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The bound captive stepping off a board over the sea is the classic pirate image, yet it virtually never happened during the Golden Age of Piracy, from the late 1600s to about 1730. The earliest documented account comes from a 1763 report in the Public Advertiser describing crews near Guadeloupe and the Grenadines who made captured sailors walk into the sea on a plank fixed for that purpose, with one strong swimmer surviving. In 1788 Francis Grose's Dictionary of the Vulgar Tongue defined walking the plank as a method mutineers used against loyal officers, blindfolded so the killers could claim the victim died by his own steps and avoid a murder charge. The same year, surgeon's mate Mr. Claxton told a House of Commons committee that the captain of the slave ship Garland planned to make enslaved people walk the plank if delayed ten more days, and Thomas Clarkson recorded a similar 1779 threat.

Verified pirate use came a century after the Golden Age, in the Caribbean of the 1820s. In July 1822 the Spanish schooner Emanuel captured the British sloop Blessing and forced Captain William Smith off the plank. In February 1829 the Times reported pirates on the schooner President shooting the commander of the Redpole and making the survivors walk. Later in 1829 pirates in the Leeward Passage made the crew of a Dutch brig walk the plank with cannonballs tied to their feet. Fiction did the rest: Charles Johnson's 1724 General History of the Pirates, Charles Ellms's 1837 Pirate's Own Book with its Walking the Death Plank illustration, Robert Louis Stevenson's Treasure Island, and J.M. Barrie's Captain Hook fixed the plank in popular memory.

• A supposed Baltic plank pirate, John Derdrake, is suspected by historians to be fictional.
• Mutineer George Wood's reported 1769 Newgate confession to sending officers down the plank remains unverified.
• Johnson described Roman captives offered a ladder into the sea and freedom if they could swim.
• An 1872 novel had pirate Dominique You confess that Theodosia Burr Alston walked the plank with a smile and a wave.
• The ninja's black outfit came from Japanese theater stagehands, a parallel case of costume replacing history.

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A catamaran is simply two parallel hulls of equal size, and that wide stance gives it form stability without the heavy lead keel a monohull needs, so it sits light and shallow in the water. The design was pioneered by Austronesian peoples, and it carried them across the Pacific and Indian Oceans as far as Madagascar. Anthropologists of the 1930s and 1940s assumed catamarans evolved from outrigger canoes, but later researchers showed the reverse: two logs lashed into a raft became twin carved hulls, then asymmetric double canoes, then the single outrigger, then the double outrigger or trimaran. Far Pacific sailors kept catamarans and single outriggers and learned to shunt, moving the sail to the other end so the outrigger always faced the wind. The name itself is a mix up, from the Tamil kattumaram, logs bound together, a single hulled raft of three to seven trunks.

In Europe, William Petty's twin hulled merchant boat of 1662 was mocked and failed. Then in 1876 Nathaniel Herreshoff's Amaryllis flew past the deep keeled yachts at the New York Yacht Club's centennial regatta, and the club banned catamarans from regular classes, a ban that held back Western development into the 1970s. Outsiders kept experimenting until Hobie Alter's beach cats, with over 100,000 Hobie 16s built, brought them to the public. The episode explains why narrow hulls dodge the bow wave speed limit and generate apparent wind for rigid wing sails, why catamarans resist capsizing up to seven times better than monohulls of the same width, and why they lose badly to monohulls at hauling bulk cargo.

• Leonardo Torres Quevedo patented a flexible twin hulled steel vessel in 1916 to absorb wave torque.
• Eric de Bisschop sailed a Polynesian style double canoe from Hawaii to France in the 1930s.
• The Prout brothers used a mast aft rig so the jib lifted the bows and prevented pitchpoling.
• Frederick G. Creed patented the SWATH design, with submerged torpedo hulls on thin struts, in 1938.
• Steve Fossett's 125 foot PlayStation hit 50 knots, and the solar powered Tûranor PlanetSolar circled the globe.

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Thor Heyerdahl, the Norwegian adventurer, zoologist, and ethnographer who lived from 1914 to 2002, nearly drowned twice as a boy in Larvik and grew up terrified of the water. His mother passed on her fascination with Charles Darwin, and he kept a homemade zoological museum with a live viper in his bedroom. In 1936, the day after marrying Liv Coucheron-Torp, he left for Fatu Hiva in the Marquesas under a cover story of studying animal migration, hoping to live off the grid. Disease drove them home after about a year, but the east winds and currents battering the island gave him his theory: that South Americans drifted west to settle Polynesia. Rejected by academics, he built the Kon-Tiki from green balsa and hemp in Peru in 1947 and drifted 101 days and about 5,000 miles before wrecking on a reef in the Tuamotus. His book reached 70 languages and his film won an Academy Award in 1951.

Critics called his Tiki people idea, with its bearded, light skinned sun worshippers and supposedly inferior Asian migrants, hyperdiffusionism, and in 1976 the Polynesian Voyaging Society's Hokulea sailed from Hawaii to Tahiti against the wind by traditional wayfinding, while DNA later confirmed an Island Southeast Asian origin. Heyerdahl turned to the Atlantic with papyrus boats: Ra broke apart in 1969 after missing a tension rope seen in ancient drawings, and Ra II, built with Aymara craftsmen from Lake Titicaca, reached Barbados in 1970 with a crew from the US, the USSR, Egypt, Mexico, and Italy. In 1978 he burned the seaworthy Tigris in Djibouti to protest war and the arms trade. His later theories grew stranger, and he died in 2002 after refusing food and medication, receiving a Norwegian state funeral.

• A wealthy Oslo wine merchant's private library of Pacific books fueled his early Polynesia obsession.
• Locals in Tahiti persuaded the unprepared couple to take at least a machete and a cooking pot to Fatu Hiva.
• The Ra voyages collected some of the earliest data on marine oil pollution for the United Nations.
• Excavations of the Güímar pyramids in Tenerife found 19th century pottery and an 1848 seal, showing they were farm terraces.
• His Search for Odin linked the Aesir to the Russian city of Azov and the god Tyr to Turkey through sound alike words.

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A 1960 US Air Force airframe maintenance manual sends mechanics to Waterline 50 to repair a supersonic jet. The episode explains why. A ship's hull is all compound curves, so naval architects draw waterlines, horizontal slices parallel to the water's surface, like contour lines on an inverted topographic map, letting builders read the hull's exact shape at every depth on a two dimensional lines plan. One waterline is also law: the load line or Plimsoll line marks how deep a ship may legally be loaded, with separate marks for tropical fresh, fresh, summer, and winter North Atlantic water, since warm fresh water is less dense than cold salt water and a loaded ship rides lower in it.

Waterline length also caps the speed of displacement hulls. A ship rides between its bow wave and stern wave, and as it speeds up the stern wave slides aft until the stern drops and the bow climbs its own wave. Longer waterlines raise that hull speed, and racing sailboats are shaped so that heeling lengthens the waterline. Early aircraft makers hired shipbuilders, who brought lofting and waterlines with them.

• Lofting takes its name from the lofts above shipyards where lines were drawn full size on the floor.
• Archimedes' principle means a ship sinks until it displaces its own weight in water.
• Adding engine power to a displacement hull at hull speed mostly makes a bigger wave.
• Aircraft waterlines are measured in inches from a baseline designated waterline zero.
• When waterline zero sits at the nose cone tip, parts below it such as landing gear get negative waterline numbers.

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Stockton Rush co founded OceanGate in 2009 with shallow wreck dives off California and in the Gulf of Mexico, but he knew the Titanic was the name that would sell seats at up to $250,000 each. He called safety regulations a pure waste and opposed the Passenger Vessel Safety Act of 1993. Rather than a titanium sphere, the Titan was a 2.4 meter carbon fiber cylinder with titanium end caps, built to hold five, using carbon fiber he said came cheaply from Boeing past its shelf life, a claim Boeing disputes. Carbon fiber excels under tension but buckles under repeated compression, and Rush relied on a patented acoustic monitoring system to warn of cracking instead of seeking classification from bodies like Lloyd's Register.

In 2018 David Lochridge, OceanGate's director of marine operations, warned the system would give only milliseconds of warning and that the viewport was rated for a fraction of Titanic depth. Rush fired and sued him, and dismissed warnings from Will Kohnen of the Marine Technology Society and Rob McCallum. On June 18, 2023, Titan went silent at 3,341 meters after reporting two dropped weights, a routine step. Its debris lay 500 meters from the Titanic's bow.

• The original hull cracked and was rebuilt by 2021, and Rush reused titanium rings from the damaged hull against engineering advice.
• In 2022 a thruster was installed backward, and the pilot steered by holding the game controller sideways.
• A loud bang on a July 2022 ascent was later judged by the Coast Guard to be the hull delaminating.
• A Navy acoustic system built to track Cold War submarines picked up the implosion while the public search went on for days.
• Paul-Henri Nargeolet's family is suing OceanGate for $50 million for wrongful death.

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Commercial fishing is still the second most dangerous job in the US, and sailor superstitions grew as ways to feel in control of a sea that could kill at any moment. Older scholars dismissed them as childish folklore, but many hide practical sense. Red sky at night, sailor's delight works in the mid latitudes because weather moves west to east. Whistling was said to raise a gale, but officers also feared it as a mutineer's signal; only the cook could whistle, proving he was not eating the crew's food. Bananas give off ethylene gas that rots other stores. Killing an albatross brought doom, and in Norwegian tradition cormorants were the spirits of the drowned.

In the 19th century sailors bought ropes from Finnish wind merchants with three knots: the first for a breeze, the second for a strong wind, the third for a gale. Clergymen, redheads, and women were shunned as Jonahs, though Pliny the Elder claimed a naked woman could calm a storm. Friday was the unlucky day for sailing, and cruise lines still skip decks 13 and 17. Cats earned their place as ratcatchers, and a University of Leuven DNA study traced cats spread along shipping lanes by eighth century Viking traders.

• Polydactyl cats were prized for balance, and throwing a ship's cat overboard meant nine years of bad luck.
• A pig and a hen tattooed on the feet promised survival, since those animals floated away in their crates when ships sank.
• A baby's caul was sold to sailors as protection against drowning.
• Franklin D. Roosevelt wrote to Eleanor about his line crossing initiation aboard the USS Indianapolis.
• One theory holds that Davy Jones is a corruption of Devil Jonah, with Fiddler's Green as the sailors' paradise.

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The viral sea shanty craze got the history wrong: most of the songs, including The Wellerman, are not shanties, and 18th century pirates never sang them. A shanty was strictly a work song, sung without instruments in call and response, led by a shantyman who acted as a foreman timing the crew's effort. Leisure songs in the forecastle were forebitters. The Royal Navy banned singing at work, keeping time with fifes, fiddles, and the bosun's pipe and relying on huge crews. Shanties arose after the War of 1812, when fast packet and clipper ships on tight commercial schedules sailed with far smaller crews that had to coordinate every pull.

The structure came from African American work songs. At ports like Mobile Bay, a shanty mart, Black stevedores sang to time cotton screwing, jacking bales into ship holds, and white sailors working winters ashore picked up the form. Hauling shanties timed pulls on ropes, while heaving shanties kept a steady pace at capstans and pumps. Steam winches ended the tradition, and collectors such as Cecil Sharp and Stan Hugill cleaned up the lyrics and downplayed the African American roots.

• Long drag shanties built a pause for the crew to reset their grip before one synchronized pull on the final beat.
• Short drag shanties drove quick successive pulls for sudden sail adjustments in storms.
• Sailors spent their month's advance ashore, then worked off the dead horse unpaid for their first month at sea.
• When the debt cleared, crews hoisted a straw and canvas horse to a heaving shanty and cut it loose into the sea.
• An 1880s writer lamented that singing and steam are irreconcilable.

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Launched in 1797, the 44 gun frigate USS Constitution is the oldest commissioned naval vessel still afloat, though wooden warships of her day lasted perhaps 10 to 15 years. The Naval Act of 1794 funded six frigates to fight Barbary piracy, and Joshua Humphreys designed them long and narrow for speed but heavily gunned, with diagonal riders inside a 21 inch hull of southern live oak cut by enslaved workers on Georgia's Sea Islands. Her launch in Boston in September 1797 stalled twice as her keel sank into the clay. In 1803 Captain Edward Preble faced down a ship in the dark off Gibraltar that claimed to be the 84 gun HMS Donegal; it was the 32 gun HMS Maidstone, and his officers became Preble's Boys.

In July 1812 Captain Isaac Hull escaped five British warships in a dead calm by kedging for 57 hours and dumping 2,300 gallons of drinking water. A month later HMS Guerriere's shot bounced off her sides and a sailor cried that they were made of iron. She went on to beat HMS Java and to take the Cyane and Levant together. Oliver Wendell Holmes's poem Old Ironsides saved her from scrapping in the 1830s, and schoolchildren's pennies funded her 1920s restoration.

• Samuel Dewey sawed the head off an Andrew Jackson figurehead during a thunderstorm and delivered it to the Secretary of the Navy.
• Lieutenant John Lord found live oak cut in the 1850s still sitting in a pond at the Pensacola naval air station.
• A 1992 to 1995 restoration fixed a 13 inch hog using wood from trees downed by Hurricane Hugo.
• The Navy keeps a 25,000 acre Constitution Grove in Indiana to grow white oak for future repairs.
• In 2022 Commander Billie J. Farrell became the first woman to command the ship.

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Artemis II astronauts carry an emergency backup built on a design about 300 years old: the sextant. Isaac Newton sketched the theory in unpublished writings, and around 1731 John Hadley in England and Thomas Godfrey in America independently built instruments using double reflection. Older tools like the mariner's astrolabe and cross staff depended on a steady plumb line, useless on a pitching deck, but two mirrors let a navigator lay the sun or a star directly on the horizon so both images move together. Rotating the index mirror doubles the reflected angle, so a 60 degree arc reads 120 degrees. The episode walks through a noon sun sight: holding the handle, not the arc, lowering the sun to the horizon, and swinging the sextant to find the bottom of the arc.

A sight also needs exact time and the height of eye to correct for dip. Brass and aluminum trade stability against fatigue, heat warps both, and a pool of mercury or a bubble can stand in for a hidden horizon. Carlos Viegas Gago Coutinho adapted the instrument for aircraft around 1922, and later bubble sextants used clockwork averagers to cancel turbulence. Neil Armstrong pushed for a sextant built into the Apollo capsules.

• A skilled navigator can fix a position to within a tenth to a quarter of a nautical mile.
• Star sights must be taken in nautical twilight, while stars show but the horizon is still visible.
• The four adjustable errors, perpendicularity, side, collimation, and index, must be corrected in that order.
• When Gemini 12's rendezvous radar failed, Buzz Aldrin worked out the rendezvous with a handheld sextant, star charts, and a slide rule.
• Experiments on the International Space Station in 2018 showed a handheld sextant could guide an emergency return.

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On July 12, 1999, the United States sent its last commercial Morse message, repeating the 1844 words What hath God wrought, and in January 1997 the French Navy signed off with a call before its eternal silence. Yet the code never went quiet. Samuel Morse first planned to send only numbers keyed to heavy code books, but Alfred Vail counted the metal type in a Morristown, New Jersey print shop and gave the shortest codes to the most common letters, a variable length scheme that worked like data compression a century before computers. Operators soon ignored the paper tape and read the clicks by ear.

Vail's American Morse had odd gaps inside letters, so in 1848 Friedrich Clemens Gerke's Hamburg alphabet cleaned it up and became the basis of the 1865 international standard, though American railroad telegraphers kept the old code into the 1950s. Timing runs in ratios of one, three, and seven dits. Each operator's timing quirks form a fist that Allied intelligence used in World War II to track units. The code lives on in aviation beacons, amateur radio, and assistive switches such as sip and puff tubes.

• Theodore Roosevelt McElroy set the copying record of 75.2 words per minute in 1939.
• At high speed operators hear whole words as melodic shapes rather than single dots and dashes.
• A Morse signal fits in roughly 100 to 150 hertz, letting it punch through static that swamps voice.
• In 1966 prisoner of war Jeremiah Denton blinked the word torture in Morse during a North Vietnamese propaganda broadcast.
• In 2004 the International Telecommunication Union added the @ symbol so email addresses could be sent.