Before computers
Simulation before the transistor: gears, water, sand and rehearsal as stand-ins for the real system.
Long before electronic computers, people built devices, models and rehearsals to stand in for systems that were too big, slow, expensive or dangerous to test directly. Gears were turned to trace planetary motion. Scale models of ships, rivers and dams were run with real water. Mechanical linkages solved equations by moving instead of calculating. Officers, midwives and children acted out scenarios with counters, sand, wax and each other. None of it was digital, and some of it is still used alongside the computer. All of it counts as simulation: a stand-in system, built to answer a question about the real one.
Orrery
A geared mechanical model of the Sun, Earth, Moon and planets, turned by hand or clockwork to show their relative motion.
Question it answers: Where will the planets and moons be relative to each other?
Leaves out: Scale completely: the planets are always represented far too close together and far too large.
Runs on: no computer. a geared mechanical model; a physical device, no digital computing at allSince: 1704 George Graham's geared planetary model, made for the Earl of Orrery
Astrolabe
A hand-held disc instrument that models the rotating sky, used to find the time, latitude and the positions of stars.
Question it answers: What time is it, and where in the sky is that star, right now?
Leaves out: Anything not on its engraved plates: a new star needs a new astrolabe.
Runs on: no computer. an engraved brass hand instrument; a physical device, no digital computing at allSince: 800 by 800, Islamic astronomers refining earlier Greek instrument designs
The Antikythera mechanism
A geared bronze device that modelled the Sun, Moon and calendar cycles well enough to predict eclipses.
Question it answers: When will the Moon eclipse the Sun next?
Leaves out: It reproduces observed cycles with gear trains and has no account of why the bodies move.
Runs on: no computer. a hand-cranked bronze gear train; a physical device, no digital computing at allSince: 150 BCE the Antikythera shipwreck device, GreeceIn the simulations tree: Antikythera mechanism
Optical planetarium
A projector inside a domed theatre casting the whole night sky, including its motion over time, onto the ceiling.
Question it answers: What will the sky over this city look like on a given night?
Leaves out: Weather and light pollution, so the stars are always visible.
Runs on: no computer. an optical star projector; a physical device, no digital computing at allSince: 1923 the first optical projection planetarium opened, Munich
Armillary sphere
Nested rings representing the celestial equator, ecliptic and horizon, built to model and measure the sky's apparent rotation.
Question it answers: Where does a given star cross the horizon, and when?
Leaves out: The planets' individual wandering, treating the sky as one rotating shell.
Runs on: no computer. a nested-ring metal or wooden instrument; a physical device, no digital computing at allSince: 117 by 117 CE, Zhang Heng's water-driven armillary sphere, China (earlier ring instruments are credited to Eratosthenes, Geng Shouchang and others but are not securely documented as nested-ring spheres) source
Equatorium
A geometric instrument with rotating plates that gives a planet's position by construction, without any arithmetic.
Question it answers: Where is this planet on the zodiac tonight, read straight off a dial?
Leaves out: Precision: it is only as good as the engraving and the eye reading it.
Runs on: no computer. a graduated brass or wooden instrument; a physical device, no digital computing at allSince: 1080 by 1080, al-Zarqali's equatorium, Islamic Spain
Terrestrial globe
A sphere carrying a map of the world, used to show distances, routes and the sizes of lands.
Question it answers: How do the continents sit relative to each other on a sphere?
Leaves out: Globes show shape and place, not the processes on the surface.
Runs on: no computer. a hand-turned model, no computationSince: 150 BCE by about 150 BCE, Crates of Mallus's globe at Pergamon, known from Strabo; Martin Behaim's 1492 Erdapfel is the oldest surviving globe source
Astronomical clock
A clock that also shows the positions of sun, moon and stars, driven by gears and an escapement.
Question it answers: Where are the sun and moon in the sky right now?
Leaves out: It reproduces fixed cycles and cannot predict anything not built into its gears.
Runs on: no computer. a gear train, no computationSince: 1092 by 1092, Su Song's water-driven clock tower, described in the Xinyi Xiangfayao source
Ship-model towing tank
A small-scale hull towed down a long tank of still water, its resistance measured and scaled up to the full-size ship.
Question it answers: How much power will the real ship need to reach a given speed?
Leaves out: Waves and weather unless the tank is built to add them.
Runs on: no computer. a towed scale hull in a water tank; a physical device, no digital computing at allSince: 1871 William Froude’s ship-model towing tank at Torquay, funded in 1870, built 1871, first test March 1872 sourceIn the simulations tree: Froude’s towing tank
Physical river basin model
A large outdoor scale model of an entire river system, complete with tributaries, built to run real water over real contours.
Question it answers: Where will the water go if this much rain falls, or this levee breaks?
Leaves out: Groundwater and most of the fine sediment detail.
Runs on: no computer. an outdoor concrete terrain model with running water; a physical device, no digital computing at allSince: 1943 the US Army Corps of Engineers' Mississippi basin model begun
Harbour and estuary model
A scale model of a port or estuary with a working tide, used to see how currents, silt and waves will move once it is built.
Question it answers: Will this new breakwater silt up the channel it is meant to protect?
Leaves out: Storms rarer than the ones the operators choose to run.
Runs on: no computer. a scale basin with a mechanical tide; a physical device, no digital computing at allSince: 1935 by 1935, European hydraulics laboratories building tidal harbour models
Dam and spillway model
A small physical replica of a dam and its spillway, run with real water to check that the design carries a flood without failing.
Question it answers: Does the spillway pass the largest flood it is ever likely to see?
Leaves out: The very largest, rarest floods, which are usually just extrapolated.
Runs on: no computer. a scale concrete model with running water; a physical device, no digital computing at allSince: 1928 US Bureau of Reclamation hydraulic model tests before a major dam
Structural scale model
A small loaded replica of a bridge or building, sometimes made from stress-revealing plastic, to see where and how it will fail first.
Question it answers: Where does this structure crack first, and under how much load?
Leaves out: Fatigue over decades, which no short test can show.
Runs on: no computer. a loaded scale replica, sometimes photoelastic plastic; a physical device, no digital computing at allSince: 1901 Coker and Filon's early photoelastic stress models
Architectural acoustic scale model
A small physical replica of a hall or theatre, tested with sound pitched up to match the model's size, to hear how the real room will perform.
Question it answers: Will the back row hear the stage clearly in this hall?
Leaves out: The audience, whose clothes and bodies change the room's real absorption.
Runs on: no computer. a scale room model with shifted-frequency sound; a physical device, no digital computing at allSince: 1934 Spandöck's scaled room-acoustic model experiments, Germany
Hele-Shaw cell
Fluid squeezed between two close plates, so flow around obstacles is seen as a flat picture of streamlines.
Question it answers: How does fluid flow around this shape, drawn as a flat picture?
Leaves out: It represents only slow two-dimensional flow.
Runs on: no computer. a bench apparatus, no computationSince: 1898 by 1898, Hele-Shaw's study of flow between parallel plates source
Hanging-chain arch model
A chain or string hung from fixed points takes a shape that, inverted, is the ideal line of a masonry arch.
Question it answers: What shape lets an arch stand using only compression?
Leaves out: It solves one load case at a time.
Runs on: no computer. a hung model, no computationSince: 1675 by 1675, Hooke's anagram on the arch, later used by designers sourceIn the simulations tree: Hooke’s hanging chain
Soap film minimal-surface models
A wire frame dipped in soap solution forms a film whose surface settles to the smallest area.
Question it answers: What surface of least area spans this boundary?
Leaves out: Films find one surface and cannot show competing ones.
Runs on: no computer. a bench apparatus, no computationSince: 1873 by 1873, Plateau, Statique expérimentale et théorique des liquides source
Mechanical differential analyser
Spinning wheel-and-disc integrators linked by rods and gears, set up by hand to solve a particular set of differential equations.
Question it answers: How does this system evolve over time, given the equation that governs it?
Leaves out: Being reusable without rebuilding the linkage for the next problem.
Runs on: no computer. a room-sized mechanical linkage of wheels and discs; a physical device, no digital computing at allSince: 1931 Vannevar Bush's mechanical differential analyser, MIT
Tide-predicting machine
Pulleys and gears summing dozens of known tidal cycles by hand-cranked mechanism, to print out a year of predicted tide heights.
Question it answers: How high will the tide be in this port, on a given day next year?
Leaves out: Storm surge and anything not already in its measured tidal cycles.
Runs on: no computer. a hand-cranked pulley-and-gear machine; a physical device, no digital computing at allSince: 1872 Kelvin and Roberts's harmonic tide-predicting machineIn the simulations tree: Kelvin’s tide predictor
Hydraulic economy model
Coloured water pumped through tanks, valves and pipes standing for income, tax, savings and spending in a national economy.
Question it answers: What happens to spending and stock levels if this tax rate changes?
Leaves out: Expectations and behaviour: the water does not anticipate the next valve turn.
Runs on: no computer. a room-sized network of tanks and pipes; a physical device, no digital computing at allSince: 1949 Bill Phillips's hydraulic model of the economy, London School of EconomicsIn the simulations tree: Phillips’s hydraulic economy
Electrical network analyser
A room-sized array of scaled resistors, capacitors and transformers wired to mimic a power grid, dialled to test a fault or a new line.
Question it answers: What happens to voltage and current across the grid if this line trips?
Leaves out: Anything on the real grid that was not patched into the model that day.
Runs on: no computer. a wired room of scaled electrical components; a physical device, no digital computing at allSince: 1925 MIT's alternating-current network analyser for power-grid studies
Mechanical harmonic analyser
A geared instrument that traces a curve, such as recorded tide or wave data, and reads off the strength of its underlying cycles.
Question it answers: What regular cycles is this messy, real-world curve actually made of?
Leaves out: Anything in the data that is not a clean repeating cycle.
Runs on: no computer. a traced-curve mechanical instrument; a physical device, no digital computing at allSince: 1876 Kelvin's mechanical harmonic analyser
Analogue fire-control computer
Gears and cams combining a ship's own course and speed with a target's bearing to point guns at where it will be, not where it is.
Question it answers: Where should the gun point now, to hit a moving target later?
Leaves out: Any manoeuvre the target has not yet begun.
Runs on: no computer. a mechanical gear-and-cam calculator; a physical device, no digital computing at allSince: 1912 the Dreyer table mechanical fire-control computer, Royal Navy
Galton board
Balls drop through rows of pegs and pile into a bell-shaped curve, showing how many small chances add up.
Question it answers: What spread results when many small random steps combine?
Leaves out: It shows one distribution and cannot change its rules.
Runs on: no computer. a bench apparatus, no computationSince: 1874 by 1874, Galton's quincunx shown at the Royal Institution source
Buffon's needle
Dropping a needle on ruled lines and counting how often it crosses gives an estimate of pi, a hand-run Monte Carlo experiment.
Question it answers: Can random throws estimate a number?
Leaves out: It is inefficient: the estimate improves only slowly with more throws.
Runs on: no computer. hand throwing, no computationSince: 1777 by 1777, Buffon's needle problem in his Essai d'arithmetique morale source
Iron wire nerve model
A passive iron wire in acid carries a travelling surface change that fires, recovers and can be re-triggered like a nerve impulse.
Question it answers: Can a nerve impulse be reproduced by a non-living system?
Leaves out: It copies the pattern, not the ion channels that cause it.
Runs on: no computer. a bench apparatus, no computationSince: 1920 by 1920, Lillie, iron wire as a model of recovery processes in living protoplasm source
Cybernetic tortoises
Small wheeled robots with a few valve circuits that seek light, avoid obstacles and return to a charger.
Question it answers: Can a few parts produce lifelike behaviour?
Leaves out: The behaviours are few and cannot learn beyond simple conditioning.
Runs on: no computer. a two-valve circuit, no computationSince: 1948 by 1948, Grey Walter's Machina speculatrix, Elmer and Elsie source
Sand table
A shallow tray of sand shaped into the hills, rivers and roads of a real or imagined battlefield, used to brief and plan around.
Question it answers: How does the ground itself shape what is possible here?
Leaves out: The weather, the enemy's plan, and anything below the scale of the sand grains.
Runs on: no computer. a shaped tray of sand; a physical device, no digital computing at allSince: 32 by 32 CE, Ma Yuan modelled mountains and valleys in rice for Emperor Guangwu (Book of the Later Han); Reisswitz's damp-sand table followed in 1811 source
Staff ride
Officers walking the actual ground of a historical battle, working through the decisions the original commanders faced at each spot.
Question it answers: Given what is visible from this position, what would have been ordered?
Leaves out: The fear, fatigue and confusion the original commanders actually felt.
Runs on: no computer. a real battlefield walked on foot; a physical device, no digital computing at allSince: 1906 Eben Swift's staff rides at the US Army's Fort Leavenworth
Dress rehearsal
A full run-through of a performance, ceremony or launch, in costume or full procedure, with everything except the real audience or stakes.
Question it answers: Does the whole procedure function, from start to finish, under realistic conditions?
Leaves out: The nerves and the unrepeatable feeling of the real occasion.
Runs on: no computer. a full run-through with real people and props; a physical device, no digital computing at allSince: 1828 by 1828, the term recorded for a full theatrical run-through
Fire and evacuation drills
Everyone in a building or ship actually leaving by the planned routes when an alarm sounds, timed and watched for bottlenecks.
Question it answers: Can all occupants evacuate in time by the planned routes?
Leaves out: Smoke, panic and blocked exits, which are precisely what distinguish real fires.
Runs on: no computer. a real building or ship, evacuated for practice; a physical device, no digital computing at allSince: 1912 by 1912, mandatory lifeboat and fire drills on passenger ships
Mock trial
A rehearsed courtroom proceeding, argued by real or trainee lawyers in front of a judge and jury, to test a case before it counts.
Question it answers: How will this argument, and this witness, actually play in front of a jury?
Leaves out: The real verdict's consequences, for everyone involved.
Runs on: no computer. a rehearsed courtroom with real people; a physical device, no digital computing at allSince: 1400 by 1400, moots held at London's Inns of Court
Military field exercises
Real troops manoeuvring against each other on real terrain, using blank ammunition or safety equipment in place of live weapons.
Question it answers: Can this unit actually execute the plan against people trying to stop it?
Leaves out: Real casualties and the worst of real terrain and weather, by agreement.
Runs on: no computer. real troops on real terrain; a physical device, no digital computing at allSince: 100 by 100 CE, Josephus's account of Roman training manoeuvresIn the simulations tree: Roman drill as rehearsal
Anatomical models
Detailed wax, wood or papier-mache replicas of the body's organs and layers, built for teaching anatomy without a real cadaver.
Question it answers: What does the inside of a body actually look like, layer by layer?
Leaves out: Individual variation: every model shows one idealised body, not the one on the table.
Runs on: no computer. a hand-built wax or wood replica; a physical device, no digital computing at allSince: 1780 Clemente Susini's wax anatomical models, Florence
Obstetric phantom
A life-sized pelvis and infant model used to teach midwives to handle a difficult birth by feel, before ever attending a real one.
Question it answers: Can this trainee deliver a baby safely when something goes wrong?
Leaves out: The mother's condition and any complication not built into the model.
Runs on: no computer. a stitched fabric and leather training mannequin; a physical device, no digital computing at allSince: 1756 Angelique du Coudray's obstetric training mannequin, FranceIn the simulations tree: Du Coudray’s birth mannequin
Early resuscitation manikins
A simple mannequin chest and airway that a trainee breathes into and presses on, giving basic feedback on technique.
Question it answers: Is this person pressing hard enough and giving enough breaths to keep someone alive?
Leaves out: Almost everything about a real emergency except the two actions being drilled.
Runs on: no computer. a simple mechanical training mannequin; a physical device, no digital computing at allSince: 1960 the first mass-produced CPR training manikin, Norway
Crash-test dummies
Instrumented mannequins with human-like mass and joints, strapped into a real vehicle and driven into a real barrier.
Question it answers: How hard would a real body be hit in this exact crash?
Leaves out: The variation between real bodies: one dummy design stands in for everyone.
Runs on: no computer. an instrumented mannequin in a real vehicle; a physical device, no digital computing at allSince: 1949 the first anthropomorphic test dummy, for US aviation ejection-seat testing
Moulage
Realistic wounds, burns and rashes painted or moulded onto actors or manikins, used to train medics and triage teams to recognise conditions fast.
Question it answers: Can this responder correctly read and prioritise what they are looking at?
Leaves out: The patient's actual physiology underneath the painted surface.
Runs on: no computer. painted wax or makeup on a person or manikin; a physical device, no digital computing at allSince: 1867 Jules Baretta's dermatological wax moulages, Paris
Ballistic gelatin blocks
Blocks of gelatin calibrated to match the density of muscle tissue, shot to study how a bullet or fragment behaves once inside a body.
Question it answers: How far does this round travel, and what shape of path does it leave, in tissue?
Leaves out: Bone, skin and clothing unless layered in on purpose.
Runs on: no computer. a calibrated gelatin block; a physical device, no digital computing at allSince: 1945 wartime wound-ballistics researchers testing rounds in gelatin blocks
Automata
Mechanical figures of people and animals that move, play instruments or mimic life, driven by weights, cams or gears.
Question it answers: Can a machine imitate a living body?
Leaves out: They replay a fixed routine and cannot respond to the world.
Runs on: no computer. a clockwork, no computationSince: 50 by the mid-1st century CE, Hero of Alexandria's Automata describes self-moving figures and theatres; the earliest instrument-playing machine is the Banū Mūsā's flute player (9th century, Baghdad) source
Motion platforms
A moving seat or cabin that tilts and shifts so the occupant feels the movements of a vehicle.
Question it answers: What does the occupant feel when the vehicle moves?
Leaves out: Platforms can only hint at sustained acceleration.
Runs on: no computer. a mechanical rig, no computationSince: 1910 by 1910, the Sanders Teacher, a model aircraft joined to the ground by a universal joint source