Ship

• 1. Introduction

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  A ship carries a boat, but a boat cannot carry a ship. That simple rule of thumb is one of the few ways anyone has reliably told the two apart, because there is no universally accepted distinction between them. The US Navy offers another test: ships heel toward the outside of a sharp turn, boats toward the inside, a difference of where the center of mass sits against the center of buoyancy. A ship is a large watercraft built to move across water, hauling cargo or passengers or doing specialized work like warfare, oceanography and fishing. Ship transport carries the largest portion of world commerce. So how did a vessel made of planks come to move more goods than any other machine on earth? Why was sea travel for most of history cheaper, safer and faster than the same trip overland? And why, after thousands of years, did a Member of Parliament have to paint a circle on the side of every hull?

• 2. The Cheapest Road

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  It cost less for a Roman sailing ship to carry grain the length of the Mediterranean than to move the same amount fifteen miles by road. Cities like Rome depended entirely on that arithmetic. Rome consumed about 150,000 tons of Egyptian grain each year over the first three centuries AD, delivered by sailing and oar-powered ships. For most of history, transport by ship has generally been cheaper, safer and faster than the same journey on land, provided a feasible route existed. Only two inventions overturned that principle. The coming of railways in the middle of the 19th century was the first. The growth of commercial aviation in the second half of the 20th century was the second. Until those arrivals, ships were generally the most advanced expressions of the technology available to the societies that built them.

• 3. Sails Across Half The Globe

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  Austronesian peoples originated in what is now Taiwan, and from there they spread across a territory spanning half the globe. Their crab claw sails, possibly raised before 2000 BC, let them cross vast stretches of open ocean. From Taiwan they colonized Maritime Southeast Asia, then Micronesia, Island Melanesia, Polynesia and Madagascar. Their sails were woven from leaves, usually from pandan plants, and paddlers often stood on platforms set on the outriggers of larger boats. By the 2nd century AD, people from the Indonesian archipelago were building ships over 50 meters long that stood 4 to 7 meters out of the water. These vessels carried 600 to 1000 people and 250 to 1000 tons of cargo across the waves. The Chinese called them kunlun bo, ship of the Kunlun people, and the Greeks called them kolandiaphonta. With 4 to 7 masts and tanja sails, they could sail against the wind, and may have reached as far as Ghana. In the 11th century a new ship, the djong or jong, was recorded in Java and Bali, built from wooden dowels and treenails rather than the vegetal-fiber lashings of the kunlun bo.

• 4. The First True Seafarers

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  The earliest historical evidence of boats is found in Egypt during the 4th millennium BC. The Greek historian Agatharchides recorded that during the Old Kingdom, between the 30th and 25th centuries BC, Egyptian ships sailed the Red Sea as far as the myrrh-country. One stunning relic of their skill is the Khufu ship, a vessel 143 feet long entombed at the foot of the Great Pyramid of Giza around 2500 BC and found intact in 1954. The oldest discovered seafaring hulled boat is the Uluburun shipwreck, found off the coast of Turkey and dating to 1300 BC. By 1200 BC the Phoenicians were building large merchant ships. Richard Woodman calls them the first true seafarers, the founders of pilotage, cabotage and navigation, and the architects of the first true ship built of planks, capable of carrying a deadweight cargo and being sailed and steered.

• 5. Two Traditions Merge

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  Until the late 13th or early 14th century, European shipbuilding ran in two separate streams. In Northern Europe, clinker construction predominated: hull planks fastened in an overlapping shell, with the ribs fitted afterward. These ships set a single square sail on one mast and steered with a rudder. The Mediterranean tradition used carvel construction instead, fitting smooth hull planking to a frame built first, rigged with lateen sails and steered by a side rudder. Then the two streams met. Cogs reached the Mediterranean in the 12th and 13th centuries, and by early in the 14th century Mediterranean shipwrights were copying their designs. The result combined a square sail on the mainmast with a lateen on the mizzen and a sternpost rudder, a vessel called a coche or, when larger, a carrack. In the first two decades of the 15th century, the English captured a few of these, two of which had been chartered to the French. By the late 1430s, carvel ships were being built in Northern Europe in growing numbers. This hybrid produced the full-rigged ship: three masts, square-rigged foremast and mainmast, lateen on the mizzen. It carried the explorers of the Age of Discovery, and over four centuries gave rise to the galleon, the fluit, the East Indiaman, the clipper and many more. The switch from clinker to carvel also let builders fit gunports and frame hulls strong enough to bear the weight of artillery at sea.

• 6. Steam Outruns Sail

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  Higher boiler pressures of 60 psi, powering compound engines, were introduced in 1865 and made long-distance steam cargo viable on the route from England to China, even before the Suez Canal opened in 1869. Within a few years, steam had replaced many of the sailing ships on that run. For more than half of the 19th century, steam and sail coexisted. Steam first paid only on shorter routes, carrying mail and passengers who could afford higher fares. Screw propulsion beat paddle wheels, but it depended on an effective stern gland for the propeller shaft. Greater efficiency came from triple-expansion engines, which needed higher quality steel for boilers running at 125 psi, achieved in SS Aberdeen in 1881. After that, virtually every route could be served by steamships, though sail held on for cargoes where low cost mattered more than speed. Parallel to merchant vessels, navies were building their own giants. During the first half of the 18th century, the French Navy developed the ship of the line, carrying seventy-four guns. These ships were 56 meters long and required 2,800 oak trees and 40 kilometers of rope, with a crew of about 800 sailors and soldiers. The Second Industrial Revolution and the ability to build hulls from metal triggered an explosion in ship design, producing ocean liners and, from the 1960s onward, the container ships that reshaped merchant shipping.

• 7. The Line On Every Hull

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  In Britain until Samuel Plimsoll's Merchant Shipping Act of 1876, ship-owners could load their vessels until the decks were almost awash. A sailor who signed on, recognized the danger, and chose to leave could end up in jail. Plimsoll, a Member of Parliament, engaged engineers to derive a formula for a line on a hull that, when it reached the water during loading, marked the maximum safe level. That mark survives as the Plimsoll mark, a circle with a horizontal line through its center, replaced by a diamond on the Great Lakes. Because summer, fresh, tropical fresh and winter north Atlantic water differ in density, later rules added a ladder of load lines forward of the circle. Modern hulls hide compartments below those marks. Ballast tanks change a ship's trim and stability, and that same seawater carries an unintended passenger. Mnemiopsis leidyi, a comb jelly, was introduced to the Black Sea in 1982, thought to have arrived in a ship's ballast water. By 1988 it was wreaking havoc on the local fishing industry. The anchovy catch fell from 204,000 tons in 1984 to 200 tons in 1993.

• 8. Threats In The Water

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  An oil tanker can carry 2 million barrels of crude, or 84 million US gallons, more than six times the amount lost in the Exxon Valdez incident. In that grounding in March 1989, the ship dumped 10.8 million US gallons into the ocean, killing over 400,000 seabirds, about 1,000 sea otters and immense numbers of fish. The International Tanker Owners Pollution Federation studied 9,351 accidental spills since 1974 and found most came from routine operations like loading, discharging, and taking on fuel. 91 percent of operational spills were small, under 7 tons, while 84 percent of accident spills involved losses over 700 tons. Following Exxon Valdez, the United States passed the Oil Pollution Act of 1990, requiring tankers in its waters to be double-hulled by 2015. After the sinkings of Erika in 1999 and Prestige in 2002, the European Union required double hulls by 2010. Exhaust adds a second threat: seagoing vessels are responsible for an estimated 14 percent of nitrogen emissions and 16 percent of sulfur emissions from fossil fuels into the atmosphere. As of 2024, new ships are increasingly built with alternative fuel capability, drawing on LNG, LPG, methanol, biofuel, ammonia and hydrogen, while wind power for ships has drawn renewed interest for cutting greenhouse gas emissions.