Energy
50 points from the earliest roots to the research frontier: 33 researched, 7 current research, 5 unsolved and 5 that become possible once they are solved. State of knowledge: October 2026.
Open the interactive tree →Prehistorybefore 3000 BC
- Draft Animals & Muscle Power~4000 BCResearchedOxen and donkeys pull ploughs and loads - for the first time the work no longer comes from humans alone.
Antiquity3000 BC – 500 AD
- Water Wheel~250 BCResearchedFlowing water drives mills - the first major power source that does not come from muscles.
Middle Ages & Renaissance500 – 1700
- Windmill~1185ResearchedWind is harnessed on purpose for the first time: grinding, drainage and sawing, even where there is no river.
Industrial Age1700 – 1900
- Wood, Charcoal & Coal~1709ResearchedThe switch from wood to coal (coke, 1709) delivers heat on an industrial scale.
- Steam Engine1712ResearchedHeat from coal becomes motion - work is no longer tied to rivers, wind or muscle.
- Voltaic Pile (First Battery)1800ResearchedVolta stacks metal discs with brine-soaked cloth in 1800 and gets a steady electric current for the first time.
- Water Turbine1827ResearchedFourneyron's turbine (1827) turns flowing water into rotation far more efficiently than a water wheel and works at large heads and flows.
- Dynamo & Electric Motor1831-1866ResearchedFrom Faraday's disc (1831) to Siemens' self-exciting dynamo (1866), machines convert motion into current and back.
- Fuel Cell1839ResearchedWilliam Grove shows in 1839 that hydrogen and oxygen can combine in a cell to give electricity directly, without burning anything.
- Oil & Natural Gas1859ResearchedThe first oil well in Pennsylvania opens up the liquid fuel that powers the 20th century.
- Rechargeable Battery1859ResearchedThe lead-acid battery stores electricity chemically and can be recharged - electricity becomes storable.
- Incandescent Light Bulb1879ResearchedSwan and Edison (1879) make a long-lasting electric lamp; clean light creates the demand for power stations and grids.
- Electrification1882ResearchedCentral power stations and grids turn electricity into energy that anyone can get from any socket.
- Hydroelectric Power1882ResearchedA water turbine driving a dynamo gives electricity from rivers: the Vulcan Street plant (1882) was among the first, Niagara (1895) the first giant.
- Steam Turbine1884ResearchedParsons' steam turbine (1884) spins fast and smooth, driving generators and ships far more efficiently than piston engines.
- Transformer1885ResearchedThe closed-core transformer (1885) raises and lowers AC voltage, so power can travel far on thin wires and be used safely at home.
- AC Induction Motor1888ResearchedA motor with no electrical contact to its rotor (Ferraris, Tesla, 1885-88) runs straight from AC power and became the workhorse of industry.
- Pumped-Storage Hydropower~1890ResearchedSurplus power pumps water uphill and later runs it back through turbines: the oldest and still largest way to store grid electricity.
- AC Power & Large Power Plants1895ResearchedThe Niagara power station and high voltage: electricity can be sent tens of kilometres away.
Machine Age1900 – 1945
- Air Conditioning1902ResearchedWillis Carrier's 1902 system controls both temperature and humidity; cool air makes hot-climate cities, factories and data centres workable.
- Geothermal Electricity1904ResearchedAt Larderello in Italy (1904) natural steam from the ground first drives a generator: the Earth's own heat becomes electricity.
- Gas Turbine Power Plant1939ResearchedIn 1939 a Brown Boveri gas turbine at Neuchâtel is the first to generate public electricity; combined-cycle gas plants later reach about 60 %…
- First Nuclear Reactor (CP-1)1942ResearchedOn 2 December 1942 Fermi's team in Chicago starts the first self-sustaining nuclear chain reaction.
Atomic & Space Age1945 – 1990
- HVDC Power Transmission1954ResearchedDirect-current links like the Swedish Gotland cable (1954) move large amounts of power over very long distances with small losses.
- Nuclear Power1954ResearchedSplitting uranium delivers heat for electricity - about 8.5% of world power in 2025.
- Photovoltaics1954ResearchedThe Bell Labs silicon solar cell turns light into usable electricity for the first time - 6% efficiency.
- Superconducting Magnets1961ResearchedNiobium-tin wire (Bell Labs, 1961) carries huge currents without loss, making very strong magnets for accelerators, MRI and fusion machines.
- Tokamak & Stellarator1968ResearchedMagnetic bottles for hot plasma: in 1968 the Soviet tokamak T-3 reaches temperatures needed for fusion.
- Nuclear Accidents & Safety Turn1979-1986ResearchedThree Mile Island (1979) and Chernobyl (1986) stalled new reactor orders in the US and drove international safety conventions and the operators'…
- Modern Wind Turbines~1980ResearchedDanish and Californian turbines of the 1980s turn the windmill into a power generator.
Digital Age1990 – 2015
- Lithium-Ion Battery1991ResearchedLight, rechargeable, energy-dense: Sony brings the first lithium-ion battery to market in 1991.
- Offshore Wind Farms1991ResearchedDenmark's Vindeby farm (1991) puts eleven turbines in the sea, where wind is stronger and steadier than on land.
- Shale Revolution (Fracking)~2008ResearchedSlickwater fracturing and horizontal drilling made shale rock a main source of gas and oil; US shale gas rose from 5.9% of gas output in 2006 to 23%…
Present2015 – Oct 2026
- Solar Boom & Price Collapse2015–2026Current researchAbout 647 GW of solar went online worldwide in 2025; solar overtook wind for the first time and met 75% of demand growth.
- New Reactors & SMRs2020–2026Current researchNuclear power set a generation record in 2025 (2,702 TWh); on 30 September 2026 the US issued its first construction permit for a commercial SMR.
- Fusion: Ignition & Records2022–2026Current researchNIF ignites repeatedly (record 8.6 MJ, gain 4.13); Wendelstein 7-X, WEST and EAST set duration records; capital floods into start-ups.
- Heat Pumps Scale Up2022–2026Current researchHeat pumps have outsold gas boilers in the US every year since 2022 and in Germany in 2025, yet supply under 15% of the world's building heat.
- Grid-Scale Batteries2025Current research112 GW (307 GWh) of grid batteries were commissioned in 2025; battery packs for stationary storage now cost only about $70/kWh.
- Sodium-Ion & Solid-State Cells2025–2026Current researchCATL and Changan unveil what they call the world's first mass-produced sodium-ion passenger car (2026, company claim); solid-state cells stay at…
- Enhanced Geothermal (EGS)2026Current researchIn September 2026 Fervo's Cape Station in Utah entered commercial operation - its first 33-MW block is what Fervo calls the first greenfield EGS…
Research Frontier · Todayunsolved as of Oct 2026
- Cheap Green HydrogenopenUnsolvedHydrogen from renewable power still costs more than fossil hydrogen; low-emission hydrogen is under 1% of use and the 2030 project pipeline shrank.
- Final disposal of nuclear wasteopenUnsolvedSpent nuclear fuel must stay isolated for 100,000+ years; the first deep repository for it is only now nearing its operating licence, in Finland.
- Net-Electricity Fusion PlantopenUnsolvedNo fusion device has yet delivered net electricity; ignition has been shown, the power plant as a whole has not.
- Seasonal Energy StorageopenUnsolvedBatteries bridge hours, but wind and sun vary over weeks and seasons - an affordable TWh-scale store is missing.
- Stable 100% Renewable GridopenUnsolvedWithout spinning power-plant mass, inertia and voltage support are missing; how such a grid runs safely is still open.
If Solvedbecomes possible
- Fusion Power Plants on the Grid2040s?If solvedThe first fusion power plants feed in reliably and become the new baseload.
- Green Hydrogen Economy2040s?If solvedHydrogen from renewable power replaces coal and natural gas in steel, chemicals, fertiliser and parts of shipping and aviation.
- All-Renewable Energy Supply2050s?If solvedWhole countries cover their energy needs year-round from sun, wind and water - electric power, heat and transport.
- Nuclear Waste Safely Sealed2060s?If solvedSeveral countries operate deep repositories for spent fuel, with sites accepted by their host communities and monitoring in place.
- Fusion Spacecraft PropulsionopenIf solvedCompact fusion reactors power spacecraft and shorten trips to Mars and asteroids significantly.