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Dead reckoning estimates where you are from a known starting point, called a fix, plus your speed, heading, and elapsed time: distance equals speed times time. The phrase is not short for deduced reckoning, a claim debunked by the record, since dead reckoning appears in 1613 and deduced reckoning not until 1931. The word dead likely refers to an object stationary in the water used as a baseline. The method's enemy is cumulative error, where each estimate builds on the last like a photocopy of a photocopy, worsened by drift from currents and wind. Nature and ancient engineers both mastered it: foraging ants use path integration to walk straight home after zigzagging, and China's south pointing chariot used differential gears to hold its pointer south without a magnetic compass.

Before the marine chronometer, dead reckoning was the only way to cross open ocean, as Christopher Columbus and John Cabot did. Crews marked heading and speed with pegs on a traverse board and measured speed with a chip log, counting knots in a rope against a sandglass, the origin of knots as a unit. Aviators faced wind as well: John Alcock and Arthur Brown in 1919 and Charles Lindbergh in 1927 relied on it, and pilots still learn the wind triangle for visual flight rules. Today cars fall back on wheel and steering sensors in tunnels, blended with GPS by a Kalman filter, and online games use the same math to predict other players' positions between server updates.

• The Oxford English Dictionary traces dead reckoning to 1613.
• A south pointing chariot turning left spins its right wheel faster, and gears counter-rotate the pointer to compensate.
• Flight instructors may cover a student's screens to force navigation by compass, clock, and math.
• Pedestrian dead reckoning in phones uses the accelerometer as a pedometer and the magnetometer as a compass.
• Games smooth corrections with projective velocity blending and cubic Bezier splines so players do not appear to teleport.

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When a quiet Georgia doctor and teacher named David Bush died in 1824, his neighbors learned he was really David Bushnell, who had tried to break the British blockade with a submarine. As a Yale student in 1775 he built a clockwork flintlock that could fire gunpowder inside a sealed keg underwater, then designed a way to deliver it unseen. With his brother Ezra Bushnell, carpenter Phineas Pratt, and New Haven clockmaker Isaac Doolittle, he built the Turtle: two oak shells bound with iron bands and coated in tar, about 10 feet long, 6 feet tall, and 3 feet wide. It had a foot valve and brass pump for ballast, hand cranked screws for propulsion, about 30 minutes of air, and dials lit by glowing foxfire fungus.

Winter cold stopped the foxfire glowing in November 1775, and even Benjamin Franklin could not suggest an alternative. George Washington, skeptical, provided funding, but Ezra fell ill, so volunteer Sergeant Ezra Lee had two weeks to learn the controls. On the night of September 7, 1776 Lee spent two hours cranking across New York Harbor to Admiral Richard Howe's flagship HMS Eagle off Governors Island, but his screw would not bite, probably striking an iron plate near the rudder rather than copper sheathing. At dawn, chased by a British boat, he released the 150 pound charge, which exploded in the East River. The Turtle sank with its transport sloop in the Hudson that October, and Bushnell's later floating mines led to the mocking Battle of the Kegs.

• The Turtle was the first submarine with a ballast tank and the first watercraft with a documented propeller.
• British naval historian Richard Compton-Hall has argued the attack may never have happened as described.
• Washington later wrote to Thomas Jefferson that the Turtle was an effort of genius requiring too many things to combine.
• A 2003 Massachusetts College of Art and Design replica was tested at the US Naval Academy.
• In 2007 artist Duke Riley surfaced his homemade sub, the Acorn, near the Queen Mary 2 and was cited for marine mischief.

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On an 18th century wooden warship the greatest danger was its own gunpowder. The bulk of it sat in a reinforced magazine deep below the waterline, while the cannons fired from the decks above, so someone had to run powder and pre-made cartridges up and down steep ladders all through a battle. That job fell mostly to powder monkeys, boy seamen aged 12 to 14, chosen for speed and small size. Between decks the clearance was sometimes well under five feet, and on the upper deck their height kept them hidden behind the gunwale from enemy sharpshooters firing down from the rigging. Some women and older men did the work too, but none of them held any official rank.

In Britain the Marine Society sent an estimated 500 to 600 boys a year to the Royal Navy in the mid 1790s, offering clothes, bedding, and basic education. Many came from desperate poverty, while others had fathers and grandfathers already at sea and joined for adventure and family tradition. The young United States Navy copied the Royal Navy's structure, and in the War of 1812 both fleets relied on boys to feed their guns. Afterward the US banned boys under 12 from its ships, but older boys kept serving as powder monkeys until the Spanish-American War. The Royal Navy term, coined in the 17th century, survives today for skilled blasters in mining and demolition.

• Pre-made canvas or paper cartridges sped up loading and cut down on loose powder spilling onto decks.
• A single stray spark reaching the main powder supply could destroy an entire ship.
• With no rank, powder monkeys got the lowest pay and the most dangerous assignments.
• The US Navy had no formal fleet until after 1776 and modeled itself directly on Britain's.
• Moving from black powder to modern explosives turned the job from child labor into skilled adult engineering.

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The first open sea lighthouse went up on the Eddystone Rocks off England in 1696, when Henry Winstanley anchored an octagonal wooden tower with 12 iron stanchions. The Great Storm of 1703 tore it away with Winstanley inside. In 1759 John Smeaton rebuilt it in granite shaped like an oak trunk, with a broad curving base that bleeds off wave energy, blocks dovetailed together and pinned with marble dowels, and hydraulic lime that cures underwater. Site dictated form elsewhere: tall towers on flat Cape May, a light at Point Loma set so high it sat in the fog and had to be replaced, and Alexander Mitchell's 1838 screw pile towers for sand and mud.

Light itself needed invention. Bonfires burned too fast and smoked, so Ami Argand's 1782 lamp used a hollow wick for clean combustion, Arthur Kitson's 1901 vaporized oil burner was six times brighter, and Gustaf Dalén made acetylene safe with a porous filler and built the sun valve, a blackened rod that switched the gas off at dawn. In 1823 Augustin Fresnel's ringed lens at Cordouan multiplied usable light fourfold, and rotating lenses gave each tower its own flash pattern. Later, the Soviet Union powered remote Arctic lights with strontium-90 generators, many lost when the state collapsed and stripped by scavengers who were exposed to radiation.

• Visible range follows a formula: 1.22 times the square root of the light's height gives distance in nautical miles.
• Souter Lighthouse in 1871 was the first designed specifically for electric light.
• A 1971 laser at Point Danger in Queensland was scrapped because its beam was too narrow to spot.
• Modern LEDs last up to 100,000 hours against about 1,000 for a filament bulb.
• Canada keeps human keepers at automated Machias Seal Island Lighthouse to assert its claim against the United States.

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In the late 1920s naturalist William Beebe, working from Nonsuch Island in Bermuda, wanted to study a column of ocean two miles deep, but diving helmets and submarines of the day could not do it. He announced plans for a cylindrical vessel, which engineer Otis Barton recognized as a death trap. Barton designed a sphere instead, paid for it, kept ownership, and insisted on joining every dive. The steel ball had an interior about four and three quarter feet across, weighed over two tons, and had three inch fused quartz windows and a 400 pound hatch bolted on from outside. Soda lime and calcium chloride scrubbed the air, stirred by palm leaf fans, while Gloria Hollister took notes over a phone line and John Tee-Van ran the deck.

The first casting in June 1929 was too heavy and had to be melted down. On June 6, 1930 the two men reached 803 feet, and Beebe watched red and yellow light vanish into blue. In 1932 a flooded unmanned test fired the hatch bolt 30 feet across the deck, yet on September 22, 1932 they dove to 2,200 feet during a live NBC radio broadcast, battered and seasick. National Geographic put up 10,000 dollars, and on August 15, 1934 they reached 3,028 feet with every foot of cable unspooled, surfacing after just five minutes. The record stood for 15 years, but critics doubted Beebe's new species without specimens, and Barton's resentment spilled into the film Titans of the Deep.

• An unmanned test brought the sphere up with its hose wrapped around the steel cable 45 times.
• Gloria Hollister set a women's depth record of 410 feet.
• Beebe met Auguste Piccard at the 1933 Chicago World's Fair, which pointed him to National Geographic funding.
• The bathysphere later sat under the Cyclone roller coaster at Coney Island until it was restored in 2005.
• Beebe's dives inspired Jacques Piccard's bathyscaphe and influenced the design of the submersible Alvin.

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In spring 2016 the UK's Natural Environment Research Council opened an online poll to name its new 200 million pound polar research ship, then being built in Birkenhead. BBC radio presenter James Hand suggested Boaty McBoatface, a nod to an owl named Hootie McOwlface, and it won 33 percent of the vote against 11 percent for second place, inspiring the term McBoatfacing. Science minister Jo Johnson named the ship RRS Sir David Attenborough instead, a name that placed fifth in the poll, and Duncan Wingham proposed the compromise: give the winning name to one of the yellow submersibles carried aboard.

That submersible is an Autosub Long Range vehicle run by the National Oceanography Centre in Southampton: about 700 kilograms, 3.6 meters long, rated to 6,000 meters, with a range of at least 2,500 kilometers and no tether, running preprogrammed missions for months. On its April 2017 maiden mission, DynOPO, launched from the RRS James Clark Ross, it traveled 180 kilometers through the Orkney Passage at depths up to 4,000 meters. Its data showed that stronger Southern Ocean winds drive internal waves that break over undersea ridges and mix cold bottom water with warmer water above, a sea level rise mechanism missing from climate models, published in the Proceedings of the National Academy of Sciences.

• Later in 2017 it tested chemical sensors in the North Sea to detect leaks from future carbon storage sites.
• In early 2018 it spent 51 hours under Antarctic ice, 20 of them beneath a 550 meter thick ice shelf.
• In August 2024 it made a 55 day, 2,000 kilometer voyage from Iceland to Scotland studying the ocean carbon pump.
• Its missions feed the UK Polar Explorer program for primary and secondary schools.
• In December 2017 Boaty McBoatface appeared as a category on Jeopardy.

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The oldest continuous trophy in international sport is a bottomless sterling silver ewer made by Garrard & Co. in London in 1848. Henry William Paget, first Marquess of Anglesey, bought it and gave it to the Royal Yacht Squadron as the prize for its 1851 race around the Isle of Wight, where the New York Yacht Club schooner America beat 15 British yachts as Queen Victoria watched. Valued at 100 pounds, it was engraved with an error, then renamed for the winning schooner, and sailors still call it the Old Mug. In 1857 the surviving owners gave it to the New York Yacht Club under a Deed of Gift making it a perpetual challenge cup between clubs of foreign countries.

The New York Yacht Club defended the Cup 24 times from 1851 to 1983, the longest winning streak in sport, helped by rules that forced challengers to sail across an ocean to the start. In 1983 at Newport, Alan Bond's Royal Perth Yacht Club broke it with Australia II, and the 1987 defense transformed Fremantle. Because the Deed is a charitable trust overseen by the New York Supreme Court, disputes go to court, including a 1988 ruling that a catamaran could legally meet a monohull challenge. Today's foiling AC75s fly on hydrofoils with rigid wing sails. In 2013 in San Francisco, Oracle Team USA overcame a cheating penalty and an 8 to 1 deficit to beat Emirates Team New Zealand 9 to 8, and New Zealand has since won in 2017, 2021, and 2024.

• A New York court had to decide whether the Great Lakes count as an arm of the sea, and ruled that they do.
• The Deed limits single masted boats to 44 to 90 feet on the load waterline unless both sides agree otherwise.
• Oracle Team USA spent an estimated 300 million dollars on its 2013 campaign.
• Peter Burling holds the record for match wins at 22 to 6, while Russell Coutts went 14 and 0.
• From 1928, Goodyear named blimps after Cup winning yachts such as America, Puritan, and Reliance.

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Bartolomeu Dias was born around 1450 into a Portuguese seafaring family: his ancestor Dinis Dias had reached the Cape Verde peninsula in the 1440s. Records place him at the building of São Jorge da Mina in 1481 and likely on Diogo Cão's voyages to the Congo, and by 1486 he was a cavalier at King John II's court and superintendent of the royal warehouses, paid an annuity for services to come. Around July 1487 he left Lisbon with the caravels São Cristóvão and São Pantaleão, a supply ship under his brother Diogo, and pilot Pero de Alenquer, carrying stone padrões and six Africans kidnapped on earlier voyages to act as emissaries. The goals were to find the bottom of Africa and intelligence on Prester John, an ally against the Ottoman and Venetian grip on the spice trade.

Fighting the cold northward Benguela Current, Dias turned away from the coast and sailed southwest into the open Atlantic for 30 days, catching westerlies in the maneuver later called the volta do mar. Turning east, he found no coast, and in February 1488 landed at what is now Mossel Bay, having rounded Africa without seeing it. At Kwaaihoek in March the crew forced a return, and only then, in May 1488, did he see the headland he named the Cape of Storms, which the king rebranded the Cape of Good Hope. He was sidelined for a decade, passed over for Vasco da Gama, and assigned to design da Gama's ships. Sailing with Pedro Álvares Cabral's fleet, which reached Brazil in April 1500, he died when a storm sank four ships near the same cape on May 29, 1500.

• The supply ship left in Angola was riddled with shipworms, and six of its nine guards had been killed.
• His fleet returned to Lisbon in December 1488 after 16 months, to a muted, secretive welcome.
• He designed the São Gabriel and São Rafael as sturdier square rigged naus for the Southern Ocean.
• The original logs of his voyage were destroyed with the Casa da Índia in the 1755 Lisbon earthquake.
• His grandson Paulo Dias de Novais founded Luanda, and Mossel Bay displays a life size replica of his caravel.

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Auguste Piccard, born in Basel, Switzerland in 1884 alongside his twin brother Jean-Félix, studied at the ETH in Zurich, became a physics professor at the Free University of Brussels in 1922, and sat at the Solvay Congresses with Marie Curie, Niels Bohr, and Albert Einstein. Physicists needed clean measurements of cosmic rays, which the atmosphere degrades, so with funding from the Belgian FNRS he designed a sealed, pressurized aluminum gondola to hang beneath a hydrogen balloon. On May 27, 1931 he and assistant Paul Kipfer launched from Augsburg, Germany wearing improvised pillow helmets, rose to 15,781 meters, and became the first humans to enter the stratosphere, proving the pressurized cabin concept that airliners depend on today.

Piccard then ran the math in reverse for the deep sea. His bathyscaphe used a thick steel sphere to resist crushing pressure, a float filled with gasoline because liquid barely compresses, and iron ballast held by a magnetic release that dropped the weights to let the craft rise. World War II delayed the work until 1945. The FNRS-2 made unmanned dives in 1948, the French Navy later took a redesigned version past 4,100 meters in 1954, and in 1953 Auguste and his son Jacques dove a second bathyscaphe to 3,150 meters. He died of a heart attack in Lausanne in 1962 at 78.

• The pressure he faced deep down exceeded 6,700 pounds per square inch, like three elephants on a postage stamp.
• A sphere spreads pressure evenly with no corners to act as weak points.
• He and Kipfer are credited as the first humans to directly observe the curvature of the Earth.
• Hergé based Tintin's Professor Calculus on the tall, long necked Piccard he saw in Brussels.
• Gene Roddenberry named Captain Jean-Luc Picard in honor of Auguste and Jean-Félix Piccard.

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The Vendée Globe is a solo, nonstop, unassisted race around the world over roughly 44,000 kilometers, about 24,000 nautical miles. It was created as the Globe Challenge by French sailor Philippe Jeantot, who had twice won the staged BOC Challenge in the 60 foot class (1982 to 1983 and 1986 to 1987) and wanted to remove the safety net of port stops. The first edition in 1989 to 1990 had 13 starters and was won by Titouan Lamazou in just over 109 days, with Jeantot finishing fourth. Since 1992 it has run every four years from Les Sables d'Olonne, down the Atlantic, past the Cape of Good Hope, clockwise around Antarctica leaving Cape Leeuwin and Cape Horn to port, and back north, timed from November to February for the austral summer.

The rules ban any outside help, including external weather routing, so sailors download raw GRIB files and plot their own routes on onboard computers while sleeping in 20 to 40 minute bursts. After Canadian Gerry Roufs was lost in the 1996 to 1997 race, organizers added a GPS ice exclusion zone that squeezes the fleet between Southern Ocean storms and drifting icebergs. Foiling IMOCA 60s changed everything: in 2024 to 2025 Charlie Dalin finished aboard Macif Santé Prévoyance in 64 days, 19 hours and 23 minutes, and Sébastien Simon covered 615 nautical miles in 24 hours. Of 238 starters only 146 have finished, 152 starters have been French, and every overall winner has been French.

• A sailor who breaks down early may return to the start to repair, but only within a 10 day window.
• Qualifying can mean a solo passage of at least 2,500 nautical miles at an average of 7 knots.
• Sailors wear crash helmets and body armor inside cabins where carbon fiber noise requires noise cancelling headsets.
• Michel Desjoyeaux is the only two time winner, taking the 2000 to 2001 and 2008 to 2009 editions.
• Ellen MacArthur finished second in 2000 to 2001, one of 15 women to compete, with starters aged 23 to 66.