a diary or
journal of the voyage called the ships log or
the log book.
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American Contributions
Following the American Revolutionary War,
Benjamin Franklin was the deputy postmaster
general for the American colonies.
He noted that ships using a northerly route took
two weeks longer to cross the Atlantic from east
to west.
In conversations with ships captains, Franklin
learned of a large, powerful current that went
north along the Atlantic coast of the colonies
and then east across the North Atlantic.
The ships using the northerly route were sailing
against this current, thereby making the voyage
longer.
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The Gulf Stream
The current was named the Gulf Stream because
it was thought that it originated in the Gulf of
Mexico.
In 1777, Benjamin Franklin was the first to
publish a chart of the Gulf Stream.
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