Sundials, Water Clocks, Pendulums & Humanity’s Quest to Measure Time
From the shadow of a gnomon sweeping across ancient stone to the vibration of cesium atoms defining the modern second, timekeeping is one of humanity’s most enduring obsessions. These ten interactive simulations trace that journey—each demo lets you manipulate the physics, adjust the parameters, and watch time-measuring devices come alive.
The earliest timekeepers used natural phenomena—shadows, flowing water, burning wax and incense—to divide the day into measurable intervals.
A horizontal sundial with a latitude-adjustable gnomon. Drag the sun across the sky and watch the shadow sweep hour lines calculated from real trigonometry.
An ancient Egyptian outflow water clock governed by Torricelli’s law. Adjust orifice size and vessel shape to see how flow rate changes with water height.
A particle-based sand hourglass simulation. Watch granular flow through the neck, with Janssen-effect constant flow rate. Click to flip it over.
King Alfred’s candle clock: a burning candle with hour markings. Adjust burn rate and wind to see how medieval timekeeping worked by firelight.
A Chinese dragon-boat incense clock with silk threads and bells. Watch the incense burn through marked intervals and trigger chiming alarms.
The pendulum revolution: from Huygens’ cycloidal cheeks to Harrison’s sea-going chronometer, mechanical ingenuity transformed timekeeping precision.
Huygens’ 1656 masterpiece: a pendulum with cycloidal cheeks for isochronism. Compare circular vs. cycloidal paths and see why the cycloid wins.
The heartbeat of every mechanical clock. Watch the anchor pallets engage and release the escape wheel tooth by tooth, delivering precise impulses.
Harrison’s H4 solved the longitude problem. Adjust temperature and watch the bimetallic compensation curb keep the balance spring accurate at sea.
From Foucault’s swinging proof of Earth’s rotation to the cesium atom’s quantum heartbeat—timekeeping at the frontier of physics.
Léon Foucault’s 1851 proof that Earth rotates. Adjust latitude and watch the swing plane precess at Ω·sin(φ). Pegs topple as Earth turns beneath.
Cesium-133’s hyperfine transition defines the second at 9,192,631,770 Hz. Tune the microwave frequency and watch the detector signal peak at resonance.