From a campfire a million years ago to steam, oil, nuclear power and a small sun on Earth
Fire was the first time humans used energy from outside their own bodies. Cooking food, warding off cold and predators, and burning forests into grassland, people began for the first time to change nature with energy.
Using energy outside the body.
Traces of fire use about a million years old were found at Wonderwerk Cave in South Africa. Habitual, controlled use of fire becomes certain from several hundred thousand years ago.
Did fire make us human?
Cooked food is easier to digest and yields more calories. The anthropologist Richard Wrangham proposed that cooking let our ancestors divert energy from digestion to the brain, making the large human brain possible. It also created social time, gathered around the fire telling stories.
Burning forests into grassland.
Hunter-gatherers set fires to burn forests into grassland that drew game. Fire let people spread into cold regions, and it was the first time humans changed nature on a large scale with energy.
Farming is, at bottom, a system for capturing solar energy in plants and harvesting it. It yielded far more calories from the same land than hunting and gathering, and populations grew and cities appeared. For nearly 10,000 years after, civilization ran on human and animal muscle and heat from burning wood. The limits to growth were the amount of land and the efficiency of photosynthesis.
Fields that gather solar energy.
Farming, which began in the Fertile Crescent, produced far more food from the same land. On this surplus energy rose cities, writing, mathematics, and city walls.
Muscles stronger than ours.
Domesticating cattle, horses, donkeys and camels gave people power far greater than human muscle. A single ox can do the work of several people.
The ox-drawn plow.
The ox-drawn plow appeared, letting farmers cultivate far more land than digging with a hoe.
Moving loads by cart.
With the invention of the wheel, combined with animal power, carts appeared and heavy loads could be moved.
The great buildings of antiquity were built by the muscles of countless people, and slave labor was both a terrible social institution and, in effect, the most important power source. Charcoal for smelting metal stripped the Mediterranean of its forests. Energy shortages and environmental damage were problems from the start. Wind and water became the first mechanical power beyond muscle.
The first mechanical power that wasn't muscle.
In Egypt, sails were fitted to boats traveling the Nile. For thousands of years after, wind powered sea trade and exploration.
Buildings made by countless muscles.
The great structures of antiquity, the pyramids, the Great Wall, the roads of Rome, were all built with human muscle. In ancient Greece and Rome, slave labor was in effect the most important power source. The forests along the Mediterranean shrank sharply to make the charcoal needed to smelt bronze and iron.
Grinding grain with flowing water.
In the Greek world appeared the water wheel, turned by flowing water to grind grain. In the 2nd century, at Barbegal in Roman southern France, sixteen water wheels in a staircase down a hillside formed the largest milling complex of the ancient world.
The ancestor of the steam engine, 1,700 years early.
Hero of Alexandria built a ball that spun as it jetted steam. In principle it was the ancestor of the steam engine, but it was used only as a temple curiosity. Explanations range from cheap slave labor making machines unnecessary to the lack of precise metalworking.
Often seen as a stagnant era, the Middle Ages actually used far more mechanical power than antiquity. Water wheels turned in every village, windmills drew power from flat land, and the efficiency of the horse rose sharply. In China, coal came into large-scale use first.
Power without a river.
Vertical-axis windmills appeared in Persia, and in 12th-century Europe windmills with sails turning on a horizontal axis developed. Power could now be had even on flat land without rivers.
The horse replaces the ox.
As the horse collar, which let a horse pull with its shoulders without choking, and iron horseshoes spread, horses pulled plows and carts much faster and more efficiently than oxen. European farm productivity rose sharply.
A coal economy before the Industrial Revolution.
Short of forests, Song China began burning coal on a large scale and used it to mass-produce iron; by some estimates its iron output rivaled that of all of Europe on the eve of the Industrial Revolution. But the trend did not continue, and why the Industrial Revolution happened in Britain rather than China remains a major debate.
One in every village.
England's great land survey recorded about 5,600 water mills. They ground grain and also fulled wool, worked forge bellows, sawed timber and made paper.
As its forests disappeared, Britain was forced to switch to coal. As mines went deeper, the steam engine was born to pump out the rising water. A machine for digging coal ran on coal.
The peak of an energy economy before fossil fuels.
The Netherlands used thousands of windmills to pump water, saw timber and grind grain, burned peat dug from its bogs, and became the richest country in Europe. The Golden Age of Rembrandt and Vermeer stood on this energy.
Hemispheres even horses couldn't pull apart.
Research in physics on the vacuum and air pressure laid the groundwork for the steam engine. Guericke showed the enormous force of the atmosphere with metal hemispheres, emptied of air, that teams of horses could not pull apart. In 1690 Papin proposed condensing steam to create a vacuum and using air pressure to move a piston.
Air pollution before the Industrial Revolution.
As population grew and shipbuilding and ironmaking expanded, the forests disappeared and Britain switched its heating to smoky, smelly coal. The writer John Evelyn published a protest against London's air, thick with coal smoke. Britain was lucky to have plenty of coal underground.
Drawing water up with steam.
Savery patented a pump that used steam to draw water out of mines. It was dangerous and inefficient, but it was the first attempt to put steam power to practical use.
Making iron without charcoal.
Abraham Darby succeeded in smelting iron with coke, made by baking coal. Without the need for charcoal from forests, iron could be made in almost unlimited quantities.
The first steam engine put to practical use.
Steam was let into a cylinder and sprayed with cold water to condense it, creating a vacuum, and air pressure pushed the piston down. Only about 1% of the fuel became work, but at a mine entrance, where coal was practically free, it was worth using.
In energy terms, the Industrial Revolution was the moment humanity first escaped the limits of the plants growing on the land each year and began tapping fossil energy stored over hundreds of millions of years. The economic historian E.A. Wrigley called it the shift from an organic economy to a mineral economy. And thermodynamics was born from the effort to understand the steam engine.
Keep the cylinder hot, and condense elsewhere.
Repairing a model Newcomen engine, James Watt realized that if the steam was cooled in a separate condenser outside the cylinder, the cylinder could stay hot. Fuel efficiency improved several times over. He rated engines by how many horses' work they did (horsepower), and the watt, the unit of power, is named after him.
The steam engine turns every machine.
Watt added a mechanism that turned the piston's back-and-forth motion into rotation. Now the steam engine could drive every machine in a factory, not just pump water, and factories could be built anywhere rather than beside rivers. Workers flooded into cities, and industrial towns such as Manchester grew explosively.
Crossing oceans without wind.
Robert Fulton in the United States ran a commercial steamboat, and steamships went on to cross oceans without depending on the wind. They laid the groundwork for ironclads and imperialism.
Technology gives birth to science.
Carnot asked whether a heat engine's efficiency has a theoretical limit and showed that it depends only on the temperature difference between the hot and cold sides. Joule, Helmholtz, Clausius and Kelvin then established the laws of energy conservation and entropy. Usually science gives birth to technology, but the steam engine was built first, without theory, and thermodynamics was born from trying to understand it.
Running over land faster than a horse.
The year before, Stephenson's locomotive Rocket had won a trial race, and the first true passenger and freight railway opened. For the first time, people traveled over land faster than a horse.
Oil replaced whale oil and soon fueled the internal combustion engine. Electricity was not an energy source but a new way to carry and distribute energy, gathering any source together and sending it anywhere. The geopolitics of oil began, and fossil fuels became food by way of fertilizer.
Oil saves the whales.
Whale oil, the premium fuel for lighting the night, had soared in price from overhunting. Drake drilled into the ground by machine in Pennsylvania and pumped out oil, and refined kerosene replaced whale oil. At first gasoline was thrown away as a useless byproduct.
Greater efficiency means more consumption.
In The Coal Question, the economist William Stanley Jevons pointed out that although Watt had made the steam engine more efficient, coal consumption had exploded. Greater efficiency makes energy cheaper to use, so it gets used in more places. The point is still cited in debates over energy conservation and the power used by AI data centers.
A monopoly on oil refining.
Rockefeller took control of most American oil refining and became one of the richest people in history. In 1911 antitrust law split the company into more than 30 pieces, whose descendants include today's ExxonMobil and Chevron.
Burning fuel inside the cylinder.
Otto built the four-stroke gasoline engine. Burning fuel directly inside the cylinder made it far smaller and lighter than a steam engine, and discarded gasoline suddenly became a key fuel. Benz's gasoline car of 1886 and Diesel's engine of the 1890s followed.
Power plant, wires, meters and bulbs in one system.
After making a long-lasting incandescent bulb practical in 1879, Edison opened the first commercial power station in New York. More important was the system that tied everything from the generating station to the light bulb together. The principle was Faraday's electromagnetic induction.
The heart of today's power plants.
Parsons invented the turbine, which uses steam to spin a bladed wheel at high speed. It was far more efficient than piston engines and could be built much bigger. Most coal, gas and nuclear plants today still work by boiling water to drive steam turbines. A nuclear plant is a giant kettle.
The end of the war of the currents.
Edison's direct current lost so much power over distance that it could serve only areas near the station. Tesla and Westinghouse pushed alternating current, which transformers could step up for long-distance transmission, while Edison fought back, claiming AC was dangerous and even staging electrocutions of animals. When AC won at the 1893 Chicago World's Fair and at the Niagara Falls hydroelectric plant, the structure of today's grid was set.
A warning that seemed far off.
The chemist Svante Arrhenius calculated that doubling the carbon dioxide in the atmosphere would raise the Earth's temperature by several degrees. At the time it seemed a matter for the distant future.
The car for everyone.
Ford released the cheap Model T and in 1913 introduced the assembly line, putting the car within reach of the masses. Demand for oil exploded.
The choice of a country with coal but no oil.
Churchill, First Lord of the Admiralty, decided to switch Britain's warships from coal to oil. Oil was lighter and more efficient and made ships faster, but Britain had no oil of its own. The British government bought a stake in the Anglo-Persian Oil Company (today's BP), and the geopolitics of Middle Eastern oil began.
We are eating fossil fuels.
A process that uses enormous energy to make fertilizer from nitrogen in the air went into large-scale operation. Much of the food humanity eats today depends on this fertilizer. Fossil fuel had inserted itself into the 10,000-year chain from sun to plant to food.
Electricity became a symbol of modernization itself and spread to the countryside and the home. Giant oil fields were found in the Middle East, and World War II became in large part a war over oil. And nuclear fission opened the door to an entirely new form of energy.
Communism is Soviet power plus electrification.
Lenin said this as he launched a plan to electrify the whole country. Electricity was the symbol of modernization itself. Appliances such as washing machines, refrigerators and vacuum cleaners would transform housework, especially women's labor.
Electricity reaches the countryside.
During the Great Depression, through the Tennessee Valley Authority, the Hoover Dam (1936) and rural electrification programs, the United States brought electricity, until then mostly urban, to the countryside.
Two doors opened in the same year.
A huge commercial oil field gushed at Dhahran in Saudi Arabia, following a string of giant discoveries in the Middle East in the 1930s, including Kuwait. Late the same year, nuclear fission, the splitting of the uranium nucleus, was discovered in Germany. Neutrons released by a split nucleus can split other nuclei in a chain reaction: unleashed in an instant, it is a bomb; controlled slowly, a power plant.
Oil decides a war.
The US cutoff of oil exports to Japan was one of the main causes of the attack on Pearl Harbor. Germany aimed for the oil fields of the Caucasus and held out by making synthetic fuel from coal. Tanks, fighters and aircraft carriers all ran on oil.
Nuclear power was born as part of a bomb project.
In Chicago, Fermi produced a controlled chain reaction in the first nuclear reactor.
After the war, cheap oil flooded the world, and cars, suburban homes, air travel, plastics and global trade exploded. Nuclear power moved from military to civilian use, promising electricity "too cheap to meter." In the same period the solar cell was invented and carbon dioxide measurements began.
The first light bulbs lit by nuclear power.
EBR-I, an experimental reactor in Idaho, generated electricity from nuclear power for the first time and lit a few light bulbs. In 1953 Eisenhower proposed the peaceful use of nuclear energy in his "Atoms for Peace" speech at the UN.
Nuclear power on the grid, and the light-water reactor in a submarine.
The Obninsk plant in the Soviet Union supplied electricity to the grid for the first time, followed by Calder Hall in Britain in 1956 and Shippingport in the US in 1957. The same year, Admiral Rickover of the US Navy chose a compact, rugged light-water reactor for the nuclear submarine Nautilus, and as that technology and its people moved straight into civilian power plants, the light-water reactor became the world's dominant design. Historians of technology cite it as a classic case of path dependence.
The most famous failed prophecy in nuclear history.
The chairman of the US Atomic Energy Commission boasted that nuclear electricity would be too cheap to meter.
Six percent efficient, for satellites only.
Bell Labs invented the silicon solar cell. About 6% efficient and very expensive, it was used at first only to power spacecraft such as the Vanguard 1 satellite of 1958.
US oil production will peak and decline.
The geologist M. King Hubbert predicted that US oil production would peak around 1970 and then decline, and it did. But the world's peak kept being pushed back by new fields and shale technology.
Carbon dioxide rising year after year.
Charles David Keeling began precise measurements of atmospheric carbon dioxide at Mauna Loa in Hawaii, and the curve rising steadily every year became the symbol of climate science.
Oil producers join hands.
Saudi Arabia, Iran, Iraq, Kuwait and Venezuela formed the Organization of the Petroleum Exporting Countries. Around the 1960s oil overtook coal as the world's largest energy source.
When oil became a weapon, countries turned to nuclear power, energy conservation, and the sun and wind. But a string of accidents and soaring costs stalled nuclear power, and climate change rose onto the international agenda.
Oil exports cut off.
During the Arab–Israeli war, Arab oil producers cut off exports and oil prices multiplied. The 1979 Iranian Revolution brought a second oil shock. Realizing that oil dependence was a security problem, countries took their first serious interest in conservation, fuel-economy rules, nuclear power and renewables.
About 70% of electricity from nuclear.
France, which has no oil, began building nuclear plants on a massive scale right after the oil shock, and still generates about 70% of its electricity from nuclear power. It kept costs down by building the same design again and again.
Trust collapses.
At the Three Mile Island plant in the United States, a cooling failure caused part of a reactor core to melt. The radiation released was limited, but American public trust in nuclear power collapsed.
Wind grown by the oil shocks.
After the oil shocks, wind power developed in earnest in Denmark, later growing into huge offshore wind farms.
The worst accident in nuclear history.
During a safety test at the Chernobyl plant in Soviet Ukraine, a reactor exploded, spreading large amounts of radiation across Europe.
Climate change becomes an international issue.
The Intergovernmental Panel on Climate Change was established, leading to the Kyoto Protocol in 1997. If the Industrial Revolution had used fossil energy to break the limits to growth, the bill was now coming due as climate change.
Smoothing out the ups and downs of sun and wind.
As the price of the lithium-ion battery commercialized by Sony collapsed, it made electric cars and large-scale energy storage possible (Nobel Prize in Chemistry, 2019). Batteries began to cover the weakness of sun and wind, which rise and fall with the weather.
Seventy years of trying to bring the sun to Earth.
The sun releases energy as hydrogen nuclei fuse into helium. On Earth this requires confining plasma at over 100 million degrees with powerful magnetic fields, and the doughnut-shaped tokamak devised in the 1950s by the Soviet physicists Tamm and Sakharov became the world standard. In 1997 JET, the joint European machine in Britain, produced the world's largest fusion output at the time. The Kyoto Protocol was adopted the same year.
Hydraulic fracturing redrew the map of oil and gas, and Fukushima dealt nuclear power another blow. Solar prices plunged along the learning curve, and the world pledged carbon neutrality in the Paris Agreement.
Oil and gas that couldn't be extracted.
As horizontal drilling and hydraulic fracturing, breaking rock with high-pressure water, advanced, oil and gas poured out of shale formations. In 2018 the United States became the world's largest oil producer, and cheap natural gas replacing coal power even lowered American carbon emissions.
An earthquake, a tsunami and three meltdowns.
A massive earthquake and tsunami cut off power and the cores of three reactors melted. Germany decided to phase out nuclear power and closed its last plants in 2023. Along with accidents, costs and construction delays held nuclear power back, and in many Western countries new construction nearly stopped for decades.
1.5 to 2 degrees above preindustrial levels.
Almost every country agreed to hold global warming well below 2 degrees above preindustrial levels, and if possible to 1.5 degrees.
Renewables grow, but fossil fuels don't shrink.
Renewables grew rapidly, yet fossil fuels still supplied around 80% of the world's primary energy. The energy historian Vaclav Smil points out that the history of human energy has been a history not of transitions but of additions. Coal did not fully replace wood, nor oil coal; each was stacked on top, and every new source took decades to become dominant.
Solar became the cheapest electricity in history, and energy security and the power demands of AI data centers called nuclear power back. Factory-built small modular reactors (SMRs) and private fusion companies are racing, but all are still at an early stage.
Prices down more than 99% in 50 years.
Following a learning curve in which prices fall by a fixed share each time production doubles, solar module prices dropped more than 99% from the 1970s, and the International Energy Agency judged solar to be the cheapest electricity in history in many regions. The lesson that mass-producing identical products in factories makes them cheap is exactly what SMRs are aiming for. The same year Russia's floating nuclear plant on a barge, the Akademik Lomonosov, began commercial operation.
A small reactor in commercial operation.
China's high-temperature gas-cooled reactor HTR-PM was connected to the grid and began commercial operation in 2023. A fourth-generation design cooled by helium gas instead of water, it is one of the few small reactors in operation, along with the Akademik Lomonosov. Many SMRs are retrying paths set aside in the 1950s because of submarines, cooling with sodium, molten salt or helium.
The lesson of the oil shocks, and ignition after 70 years.
After Russia invaded Ukraine, Europe's dependence on Russian natural gas collapsed and energy prices soared, the same lesson as the 1970s oil shocks. In December, the US National Ignition Facility (NIF) produced more fusion energy than its lasers delivered for the first time, though still far less than all the electricity it took to power the lasers.
The wall of cost.
The flagship project of NuScale, the frontrunner among Western SMRs, was canceled as costs soared. Units 3 and 4 of the Vogtle plant in the US, completed the same year, came in seven years late and at more than double the cost. Germany closed its last nuclear plants, and Britain's JET set a world record for fusion energy just before ending operations.
AI calls nuclear power back.
As giant AI data centers began consuming enormous amounts of electricity around the clock, Microsoft signed a power deal to restart an idle reactor at Three Mile Island, and Google and Amazon signed deals with next-generation reactor companies. It is the very site that became a symbol of nuclear power's decline after the accident 45 years earlier. The same year ITER, the international fusion experiment, pushed back the start of full operation to the mid-2030s.
From national labs to private companies.
China's EAST and France's WEST set records in quick succession for sustaining hot plasma for many minutes. Private companies such as Commonwealth Fusion Systems, building compact tokamaks with high-temperature superconducting magnets, and Helion, which agreed to sell electricity to Microsoft and broke ground on a power plant, emerged as leading players in fusion. The US government set an executive-order goal of bringing three test reactors to criticality by July 4, 2026, and the BWRX-300 at Canada's Darlington site received its construction license and broke ground (first unit targeted for 2030).
Still a long road to commercial power.
In March, Natrium, the sodium-cooled reactor of Bill Gates's TerraPower, became the first non-light-water reactor to receive a construction permit from the US Nuclear Regulatory Commission, and reactor construction began in April. In June and July, test reactors from Antares, Valar Atomics and Deployable Energy reached criticality one after another, meeting the "three by July 4" goal, and in August Oklo's test reactor followed. All of them, however, were zero-power criticality, far from commercial generation. China's Linglong One, aiming to be the first commercial land-based SMR, targets operation by the end of 2026, and the fusion company General Fusion listed on Nasdaq. Whether factory mass production actually lowers costs, and how to secure special fuel (HALEU), have yet to be proven anywhere in the West. And fusion still carries the old joke that it is always 30 years away.