An interactive handbook · nine rooms
Reckoning
Measure, shape, number, sky, weather, signal, ship, code and light: the reference tables a navigator, engineer or student reaches for, made into instruments you can use. Every value is traced to a current primary standard, and every formula is checked by computer each time the site is built.
Rooms
Measure
Units, their exact definitions, and a converter that says where every factor comes from.
Shape
Areas and volumes of 42 figures and solids, each formula checked, with a topology lens.
Number
Symbols, Greek letters, trigonometry on the unit circle, logarithms and a working slide rule.
Sky & sea
Latitude and longitude on a globe, great circles against rhumb lines, the kinds of time.
Weather
The Beaufort scale with an animated sea, sea state, visibility, weather symbols, tropical cyclones.
Signal
Code flags, Morse with sound and correct timing, phonetic alphabets, sound signals.
Ship
A hull cutaway with every named part, buoyancy, and a stability simulator.
Code of life
DNA bases and pairing in 3D, the IUPAC letters, and supercoiling as topology.
Light
An optical bench: rays traced exactly through lenses, prisms, mirrors and a raindrop.
Reference
Glossary
Nautical terms in English, Spanish and French, and words that mean different things in different rooms.
Names from the sky
The gods behind the planets, their moons, the days of the week, the months and a dozen elements.
How it is checked
The rules, the automatic checks that ran for this build, and every primary source.
Start here
Convert anything
Results are exact when both units are defined exactly and the decimal ends. Otherwise they are rounded to 15 significant figures and marked with an ellipsis.