Page 19 - Inventions - A Visual Encyclopedia (DK - Smithsonian)

IN THE RIGHT The compass’s The device is held by this ring.
DIRECTION needle works
only if it can
The compass was spin freely. NAVIGATING SEAS
invented in China in the Early mariners calculated
3rd century bce. Modern their position at sea with a
instruments have a device called an astrolabe that
magnetized needle at the measured the angle between
center that works with objects in the sky, such as the
Earth’s magnetic field, so moon, and the horizon. Ancient
it always points to the Greeks may have designed early
north. Early compasses Chinese compass, astrolabes around 200 bce and
mid-19th century
pointed south. From the they were definitely in use by the
11th century ce, sailors began 7th century ce. The astrolabe was
to use the compass at sea. then improved by Muslim EARLY BREAKTHROUGHS
astronomers who used
it to find the direction
Scale to measure
the altitude of of Mecca, their
stars or planets holiest city.
above the horizon

▼ MARINER’S ASTROLABE Rotating pointer
Invented in the 16th century ce, fixed to the center
this device gave accurate readings
on board ships at sea.

Viewing hole
through which the
stars were observed

Heavy bottom to keep
the device stable

17

US_016-017_Sailing_the_seas_Main.indd 17 08/03/18 3:09 PM