Aristarchus of Samos invented this type of sundial. It is in the form of a concave bowl, but is not like the usual sundial because it is hemispherical in shape, rather than circular.
It has a marker (gnomon) that keeps pace with half of the diameter. By means of this marker the position and height of the sun can be calculated by observing the shadow of the marker and its position on the lines marked on the bowl.
Aristarchus theorized that the Earth and planets revolve around the Sun, which debunked Aristot's principle that all objects revolve around the Earth.
Aristarchus did not hesitate for one moment in accepting such an apparently irrational hypothesis. In fact, it takes much fantasizing to imagine the challenge of such a hypothesis
|BIBLIOTHECA ALEXANDRINA ANTIQUETIES MUSEUM [01/027] ALEXANDRIA BAAM