Engineering: quotes, facts and reflections

Related subjects

Browse this subject and connected topics.

Keep reading below, or choose a related topic to explore something different.

DriveReading mode

StillnessReading mode

WonderReading mode

WonderHistory

The Swedish warship Vasa sank in Stockholm harbour on its maiden voyage in 1628 and was raised, largely intact, 333 years later.

King Gustavus Adolphus ordered Vasa during his war with Poland–Lithuania, and with 64 guns on two decks it was one of the most heavily armed ships of its time. On 10 August 1628 it set off before watching crowds, heeled over in a gust after about 1,300 metres and sank; between 30 and 50 people died. The hull was too narrow and the upper decks too heavy for the ballast below. Most of its bronze cannons were salvaged in the 17th century, then the wreck was forgotten until Anders Franzén found it in 1956. The cold, brackish Baltic has none of the shipworms that eat sunken timber elsewhere, so when Vasa was lifted in 1961 more than 95 per cent of the ship was original. More than 45 million people have seen it since.

Ikigai DailyRead card

WonderArchitecture

A windcatcher, badgir in Persian, is a tall tower on a roof that catches passing breezes and channels them down into the rooms below. It has cooled houses in hot, dry places such as Iran for centuries, without any machinery.

The top of the tower has openings that face the wind. Air pushed in is forced down a shaft into the house, while warm air leaves through openings on the sheltered side; on still days the sun-warmed tower works like a chimney and draws air through the rooms. Yazd, a desert city in central Iran listed by UNESCO in 2017, is famous for its many windcatchers, and the one in its Dowlatabad Garden, about 33 metres high, is often described as the tallest in the world. Paired with covered water reservoirs called ab-anbars, windcatchers helped keep drinking water cool. Similar towers are found from Egypt to the Persian Gulf, and architects now study them for low-energy cooling.

Traditional Persian architectureRead card

WonderEngineering

A qanat is an underground channel, developed in ancient Persia, that brings groundwater from the foot of hills to fields and towns using gravity alone. From above, a qanat shows as a line of shaft openings across dry land.

Builders start with a 'mother well' dug down to the water table, then cut a tunnel back towards the surface on a very gentle slope, so the water flows without wearing away the channel. Vertical shafts along the route let workers lift out soil, bring in air and later clean the tunnel. The Qasabeh qanat at Gonabad in eastern Iran, dated to between 700 and 500 BCE, has a mother well more than 360 metres deep and about 33 kilometres of channels, and still carries water. In 2016 UNESCO listed eleven Iranian qanats together as a World Heritage site, recognising both the engineering and the old customs for sharing the water fairly.

Qanat water systemsRead card

WonderTrade

Shipping containers, steel boxes built to standard sizes, let cargo move from ship to lorry to train without being unpacked. Since the first container voyage in 1956, they have cut loading costs so sharply that they helped create today's global trade.

Before containers, dockworkers loaded ships one sack, crate and barrel at a time, and loading a ship could take days or weeks. The American trucking entrepreneur Malcolm McLean changed that. On 26 April 1956 his converted tanker Ideal X sailed from Newark to Houston with 58 containers on deck. McLean calculated that loading cost about 16 cents a ton, against almost six dollars for cargo loaded piece by piece. International standards for container sizes and corner fittings followed in 1968–1970, so any box could fit any crane, ship or lorry. Ports changed, many dockworkers lost their jobs, and making goods far from where they are sold became cheap.

ContainerizationRead card

WonderEngineering

Roman concrete has kept harbours, domes and aqueducts standing for 2,000 years, and small white lumps of lime inside it are one reason. When water seeps into a crack, calcium from these lumps can form new crystals that seal it.

For a long time these white lumps, called lime clasts, were taken as a sign of careless mixing. A 2023 study in Science Advances by a team at MIT led by Admir Masic proposed another explanation. The Romans, it argued, added quicklime, a highly reactive form of lime, directly to the mix, where it heats up as it reacts; this method, called hot mixing, left the lumps behind. To test the idea, the team made concrete the same way, cracked it and ran water through the cracks. Within about two weeks the cracks had sealed, while in a sample made without quicklime they did not. Volcanic ash from the Bay of Naples also added strength. A 2017 study of Roman harbour walls, led by the geologist Marie Jackson, found a different process: seawater seeping through them reacts with the volcanic ash and grows rare minerals that reinforce the concrete.

Roman concreteRead card

WonderEngineering

The Archimedes screw lifts water with a spiral blade turning inside a tilted tube: each turn traps a pocket of water and carries it upwards. Described more than 2,200 years ago, it is still used to irrigate fields, drain land and pump sewage.

Tradition credits the Greek mathematician Archimedes of Syracuse with the invention in the third century BC, but the credit is uncertain. Similar screws may already have been used in Egypt, and the historian Stephanie Dalley has argued that the Assyrian king Sennacherib watered his gardens at Nineveh with bronze screws in the seventh century BC. A famous early use comes from the Syracusia, a giant ship built for King Hiero II of Syracuse: according to an ancient account, one man could pump out the water that collected in its hull with a screw. Run in reverse, with falling water turning it, the same device now drives small hydroelectric plants.

Archimedes' screwRead card

WonderEngineering

The Tacoma Narrows Bridge in Washington State collapsed on 7 November 1940, four months after opening, when a wind of about 64 km/h set its light, flexible deck twisting until it tore apart. The disaster changed how engineers design long bridges against wind.

The bridge moved so much in the wind from the day it opened that locals nicknamed it Galloping Gertie. On the final morning the motion changed from up-and-down waves to a violent twisting, filmed by a local camera shop owner. No person died; a dog left in a stranded car was lost. The collapse is often blamed on resonance, but engineers now describe it as aeroelastic flutter: the twisting deck and the wind fed energy into each other. The investigation board included the aerodynamicist Theodore von Kármán. The replacement bridge, opened in 1950, used a deep, open truss that lets the wind pass through, and wind-tunnel tests became standard for long bridges.

Tacoma Narrows BridgeRead card

WonderArchitecture

Machu Picchu, a 15th-century Inca estate on a ridge high in the Peruvian Andes, stands on hundreds of stone terraces. They hold the steep soil in place, drain away heavy rain and gave the Inca room to grow crops.

It was built around 1450 as a royal estate for the Inca ruler Pachacuti, at about 2,430 metres. Much of its engineering is hidden: studies led by the hydrologist Kenneth Wright suggest that some 60 per cent of the construction lies underground, in foundations and layers of crushed stone that let the frequent heavy rain drain away instead of washing the slopes down. The site was never truly lost. Local Quechua farmers always knew it, and the Peruvian Agustín Lizárraga reached it in 1902. The American explorer Hiram Bingham made it world-famous in 1911. UNESCO listed it as a World Heritage Site in 1983.

Machu PicchuRead card

WonderArchitecture

Petra, the rock-carved city of the Nabataeans in southern Jordan, could thrive in the desert thanks to its water engineering: channels, dams, cisterns and reservoirs that caught springs, rain and flash floods.

The Nabataeans were an Arab people who grew rich from the caravan trade in incense and spices, and Petra was their capital. The city was at its height around the 1st century AD, until Rome annexed the kingdom in AD 106. In a region that gets only about 15 centimetres of rain a year, its channels, dams, tunnels and cisterns stored water through the dry months; the American Society of Civil Engineers estimates the system supplied 30,000 to 40,000 people. As trade routes shifted and earthquakes struck, the city declined. The Swiss explorer Johann Ludwig Burckhardt, travelling in disguise, brought it to European attention in 1812. UNESCO listed it in 1985.

PetraRead card

WonderSpace

A solar sail is a huge, ultra-thin mirror that lets a spacecraft travel on the faint push of sunlight. It needs no fuel, and the tiny push keeps adding speed for as long as light falls on it.

Light has no mass, but it carries momentum, so when it bounces off a mirror it gives it a tiny push. The idea goes back to Johannes Kepler, who noticed in the early 1600s that comet tails point away from the Sun and imagined ships sailing on a heavenly breeze. In 2010 Japan's IKAROS became the first spacecraft to use a solar sail in interplanetary space, on its way past Venus. In 2019 the Planetary Society's LightSail 2, partly funded by public donations, showed that a small satellite could raise its orbit using sunlight alone; it burned up in the atmosphere in 2022. The push is tiny, but it never runs out, so over months it adds up.

Solar sailRead card

WonderArchitecture

Hagia Sophia in Istanbul, finished in 537 as the cathedral of Constantinople, has one of the most influential interiors in architecture. Its great dome rests on pendentives, curved triangles of masonry that let a round dome sit on a square plan, and 40 windows around its base fill it with light.

Emperor Justinian I ordered the church after riots in 532 burned down its predecessor. Two scholars, Anthemius of Tralles and Isidore of Miletus, both skilled in mathematics and mechanics, designed it, and it was finished in under six years. The dome is about 31 metres across and its crown rises some 55 metres above the floor. The historian Procopius wrote that it seemed not to rest on masonry but to hang from heaven on a golden chain. Earthquakes brought part of the first dome down in 558, and it was rebuilt higher and steeper. The building was a cathedral for over 900 years, a mosque after the Ottoman conquest of 1453 and a museum from 1934, and it has been a mosque again since 2020.

Hagia SophiaRead card

WonderArchitecture

Angkor, capital of the Khmer Empire in today's Cambodia from the ninth to the fifteenth century, was ringed by giant reservoirs, moats and canals that stored monsoon rain and moved water across an urban area of about 1,000 square kilometres.

The largest reservoirs, called barays, are vast rectangles banked with earth: the West Baray, built in the eleventh century, measures about eight kilometres by two and still holds water. Moats such as the one around Angkor Wat framed temples modelled on the sacred mountain and surrounding oceans of Hindu and Buddhist cosmology. Radar and aerial surveys published in 2007, and airborne laser scanning (lidar) that saw through the forest in 2012, revealed roads, canals and house mounds across at least 1,000 square kilometres, the largest known pre-industrial settlement. Researchers still debate how much the barays watered rice fields. Tree rings show long droughts broken by intense monsoons in the fourteenth and fifteenth centuries, which damaged the network and probably contributed to Angkor's decline.

Angkor hydraulic systemRead card

WonderArchitecture

The eleven churches of Lalibela in northern Ethiopia were carved out of solid volcanic rock in the Middle Ages, each shaped from the top down inside deep trenches, and they are still a place of pilgrimage for Ethiopian Christians.

Tradition credits the churches to King Gebre Meskel Lalibela of the Zagwe dynasty, who reigned around the late twelfth and early thirteenth centuries; archaeologists think some parts are older, and the building sequence is still debated. Legend says he meant the site as a new Jerusalem after Saladin captured Jerusalem in 1187, and many places there carry biblical names, such as a stream called the Jordan. Masons first cut trenches to free a block of rock, then hollowed out rooms, columns, windows and doors from it; the most famous church, Bete Giyorgis, is shaped like a cross when seen from above. Tunnels link the churches, which are still in daily use. UNESCO listed them as a World Heritage Site in 1978.

Rock-Hewn Churches, LalibelaRead card

WonderEngineering

The Pont du Gard in southern France is a three-tier Roman bridge, 48.8 metres high, built to carry the aqueduct that supplied Nîmes across the Gardon River while keeping the very slight downhill slope that let water flow by gravity alone.

The aqueduct ran about 50 kilometres from a spring near Uzès to Nîmes, yet dropped only about 12.6 metres over its whole length, an average of some 25 centimetres per kilometre. The bridge's lower arches span the river, and a row of small arches on top carries the covered water channel. It is the tallest Roman aqueduct bridge still standing. Most historians date it to the first century AD, possibly the reign of Claudius. After the aqueduct fell out of use, around the sixth century, the bridge served for centuries as a road crossing, and parts of its second tier were cut away to let carts through. Napoleon III ordered a major restoration in the 1850s, and UNESCO listed it as a World Heritage Site in 1985.

Pont du GardRead card

WonderArchitecture

The Alhambra, the hilltop palace and fortress of the Nasrid sultans of Granada in Spain, is threaded with channels, pools and fountains that cool its courtyards, mirror its buildings and water the Generalife gardens beside it.

The Nasrids, the last Muslim dynasty in Spain, ruled Granada from 1238 to 1492. Their founder, Muhammad I, began the palace complex, and water reached the dry hilltop through the Acequia Real, the Royal Channel, which draws on the Darro River several kilometres upstream and runs by gravity along the hillside. The Generalife, a summer palace with terraced gardens, was built in the early fourteenth century. In the Court of the Lions, from the later fourteenth century, twelve marble lions carry a fountain whose water runs out in four channels, echoing the Islamic image of paradise as a garden watered by four rivers. Some of the original channels still water the gardens today.

Alhambra and GeneralifeRead card

DriveSpace

On 26 September 2022, NASA's DART spacecraft deliberately crashed into Dimorphos, a small asteroid orbiting a larger one, and cut the time it takes to circle its partner by about 33 minutes. It was the first proof that an impact can change an asteroid's path.

DART, short for Double Asteroid Redirection Test, launched in November 2021 and hit Dimorphos, about 150 metres across, at roughly 6.1 kilometres per second. Neither Dimorphos nor its partner Didymos was ever a threat to Earth; the pair was chosen because a change in the small asteroid's orbit is easy to measure with telescopes. Before the impact, Dimorphos circled Didymos every 11 hours and 55 minutes. The team would have counted a change of 73 seconds as success; the actual change was about 33 minutes, partly because the impact threw off a huge plume of rock and dust that pushed the asteroid further. A small Italian satellite, LICIACube, photographed the plume, and the European Space Agency's Hera probe, launched in 2024, is due to arrive in late 2026 to study the crater.

NASA DART missionRead card

WonderSpace

NASA's Parker Solar Probe, launched in 2018, flies through the Sun's outer atmosphere, the corona. In December 2024 it passed just 6.1 million kilometres from the solar surface, closer than any spacecraft before it.

The probe is named after the astrophysicist Eugene Parker, who in 1958 predicted the solar wind, the stream of charged particles flowing out from the Sun; it was the first NASA spacecraft named after a living person. A carbon-composite heat shield about 11 centimetres thick faces the Sun and heats to around 1,000 °C, while the instruments behind it stay near room temperature. Seven flybys of Venus shrank its orbit step by step. At its closest passes it travels at about 690,000 kilometres per hour, the fastest any human-made object has gone. In 2021 it became the first spacecraft to fly through the corona. Its measurements help explain how the solar wind is launched and how solar storms can disrupt satellites and power grids.

Parker Solar ProbeRead card

DriveBiography

Fazlur Rahman Khan, a Bangladeshi-American structural engineer, made very tall buildings cheaper to build with his 'tube' systems, in which a tower's outer walls work together to resist the wind. They shaped Chicago's John Hancock Center and the Sears Tower, now Willis Tower.

Before Khan, most skyscrapers relied on a rigid internal frame of steel columns and beams, and the taller they went, the more steel they needed to keep them from swaying in the wind. In Khan's framed tube, columns are set close together around the outside of the building and tied by deep beams called spandrels, so the whole outer wall acts like one stiff, hollow tube anchored in the ground. Working at the Chicago firm Skidmore, Owings & Merrill, he developed variations: the John Hancock Center (1969) braces its tube with giant diagonal X-shapes, and the Sears Tower (1973) bundles nine tubes together. Khan was born in Dhaka in 1929 and died in 1982.

Fazlur Rahman KhanRead card

WonderArchitecture

The Sagrada Família in Barcelona is the basilica Antoni Gaudí worked on from 1883 until his death in 1926, and it is still being built. Its tree-like columns and forms taken from nature are his, and the Nativity façade and crypt completed in his lifetime are on UNESCO's World Heritage List.

Gaudí took over the project in 1883 from the architect Francisco de Paula del Villar and turned a conventional neo-Gothic church into something new. For an earlier church he had studied arches with hanging chains: a chain hung from two points sags into a natural curve, and turned upside down that curve gives the shape in which a stone arch carries its load purely by compression. He also used ruled surfaces, curved shapes such as hyperboloids that can be built entirely from straight lines, which made complex stonework easier to cut. As an 'expiatory' church, built as an act of atonement, it is paid for by donations and today largely by visitors' tickets, one reason it has taken so long. Pope Benedict XVI consecrated it as a basilica in 2010. Gaudí is buried in its crypt.

Sagrada FamiliaRead card

DriveEngineering

Hoover Dam, built between 1931 and 1936 in the Black Canyon of the Colorado River on the Nevada–Arizona border, controls floods, stores water in Lake Mead and generates hydroelectric power for the American Southwest.

The dam was built during the Great Depression, when thousands of men came to the desert looking for work. By the official count, 96 workers died in accidents during construction. At 221 metres it was the tallest dam in the world when finished, and it created Lake Mead, the largest reservoir in the United States by capacity. Its water is shared among seven US states under the 1922 Colorado River Compact, and with Mexico under a 1944 treaty. So much of the river is now taken for cities and farms that it rarely reaches the sea. In 2022, after years of drought, Lake Mead fell to its lowest level since it was first filled.

Hoover DamRead card

DriveTrade

The Suez Canal in Egypt, opened in 1869, links the Mediterranean to the Red Sea, so ships between Europe and Asia no longer have to sail around Africa. Dug partly by forced labour and later fought over by empires, it still carries a large share of world trade.

The French diplomat Ferdinand de Lesseps led the company that dug the canal. In its early years tens of thousands of Egyptian peasants were made to work on it under the corvée, a system of compulsory unpaid labour, until the practice was stopped in 1864. Egypt's debts later forced it to sell its 44 per cent stake to Britain in 1875, and British troops stayed in the canal zone until 1956. That year President Gamal Abdel Nasser nationalised the canal, and Britain, France and Israel invaded. International pressure, above all from the United States, forced them to withdraw, a turning point in the end of European empire in the Middle East. In March 2021 the container ship Ever Given ran aground and blocked the canal for six days.

Suez CanalRead card

WonderArchaeology

The Schöningen spears, found in a German coal mine in the 1990s, are among the oldest known hunting weapons: wooden spears shaped and balanced for throwing. Their exact age, once put at about 400,000 years, is still debated.

A team led by the archaeologist Hartmut Thieme uncovered ten wooden weapons between 1994 and 1999 in an open-cast lignite (brown coal) mine at Schöningen in Lower Saxony, where waterlogged lakeside mud kept the wood from rotting. Most were carved from spruce trunks, one from pine, and in some the thickest point lies in the front third of the shaft, as on a modern javelin. When athletes threw replicas, they reached targets 15 to 20 metres away. The spears lay among the bones of an extinct wild horse, many with butchery marks. Their age has changed with each dating method: first 380,000 to 400,000 years, then about 300,000 to 337,000; a 2025 study argued for about 200,000 years, which would make Neanderthals their likely makers.

Schöningen spearsRead card

WonderArchaeology

The Dover Bronze Age Boat, found under a road in Dover in 1992, was built about 3,500 years ago from oak planks sewn together with yew and made watertight with moss and animal fat.

Workers building the A20 road between Folkestone and Dover uncovered the boat on 28 September 1992, six metres below the surface. Waterlogged, airless ground had kept the oak from rotting. Archaeologists worked for nearly a month to lift a 9.5-metre section; the rest ran under nearby buildings and had to be left in place. The planks are held together by twisted yew stems and by wooden wedges driven through cleats, raised blocks carved out of the planks themselves. It is dated to about 1575 to 1520 BCE, which makes it one of the oldest seagoing boats known. Whether it ever crossed the Channel is still debated. It is on display in Dover Museum.

Dover Bronze Age BoatRead card

WonderArchitecture

Chand Baori is a stepwell in Rajasthan, India: a well you reach by walking down stairs. Its 3,500 steps descend about 30 metres through 13 storeys to the water at the bottom.

Chand Baori stands in the village of Abhaneri and is said to be named after Raja Chanda, a local ruler of the Nikumbh dynasty. No inscription records its building, but its style dates it to the 8th or 9th century. In a dry region where most rain falls in a few monsoon months, stepwells stored water and let people reach it as the level dropped through the year. Here zigzag flights of steps line three sides of the square shaft, and the fourth side holds a pillared gallery with rooms. The depth also kept the air at the bottom noticeably cooler than at the surface. Beside the well stands the temple of Harshat Mata, a goddess of joy.

Chand BaoriRead card