Scaphe
Ancient Greek hemispherical sundial, commonly attributed to later astronomers such as Berossus.
The scaphe (from the Ancient Greek σκάφη, meaning "bowl," and also called a skaphe, scaphion, or scaphium in Latin) is a type of sundial more commonly attributed to later Greek astronomers such as Berossus or described by the Roman architect Vitruvius, rather than to Aristarchus of Samos. The device featured a hemispherical bowl with a vertical gnomon positioned inside, its top aligned with the bowl’s rim. Twelve hour markings were carved perpendicularly into the hemisphere to track the time of day. No original works by Aristarchus remain, but later records and illustrations describe its form; his original would have been made of stone.
Aristarchus, who lived from around 310 to 230 BC, is known for proposing the first known heliocentric model of the universe, placing the Sun at the center with Earth and the other planets orbiting it. However, ancient sources do not specify that he correctly ordered all planets by distance as we know them today. Additionally, the concept of a "central fire" was introduced by Philolaus of Croton, who placed a central fire (not the Sun) at the center of his system, a notion distinct from Aristarchus's heliocentric model. His ideas were largely rejected in favor of the geocentric systems of Aristotle and Ptolemy.
In Greek and Roman times, large stone sundials based on a partial sphere or scaphe were common. The tip of the gnomon’s shadow served as the time indicator, and these dials could theoretically give accurate readings if carved to a true sphere and calibrated for a specific location. However, crafting such a dial required a skilled stoneworker, considerable time, and significant expense, limiting them to wealthy citizens who placed them in villas or donated them to town forums. Cheaper, simpler dials were needed for ordinary laborers, but even then, calibrating the scaphe remained a challenge.
The problem of projecting the three-dimensional scaphe onto a vertical or horizontal plane was tackled by several 19th-century mathematicians, each apparently satisfied with their own solution. Yet their published works were so complex, lengthy, and obscure that they remained largely inaccessible to antiquarians and, judging by repeated efforts, even to their own colleagues. The underlying spherical trigonometry is actually straightforward, though the calculations are tedious rather than difficult. Modern computer-generated graph
- inventor
- Attributed to later Greek astronomers (e.g., Berossus) or described by Vitruvius
- century
- 3rd century BC (earliest known examples)
- field
- Astronomy, mathematics
- known_for
- Hemispherical sundial design; not directly invented by Aristarchus
- material
- Stone (original)
Lore & Background
The scaphe was a hemispherical bowl with a vertical gnomon whose shadow fell on twelve hour gradations. Greeks and Romans used large stone sundials based on a partial sphere or scaphe, with the shadow of the tip of the gnomon serving as the time-telling index. These dials could in theory tell time accurately if carved to a true sphere and correctly calibrated for a given site. The scaphe is often attributed to later astronomers like Berossus or described by Vitruvius, not Aristarchus.
Reader's Guide
The scaphe represents an early attempt at precise timekeeping using geometry and astronomy. Its invention is credited to Aristarchus of Samos, who also proposed the first known heliocentric model of the solar system. The device required skilled stonework and was expensive, limiting its use to wealthy citizens. Later mathematicians in the 19th century attempted to project the three-dimensional scaphe dial onto vertical or horizontal planes, but their publications were complex and obscure. The advent of computer-generated graphics and Fortran programming eventually allowed for easier plotting of such dials for any latitude. The scaphe's legacy lies in its combination of practical time measurement with theoretical astronomy, though no original examples survive.
Did You Know?
- The scaphe is also known as a skaphe, scaphion, or scaphium.
- The scaphe is more commonly attributed to later Greek astronomers like Berossus or described by Vitruvius, not Aristarchus of Samos.
- Only wealthy citizens could afford a stone scaphe, often for villas or as donations in town forums.
- A Fortran program was written at the University of Leicester to plot vertical or horizontal scaphe dials for any latitude.
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