Transport & space · c. 1481

Mariner's astrolabe

A heavy brass ring lets sailors measure the Sun's height and find their latitude.

Portuguese navigators simplified the scholar's astrolabe into a rugged open ring for use at sea by the 1480s. Measuring solar altitude at noon, combined with declination tables, gave latitude. It guided Dias and da Gama around Africa and into the Indian Ocean.

See it in the living tree Wikipedia

Arcs above join it to what it stood on, arcs below to what it led to. The bar places this stretch on the tree's whole timeline.

What it built on 2

Magnetic compass 1040
Euclid's Elements 300 BCE

What it led to 2

First circumnavigation 1522
Sextant 1757

Related measurements

The dashed line marks when it first worked.

Transatlantic crossing time Latest: 3.5 hours (1976) Source: Wikipedia: Transatlantic crossing, duration list; Geography of Transport Systems: liner transatlantic crossing times

World trade as a share of GDP since 1500 Latest: 1950-now (PWT): 57.8 % of GDP (2023) Source: Our World in Data