The time is indicated where a shadow or light falls on the dial face, which is usually inscribed with hour lines. Although usually straight, these hour lines may also be curved, depending on the design of the sundial (see below).
Source: National Institute of Standards and Technology Physics Laboratory Not until somewhat recently (that is, in terms of human history) did people find a need for knowing the time of day. As best we know, 5000 to 6000 years ago great civilizations in the Middle East and North Africa initiated clock-making.
Parts of a Sundial: Gnomon: The shadow caster, in a horizontial dial the angle phi is equal to the Latitude of the location. Hour Line(s): The numbered lines that the shadow falls along. Nodus: A "marker" along the gnomon to get an exact point on the shadow.
Such a sundial will however work equally well at all times if the pointer is slanted, to point towards the pole of the celestial sphere (click here for an explanation--but be warned, it is a bit complicated!). The angle between it and the base then equals the geographic latitude of the user.
Sundials have been used for thousands of years to tell time. You can make this simple horizontal sundial in just an hour or two. Use a disk made from wood or heavy cardboard for the base of your sundial. Mark its center with a pen or pencil.
Sundial Seashells Family: Architectonicidae. You wont be able to tell time from these shells, but this shell is a treasure in any collection. This small family features a rather flattened shell with either beaded or smooth surfaces. The bottom of the shell is concave and resembles a staircase.
Sundials began as fairly simple devices, but as time passed they became more complex. Let's take a step back and examine some basic astronomy. The Earth rotates around the sun, but it does so in an elliptical (oval) orbit, not a circular one.
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