Sundial
device · 1500 BC · Ancient world
Telling time by the shadow of a gnomon.
What it is made of
- Sundial gnomon — has part. A rod that casts a shadow.
- Clock dial — has part. A marked plane with hour lines.
Principles and materials it uses
- Stone — is made of. Sundials were hewn from stone.
- Euclidean geometry — uses. The scale is marked by the angle of the shadow.
Where it is used
- Calendar — is used in. Calendar observations relied on the movement of the gnomon’s shadow.
Things built in a similar way
- Water clock (clepsydra) — works like. Two ancient ways to measure time: by a shadow and by flowing water.