Finding the way at sea

15 steps · 63,000 BCE – 1978

Setting out to sea is easy; coming back is not. Stars, magnets, maps, clocks and satellites: how we learned to know where we are when the coast is out of sight.

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1
c. 65 ka · Madjedbebe Shelter, Arnhem Land, Australia · Invention or technique
Open-sea crossing to Sahul (watercraft)
At least 50,000 years ago, perhaps 65,000, humans cross tens of kilometres of open sea to Australia. It is the first sea crossing we know of.
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2
c. 3500 BCE · Naqada and Gerzeh, Upper Egypt, Egypt (depictions); the Persian Gulf · Invention or technique
Sail and sailing boat
The sail appears on the Nile: wind replaces oars. Boats can go further with fewer people, always within sight of the shore.
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3
c. 1000 BCE – 1250 CE · Tonga and Samoa (origin of the Polynesian expansion) · Discovery
Settlement of Polynesia and star navigation
With no instruments, Polynesian navigators read stars, swells, clouds and birds to settle a whole ocean, from Tonga to Hawaii, Rapa Nui and New Zealand.
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4
c. 280 BCE · Pharos Island, Alexandria, Egypt · Invention or technique
Lighthouse of Alexandria (Pharos)
The Lighthouse of Alexandria, one of the wonders of the world, guides ships into the harbour at night. The coast begins to be marked for sailors.
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5
c. 900 · Baghdad, Iraq (al-Fazari, al-Khwarizmi) · Scientific instrument
Islamic planispheric astrolabe
The astronomers of Baghdad perfect the astrolabe, which measures the height of the stars. Its nautical version will let sailors find their latitude at sea.
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6
c. 1100 · Guangzhou / Kaifeng, Song China · Invention or technique
Magnetic navigational compass
Chinese sailors use a magnetised needle to find their bearings under overcast skies. The compass reaches the Mediterranean in the twelfth century.
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7
c. 1290 · Pisa / Genoa, Italy (Carta Pisana) · Invention or technique
Portolan chart
With the compass come portolan charts: accurately drawn coasts and a web of rhumb lines to plot a course from port to port.
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8
c. 1440 · Lagos and Sagres, Algarve, Portugal · Invention or technique
Caravel
The Portuguese develop the caravel, light and able to sail close to the wind. In it they work down the African coast and learn to return by looping through the open ocean.
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9
1519-1522 · Strait of Magellan, Chile · Expedition or mission
First circumnavigation of the globe
Magellan's expedition, completed by Elcano, sails around the world. Only one ship in five returns, but it proves that all the oceans are connected.
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10
1569 · Duisburg, Germany · Invention or technique
Mercator projection
Mercator projects the globe so that a constant bearing is a straight line on the map. It distorts areas, but it is the ideal chart for navigating.
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11
1594 · Sandridge, Devon, England · Scientific instrument
Davis quadrant
The explorer John Davis designs a quadrant to measure the Sun's height with his back to it, without being dazzled. Latitude is measured better.
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12
1731 (octante) / 1757 (sextante) · London, England / Philadelphia (Godfrey) · Scientific instrument
Octant and sextant
Hadley's octant, and then the sextant, use mirrors to line up horizon and star even on a moving deck. Latitude is solved.
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13
1735 (H1) / 1759 (H4) · Barrow upon Humber / London, England · Invention or technique
Marine chronometer
Longitude remains, and it requires knowing the exact time at the home port. Harrison's clock keeps time at sea to within seconds a day.
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14
1935 · Daventry, England · Invention or technique
Radar
Radar sees the coast, other ships and storms at night and in fog. Born for air warfare, it transforms navigation too.
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15
1978-1995 · US Department of Defense; Vandenberg Air Force Base (first Navstar, 1978); Rockwell and Aerospace Corporation, El Segundo, California · Invention or technique
Global Positioning System (GPS)
A constellation of satellites carrying atomic clocks gives your position anywhere on Earth to within metres. From the Polynesians' starry sky to an artificial one.
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