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B.C. - Archaeologists have discovered that the Phoenicians used coastal and deep-water routes for both trade and voyages of discovery. Coastal sailors only sailed during the day, from one village to another, always keeping land in sight. Deep-water sailors took routes farther away from the coastline but kept sight of land. When sailing at night, sailors kept their ship in the right direction by observing constellations and the North Star, or what the ancient world called the "Phoenician Star."

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More than 1300 years ago, Polynesian explorers set out from Havai’I (now Raiatea, in the Society islands) in great double-hulled canoes across the vast unknown expanse of the North Pacific Ocean. By chance, they discovered and subsequently colonized, the Hawaiian Islands. A long canoe voyage across the uncharted ocean must have required an exceptional degree of navigational skill.

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Columbus departed Palos, Spain, with three ships on August 3, 1492. The Nina, a lateen-rigged caravel, the Pinta, a square-rigged caravel and the Santa Maria, a nao, was Columbus' flagship. He first landed in the Canary Islands, and then the Bahamas on October 28. He sailed near Cuba and Hispaniola and returned to Spain on March 15, 1493.

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Prince Henry the Navigator of Portugal recognized the oceans’ importance to trade and commerce and he established a center of learning for the marine sciences. You could think of it as the first oceanographic institution. Mariners came to the center in Sagres, Portugal, to learn about the oceans and currents and how to make maps. These early maps provided the basis for important expeditions.

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The people who lived around the Mediterranean Sea began exploring this nearly landlocked sea several thousand years ago. Sailors from Egypt, Phoenicia and Crete mapped the regional coastlines to establish some of the earliest trading routes. Early Mediterranean civilizations, including the Greeks, have passed down many myths that include gods and goddesses who ruled over nature, such as Poseiden with his triton. Many Mediterranean legends, such as Jason and the Argonauts, also involved adventures on large and dangerous seas.

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About 2,900 years ago, the Greeks began to venture outside the Mediterranean, past the Straits of Gibraltar at the western end of the Mediterranean Sea. This narrow channel separates Europe from Africa, and the Mediterranean from the Atlantic Ocean. Just outside of the Straits of Gibraltar, early Greek sailors noticed a strong current running from north to south. Because the sailors had only seen currents in rivers, they thought this great body of water on the other side of the Straits was a very big river. The Greek word for river was okeano, which is the root of our word for ocean.

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In 1728, John Harrison, a British cabinetmaker and inventor, started working on an important instrument to aid seafarers navigating across large areas of ocean, far away from land or coastlines. At the time, pendulum clocks kept time. Obviously, these clocks did not work well on a ship on the rolling ocean! In 1736, after years of work, Harrison invented a clock that used a spring instead of a pendulum. It was the first marine chronometer, an instrument that could give accurate time on a rolling ship.

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With the marine chronometer,, sailors could figure out how far east or west they had gone from 0° Longitude, or the prime meridian, and what longitude they were sailing past. By 1761, Harrison had built four clocks, each better than the one before.

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Benjamin Franklin (1706-1790) served as the United States colonial deputy postmaster general from 1753 to 1774. He found that British merchant ships arriving in the colonies from England took many days to weeks longer to make the voyage than American vessels. Besides being a famous statesman and diplomat, Benjamin Franklin was a well-known American scientist. He contributed to oceanography in the mid- to late 1700s by making and compiling good observations of ocean currents off the US East Coast. He was particularly interested in the Gulf Stream, a fast-moving current of warm surface water that sweeps up from Florida

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One of the most famous voyages of discovery of this time began in 1768 when the HMS Endeavour left Portsmouth, England, under the command of Captain James Cook. Over 10 years Cook led three world-encircling expeditions and mapped many countries, including Australia, New Zealand and the Hawaiian Islands. He was an expert seaman, navigator and scientist who made keen observations wherever he went.

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Charles Darwin’s scientific career began humbly. In 1831, and in the teeth of a gale, the HMS Beagle, a British warship, left Devonport, England, for an expedition to map the South American coastline and to carry out chronometer surveys all over the globe. Darwin was also fortunate that the Beagle took him to the Galapagos Islands, where he observed various animals and birds that had evolved in an isolated environment. His observations led him to his famous theory of natural selection. According to Darwin’s theory, variations within species occur randomly and the survival or extinction of an organism is determined by its ability to adapt to its environment.

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Maury conducted the first systematic study of the ocean's surface currents and winds. He compiled information on currents and winds from the thousands of logbooks of sailors' observations stored at the U.S. Navy's Depot of Charts & Instruments and published the first charts of the North Atlantic in 1847. He produced the first reliable wind and current charts of the ocean.

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Modern oceanography began with the Challenger Expedition between 1872 and 1876. It was the first expedition organized specifically to gather data on a wide range of ocean features, including ocean temperatures seawater chemistry, currents, marine life, and the geology of the seafloor. For the expedition, HMS Challenger, a British Navy corvette (a small warship) was converted into the first dedicated oceanographic ship with its own laboratories, microscopes and other scientific equipment onboard.

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Among the Challenger Expedition’s discoveries was one of the deepest parts of the ocean—the Marianas Trench in the western Pacific, where the seafloor is 26,850 feet, or more than 4 miles deep (8,200 meters). The deepest place in all the oceans is near where the Challenger took its sounding.

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In 1855, Matthew Maury published “The Physical Geography of the Sea,” which is now credited as “the first textbook of modern oceanography.” The devices on the right hand side of the page are sounding instruments to measure the depth of the ocean.

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American naturalist Louis F. de Pourtales conducts dredging operations from the Coast Survey Steamers Corwin and Bibb off the southern coast of Florida. During the operation, he finds prolific life extending below 300 fathoms (1,800 feet or 550 meters).

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The French Navy launches the submersible Gymnote. It is the first electrically powered and fully functional military submarine. The steel-hulled craft is powered by a 204-cell battery. It completes over 2,000 successful dives before being scrapped for its limited range.

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In the mid- to late-1800s, Matthew Fontaine Maury became head of the US Navy’s Department of Charts and Instruments—only to discover that the Navy had very few charts of the oceans! But it did have a big storeroom of dusty logbooks from Navy ships. In these logbooks, sea captains traveling the North Atlantic had recorded their daily locations, as well the speeds and directions of winds and currents. Maury realized the books contained a gold mine of information. By compiling records from many ships, he saw patterns. He made charts of ocean currents and winds that helped captains plot the best sea lanes for their voyages. He added more details to these charts by asking merchant captains to make more observations and send them to him.

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The Challanger expedition was led by British naturalist John Murray and Scottish naturalist Charles Wyville Thompson. Thompson had previously dredged some curious creatures from the ocean depths in the North Atlantic and the Mediterranean Sea, and these discoveries persuaded the British government to launch a worldwide expedition to explore the ocean depths. The Challenger Expedition left Portsmouth, England, just before Christmas in 1872.

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The Kon-Tiki was constructed from wooden balsa logs in an attempt to duplicate Peruvian rafts described by early Spanish explorers in the sixteenth century. The native rafts were equipped with sails and an unusual steering system that made them effective in carrying large

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Englishman William H. James designs a self-contained underwater breathing apparatus, or scuba. In James' design, the diver wears a helmet and carries a supply of compressed air in a cast-iron belt fastened around the waist. This device allows the diver to remain underwater for up to an hour.

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Henry Stommel (1920 – 1992)

was driven to understand the forces that cause narrow, fast, Western Boundary currents to strengthen. He advanced theories about global ocean circulation patterns, in particular, the behavior of the Gulf Stream. His ideas helped form the basis of physical oceanography today. He is recognized as one of the most influential and productive oceanographers of his time

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Thor Heyerdahl (1950) described these events vividly as he and five companions crossed 7,700 kilometers of the equatorial Pacific on Kon-Tiki in 1948. Detractors predicted that they would be lost at sea. It is of interest to investigate modern, in situ, and satellite ocean measurements to determine why and how the voyage succeeded.

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The Coastal Zone Color Scanner Experiment (CZCS), launched aboard NIMBUS-7 in October 1978, was the first instrument devoted to the measurement of ocean color and flown on a spacecraft. Although other instruments flown on other spacecraft had sensed ocean color, their spectral bands, spatial resolution and dynamic range were optimized for land or meteorological use and had limited sensitivity in this area, whereas in CZCS, every parameter was optimized for use over water to the exclusion of any other type of sensing

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NASA's Quick Scatterometer (QuikSCAT) was lofted into space at 7:15 p.m. Pacific Daylight Time on Saturday (6/19/99) atop a U.S. Air Force Titan II launch vehicle from Space Launch Complex 4 West at California's Vandenberg Air Force Base. The satellite was launched in a south-southwesterly direction, soaring over the Pacific Ocean at sunset as it ascended into space to achieve an initial elliptical orbit with a maximum altitude of about 800 kilometers (500 miles) above Earth's surface.

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Jason-1 is an oceanography mission to monitor global ocean circulation, study the ties between the oceans and atmosphere, improve global climate forecasts and predictions, and monitor events such as El Niño conditions and ocean eddies.

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For oceanographers, sonar provided a much easier way to measure the ocean depths accurately. On the 1872-76 Challenger Expedition, for example, crew members threw overboard a 200-pound weight attached to miles of hemp rope. They waited until it hit bottom, measured the rope length, and then had to haul it back on board-a process that took hours for one measurement!

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In 1915, Wegener proposed his continental drift theory. He said that the continents floated atop the mantle-a heavier, denser layer of rocks deep within the earth. Wegener predicted that heat rising within the hot mantle created currents of partially melted rocks that could move the continents around the earth’s surface.

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In the 1950s and 1960s, marine geologists such as Bruce Heezen, Marie Tharp, and Henry Menard used data from echo sounders to map ocean ridges in the North Atlantic and the Pacific. They noticed first that these ridges stretched on for thousands of kilometers in long, continuous mountain chains that wound around the Earth’s surface, almost like the stitches on a baseball.

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The scientists also observed that the crest of the ridges had a topography that closely resembled volcanic rift zones on land. At their crests, they had V-shaped central valleys with steep faults on either side. This evidence led early marine geologists to deduce that the mid-ocean ridges were formed by seafloor volcanoes.

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When these volcanoes erupted, they spewed out lava that cooled and solidified to become new seafloor. It was soon discovered that when this lava cooled, magnetic particles within it aligned with Earth’s magnetic field. After World War II, when magnetometers began to be used to survey the seafloor’s magnetic properties, scientists were surprised to learn that Earth’s magnetic field had flip-flopped many times over its history, with the north and south poles exchanging places! So depending on when seafloor rocks were formed, their particles are aligned in either one direction or the other, and they are said to have either positive or negative magnetic anomalies.

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In 1965, a Canadian geophysicist, J. Tuzo Wilson, combined the continental drift and seafloor spreading hypotheses to propose the theory of plate tectonics. Tuzo said that Earth’s crust, or lithosphere, was divided into large, rigid pieces called plates. These plates “float” atop an underlying rock layer called the asthenosphere. In the asthenosphere, rocks are under such tremendous heat and pressure that they behave like a viscous liquid (like very thick honey).

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In 1968, an international group of oceanographic institutions and the U.S. National Science Foundation created a program of ocean drilling. Its initial goal was to test Tuzo Wilson's hypothesis of plate tectonics.

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The cores provided evidence to confirm seafloor spreading and plate tectonics, but they also revealed much more. The long sections of sediments that accumulated layer by layer on the seafloor also provided a record of how the Earth's climate has changed during its history. The subseafloor sediments and rock also contained a treasure trove of clues that reveal the Earth's structure and evolution. Many of these clues cannot be found in rocks on land, because they are eroded away. But they are well-preserved below the seafloor.

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But less than 100 years ago, a German scientist named Alfred Wegener took notice of some interesting findings. Similar plant and animal fossils were found in both Africa and South America and on other continents separated by oceans. Similar rock formations were also found on distant continents. This suggested that the formations were once whole and later divided.

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The military also developed other tools that also proved useful to oceanographers, such as the magnetometer, which measures magnetic fields. The Navy uses it to detect the large metal hulls of submarines. Oceanographers use it to learn about magnetic properties of seafloor rocks. As it turned out, these properties provided key clues that completely changed our thinking about how our planet works.

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The U.S. submarine Seawolf (SSN 21) puts to sea in the Narragansett Bay operating area for her first at-sea trial operations. U.S. Navy photo courtesy of General Dynamics.

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Most of the major discoveries in oceanography have occurred only within the last 50 years. We have found that while rocks and sediments on land are usually wiped away by weather and erosion, rocks and sediments on the seafloor are a well-preserved archive of information that allows us to unravel Earth’s geological processes and history.

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We have discovered hydrothermal vents on mid-ocean ridge crests, which support previously unimagined ecosystems and exotic communities of life. Heat from the Earth’s interior, rather than the sun, supports these life forms, which may hold clues to the origin of life on Earth and possibly to life on other planetary bodies.

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Oceanographers will use different types of remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) that can “fly” in the oceans or along the seafloor, collecting measurements. The data can be downloaded when the AUVs surface, or when they dock at an underwater docking site and download data there. Oceanographers are also developing instrumented buoys moored thousands of miles from shore, and free-floating drifting instruments that can transmit data to scientists in their laboratories using satellites and the Internet.