Chapter 2: Marine Exploration

Sailing and Buoyancy

No one knows when people first went to sea. Most archeological evidence points to a very early begining in the relationship between people and the sea. To effectively travel by water one needs a boat that floats and that can be moved by human power (ie. rowing or paddling) or wind power (ie. sailing.) (image source: unknown)

The properties that govern whether a solid object will float in the water are easy to understand and were first put into words by Archemedies over two thosand years ago. An object will float if it can displace a mass of water equal to or greater than the mass of the water it displaces. When you get into a bathtub the water goes up because of displacement. Your mass is pushing water up and to the side. In the same way an aircraft carrier made of steel and cement, weighting several thousands of tons can float as long as it displaces a greater mass of water. To learn more click on buoyancy.

Sailing, at a basic level is simple. If you are out in a canoe while the wind is blowing, and you open up and umbrella, the force of the wind will speed you along - you are sailing. However, if you don't just want to be blown around by the wind, but want to go a specific direction - sailing can become much more challenging. Here the technique you use and the size and shapes of the sails you use become very important. Click here to try out the sailing game, and learn a little bit more about sailing a race course.

Early Sailors

The Polynesians - They managed to populate nearly every island in the Pacific. They made use of large outrigger canoes, stick charts (maps), knowledge of bird and fish migration patterns, wave patterns, and stars to navigate. For more information about navigation of outrigger canoe's see: The history of Polynesian Exploration and Polynesian Navigation (image from Wikipedia Commons)

The Greeks, Phoenicians, and Egyptians - Mediterranean peoples developing large vessels (both rowing and sailing) for military and trading purposes on the Mediterranean Sea. Their vessels made use of a square sail that could not sail against the wind. For more information see: Ancient Greeks - Ships and Sea (BBC)

The Vikings - The invention of the long boat, and a temporally favorable climate, allowed the vikings of Norway and Sweden to explore and settle Greenland, Iceland, and Newfoundland. The long boat was noted for its speed and flexibility. The combination of new technology and warm climates allowed them to raid many villages in the British Isles. Click to read more about The Secrets of Viking Ships (image from Wikipedia Commons)

Europeans The Europeans were late to the game of marine exploration, but when they arrived they did so with missionary zeal and lust for gold. Europeans were quick to catch up and eventually came to dominate marine exploration and oceanic trade. They built bigger, wider, and much heavier three masted sailing vessels capable of traveling great distances. Magellan completed the first circumnavigation of the planet with such boats. For lots more pictures and history check out the History of European Sailing Ships.

Early Navigational Technology

The Polynesian Stick Chart - The idea of sticks and rocks tied together to serve as a map may seem childish, but these Polynesian stick charts were accurate and sophisticated maps that revealed current patterns in relationships to islands and allowed ancient navigators to travel thousands of miles between islands. (image from: Wikipedia Commons)

The Chinese Lodestone (The first compass) - The Chinese were the first to balance a small sliver of lodestone in a bowl of water or oil and use it to point north (a very simple compass). This technology, developed in the first century AD would eventually evolved into the modern compass.

Lead Line - The first documented use of a lead line to measure depth was by the Ancient Egyptians. The lead line was a simple device made of a lead weight on the end of a long rope. The rope was marked at intervals with strips of cloth or leather to show the depth. Early explorers modified the lead line so that it could be used to take sediments samples. The lead weight was shaped like an upside down bowl – it was filled with tallow. When the weight hit the sea floor the sediment stuck to the tallow. Experienced sailors used this information in shallow coastal waters to help them determine where they were. The fathom - comes from the old English faethm, meaning "out stretched arms" -estimated to average 6 feet from fingertip to fingertip. The fathom became the standard measure for gauging the depth of the ocean. 1 fathom = 6 feet = 1.83 meters

Chip Log - Early mariners in Europe used a device called a chip log for measuring their speed through the water. The chip log was made of a triangular piece of wood, weighted on one side and attached to a line with marked (knots) lengths. When thrown from the stern of a vessel the line was allowed to run out for a specified time. The number of knots that had come off the reel determined the vessel's speed. Today a ship's speed is still referred to in knots. 1 knot = 1 nautical mile per hour = approximately 50 cm per second, 1 nautical mile = 1º of latitude at the equator = 1.853 km. H4 - John Harrison's masterpeice

European Technology

Henry the Navigator - Prince Henry of Portugal created what was perhaps the first institution (or school) dedicated towards the science of sail, click to learn more about the early European navigation techniques that were taught at his school.

The Sextant - The sextant was developed in several stages in Europe. It allowed mariners to identify Latitude by sighting the angle of a celestial body (normally the north star) relative to the vessel they were sailing on. For more background of its history and lots of pictures see: History of the Sextant

The Marine Clock and the Longitude Challenge - Given a little patch of clear sky latitude was not difficult to measure, but the lack of any way to measure longitude cost European nations dearly. Ships frequently ran aground when they did not realize how far they were from dangerous coastlines or reefs. In 1714, England's Board of Longitude offered a huge reward to anyone whose method of measuring longitude could be proven successful. The Board favored a solution that computed longitude using the difference in the position of the moon, sun and stars from one location to another. The Board did not believe that a clock could be built that would accurately keep time at sea. The most accurate clocks at this time were pendulum clocks which do not work well at sea because of the movement of the boat. However, in 1735 John Harrison, a self-taught English clock maker, invented a watch that was not affected by changes in temperature or movement. Harrison’s watch utilized a counterbalanced mechanism controlled by springs, which ensured that any change in motion which affected one of the balances was compensated for by the other balance. Click to more about the story of John Harison and the Longitude Challenge, or to play the Longitude Game yourself. (Image from Wikipedia Commons.)

From Exploration to Science

The Beagle - Leaving Plymouth in 1831, this British ship carried Charles Darwin around the world for four years. Their work consisted of drawing maps, making observations, and collecting plants and animals. To see some of what Darwin wrote about and saw on that voyage go to link for an interactive version of Darwin's Beagle Diary

The H.M.S. Challenger - On December 21 1872, it began its four year, 127,000 km journey around the world. The goal of the expedition was to gather as many observations of oceanic phenomena as possible. In addition, the cruise was to determine if there was life in the deep oceans. While aboard the Challenger, scientists took readings on salinity, temperature and density, which contributed to the rapidly growing understanding of physical oceanography. Information about currents, sediment, and meteorology was also collected. Near the Philippines, it was proven that life did exist in the deep when samples were taken from depths of over 8000 meters. All the data were consolidated into a fifty volume set, entitled the Challenger Report, which set the scene for future marine research and is still consulted today (eg. the global seabed data base developed here in the department by Chris Jenkins includes the sediment descriptions done by the Challenger scientists- in some locations these are still the only descriptions available). Click for more information...

Questions to Research