Galileo's Instruments of Discovery- page 4 | Science | Smithsonian
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Galileo Galilei invented the geometric and military compass. It was his first commercial scientific instrument. (Franklin Institute)

Galileo's Instruments of Discovery

With these various instruments, Galileo Galilei was able to look into space and change our view of the universe.

Nocturnal and Sundial

Galileo nocturnal and sundial
(Franklin Institute)

During the day, a person could tell time with this pocket-size device by unfolding a gnomon, a vertical shaft, and thereby turning the device into a small sundial. Turn it over at night, line it up with the pole star, Ursa Major, and it became a nocturnal. At night, the sky appears to revolve around the pole star, and though the stars’ positions vary by time of year, they can give an indication of time during the night. A nocturnal could be manipulated to help a person determine the local time based on these star positions. This nocturnal and sundial device dates to 1554.

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